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Industry Circles => Tortuga Audio => Topic started by: tortugaranger on 1 Dec 2016, 12:59 am

Title: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 1 Dec 2016, 12:59 am
As development on the V3 continues I thought it was time to start a topic dedicated to this successor to our V2 (V2.1) preamp controller.

One of my key goals for 2016 was to release the V3 before the end of the year but that is not going to happen. Still, we are making progress albeit slower than planned. No small part of the delay is the ambitious nature of the V3 which involves a significant amount of software development that among other things includes moving to a newer and more powerful processor, a complete new hardware architecture, and porting the existing code from Pascal to C. That porting was completely months ago, we are several hardware prototypes down the road and a huge amount of software development work has been completed.

To give you some perspective on the V3 software development, the total code size for the V2 occupies around 24k bytes of compiled code. The compiled V3 code is already over 50k and is likely to reach 60k before it's fully cooked.

A few days ago we celebrated a major software/hardware development milestone. The V3 successfully downloaded an updated firmware image over the internet from an offsite website server using a wireless WIFI link, stored the firmware image in the V3's EEPROM memory chip, and then performed a system reset where a separate bootloader program (another 4k bit of code) loaded the stored image from EEPROM storage memory into the processor's active "flash" memory effectively self-updating its own firmware all hands-off without user intervention. Way cool stuff!!!  :thumb:

There's no doubt in my mind that audio is moving inexorably towards the "internet of things". The V3 intends to be part of that even if only in a small way at first. It's easy to get lost in all the tech at times but the overall goal is a better sounding LDR preamp that represents outstanding value in high performance audio. We are getting closer!

Cheers,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: vvoid on 14 Jan 2017, 06:14 pm
Hi, just signed up here. I was searching the web for possible preamp-choices for my needs and stumbled over Tortuga, which I hadn't known before. I think the company is fairly unknown in Germany, so that probably explains why.

After reading some articles on the website and of course also here, I'm quite impressed by the way this company presents itself. Very transparent explanations, even technical, "internal" stuff is disclosed without hesitation, no secrets, no voodoo, no obscure/esoteric stuff involved, great! Also, from reading on this forum, Morton seems like a very open guy with the correct attitude. I like that, so I'm seriously considering getting one of these preamps in the future. Oh, and the products themselves also earn nothing but praise, but to be fair, I've never heard any.

Anyway, enough praise, I've got a question. ;)

You know, for me the feature list of the LDR3.V2 is spot on and seems to satisfy everything I could ever want/need in a preamp, would it not be for one thing: The distinction between a balanced and unbalanced version. I have sources, or might have in the future, which have balanced outpus, whereas others are strictly single-ended. It's just not practical to have a preamp limiting one to either unbalanced _or_ balanced. We need both.
   
The question is, how are you planning it for the V3?
Apparently the V3 is more modular in design, so maybe it would be possible to generally offer customers the option to choose how many XLR and RCA in-/outputs they want? For inputs this choice would be more important, outputs could be fixed at maybe one pair of RCAs and one pair XLR, if too complicated otherwise. Maybe it could even be combined somehow? I mean user-switchable outputs, where 4 RCA's could be combined into 2 XLR... (so you go from 2 stereo-outputs to only 1 in this example)

I think it would be really nice and the correct step to improve flexibility. After all, flexibility plays a very important part in choosing preamps, at least for me it does. Heaven knows what new devices I'm going to get myself in the coming years, so I need the flexibility in connections. I'm curious what others think?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: kernelbob on 14 Jan 2017, 07:07 pm
Hi vvoid,

I run a biamplified system and use the LDRxB-V2 for my main controller and an LDR1B-V2 as a level matching attenuator ahead of the bass amps.  I run an all balanced system, so mixing balanced and single ended inputs or outputs isn't an issue for me.  The LDRxB does, though, include one single ended input and output.  The single ended signal is converted to/from balanced since the internals of both units are balanced.  Though I don't normally use the SE inputs/outputs, it's nice to know that they're available if I would need them.  You can mix balanced/single-ended inputs and outputs.  In my case, I could drive a single ended mid/treble amp and a balanced bass amp if needed or switch between a balanced DAC input to a single ended phono stage input.

The Tortuga controllers' signal path is indeed simple, which is one of the main reasons for the purity of it's performance.  The sonic "secret sauce" is that there are no switches or potentiometers in the signal path with both attention level and input selection performed by LDRs (light dependent resistors).  I would not want to see various switches added for additional configuration flexibility at the cost of that sonic purity.

This is not to say that the Tortuga LDR controllers are simple devices.  There is a lot of software complexity that gives you a level of control that I haven't seen in any other preamp controller.  These features include the opportunity to recalibrate the attenuation steps any time you want with the press of a button on the remote.  This way, any long term drift in the LDR's attenuation curve is a non-issue.  You can also select any input impedance setting from 1k to 99k (single ended) or 2k to 198k (balanced) and save up to five input impedances, from which you can select using the remote any time you want.  Morten's even implemented absolute phase switching from the remote in the balanced units... still without adding any complexity in the signal's path.  That's a feature that I would now not want to be without.

No preamp/controller is going to be all things to all customers.  I've heard the Tortugas trounce preamps costing five figures and with controls (that matter) that I haven't seen elsewhere.

Robert

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: vvoid on 15 Jan 2017, 09:05 am
Hi Robert, thanks for reply.
Yeah, the LDRxB does provide XLR+RCA in/outputs, so that's good. The question is which configurations are going to be available for the upcoming LDR.V3...

I thought maybe there is still time to put something on our wishlist!  :D
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 15 Jan 2017, 05:51 pm
Hi, just signed up here. I was searching the web for possible preamp-choices for my needs and stumbled over Tortuga, which I hadn't known before. I think the company is fairly unknown in Germany, so that probably explains why.

After reading some articles on the website and of course also here, I'm quite impressed by the way this company presents itself. Very transparent explanations, even technical, "internal" stuff is disclosed without hesitation, no secrets, no voodoo, no obscure/esoteric stuff involved, great! Also, from reading on this forum, Morton seems like a very open guy with the correct attitude. I like that, so I'm seriously considering getting one of these preamps in the future. Oh, and the products themselves also earn nothing but praise, but to be fair, I've never heard any.

Anyway, enough praise, I've got a question. ;)

You know, for me the feature list of the LDR3.V2 is spot on and seems to satisfy everything I could ever want/need in a preamp, would it not be for one thing: The distinction between a balanced and unbalanced version. I have sources, or might have in the future, which have balanced outpus, whereas others are strictly single-ended. It's just not practical to have a preamp limiting one to either unbalanced _or_ balanced. We need both.
   
The question is, how are you planning it for the V3?
Apparently the V3 is more modular in design, so maybe it would be possible to generally offer customers the option to choose how many XLR and RCA in-/outputs they want? For inputs this choice would be more important, outputs could be fixed at maybe one pair of RCAs and one pair XLR, if too complicated otherwise. Maybe it could even be combined somehow? I mean user-switchable outputs, where 4 RCA's could be combined into 2 XLR... (so you go from 2 stereo-outputs to only 1 in this example)

I think it would be really nice and the correct step to improve flexibility. After all, flexibility plays a very important part in choosing preamps, at least for me it does. Heaven knows what new devices I'm going to get myself in the coming years, so I need the flexibility in connections. I'm curious what others think?

Thank you for the thoughtful note. And welcome to AudioCircle.

Your suggestions are well received. Fully accommodating both balanced and SE audio in a single unit inevitably takes up more real estate than either by itself. And the possible permutations get quite large. Offering up customized solutions would mean we could never really have enough of the right finished parts on hand. Making one-off customized parts gets very costly and very slow. We've done some of that. The problem comes down to there not being enough hours in the day unless prices are increased substantially.

Another consideration with mixed signal types is do you keep both separate or provide conversion from SE to truly balanced and if so do you use transformers or go solid state. All of which piles on cost, more hardware, which then needs more space.

That all said, we are looking at alternatives for the successor to the LDRxB and will keep your suggestions in mind as we do so.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: vvoid on 16 Jan 2017, 06:45 pm
Thanks, your considerations concerning possible permutations and finished parts makes sense. A fully customizable model probably goes too far...
How about:

1. Unbalanced version: In/Outs like LDR3.V2, that's perfect.

2. Balanced version: Here it starts to get difficult. Just 1 pair of inputs (like the LDR1B.V2) hardly makes sense imo. Sorry, but a preamp should provide means to connect multiple devices. Else it's really just a fancy "line attenuator" and I'm thinking most people need some additional switching device. How else to manage?

3. Combined version, like for example:
Inputs: 1 pair XLR, 2 pair RCA
Outpus: 1 pair XLR, 1 pair RCA
Or whatevever combination technically would be the simplest to realize. Hmm, ok, I just realize it really boils down to a new LDRxB, just as you said, lol.

Maybe the new "standard" balanced version could (relative) easily be extended by additional RCA inputs...?
(I'm wondering how your sales figures concerning the proportion of sold preamps is? I'd suspect unbalanced tops, followed by LDRxB and then, by a large margin, the LDR1B.V2. Then again, I might be totally wrong... ;))
But, alright, whatever, I'm surely keeping an eye open on what the lineup for V3 is going to be.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 16 Jan 2017, 08:49 pm
Thanks, your considerations concerning possible permutations and finished parts makes sense. A fully customizable model probably goes too far...
How about:

1. Unbalanced version: In/Outs like LDR3.V2, that's perfect.

2. Balanced version: Here it starts to get difficult. Just 1 pair of inputs (like the LDR1B.V2) hardly makes sense imo. Sorry, but a preamp should provide means to connect multiple devices. Else it's really just a fancy "line attenuator" and I'm thinking most people need some additional switching device. How else to manage?

3. Combined version, like for example:
Inputs: 1 pair XLR, 2 pair RCA
Outpus: 1 pair XLR, 1 pair RCA
Or whatevever combination technically would be the simplest to realize. Hmm, ok, I just realize it really boils down to a new LDRxB, just as you said, lol.

Maybe the new "standard" balanced version could (relative) easily be extended by additional RCA inputs...?
(I'm wondering how your sales figures concerning the proportion of sold preamps is? I'd suspect unbalanced tops, followed by LDRxB and then, by a large margin, the LDR1B.V2. Then again, I might be totally wrong... ;) )
But, alright, whatever, I'm surely keeping an eye open on what the lineup for V3 is going to be.

Query - Do RCA inputs have to be output to the XLR outputs as well as the RCA outputs?  If so, can it be just single phase (fake balanced) or do they have to be converted and output as true balanced signals?

The reason I ask is this complicates things as it requires either a signal conversion transformer or specialized op amps and additional power supply plus the additional real estate to go with it. We used a transformer in the LDRxB.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: kernelbob on 16 Jan 2017, 09:28 pm
Thanks, your considerations concerning possible permutations and finished parts makes sense. A fully customizable model probably goes too far...
How about:

1. Unbalanced version: In/Outs like LDR3.V2, that's perfect.

2. Balanced version: Here it starts to get difficult. Just 1 pair of inputs (like the LDR1B.V2) hardly makes sense imo. Sorry, but a preamp should provide means to connect multiple devices. Else it's really just a fancy "line attenuator" and I'm thinking most people need some additional switching device. How else to manage?

3. Combined version, like for example:
Inputs: 1 pair XLR, 2 pair RCA
Outpus: 1 pair XLR, 1 pair RCA
Or whatevever combination technically would be the simplest to realize. Hmm, ok, I just realize it really boils down to a new LDRxB, just as you said, lol.

Maybe the new "standard" balanced version could (relative) easily be extended by additional RCA inputs...?
(I'm wondering how your sales figures concerning the proportion of sold preamps is? I'd suspect unbalanced tops, followed by LDRxB and then, by a large margin, the LDR1B.V2. Then again, I might be totally wrong... ;))
But, alright, whatever, I'm surely keeping an eye open on what the lineup for V3 is going to be.

Regarding priorities... I have the balanced Tortugas, the LDRxB-V2 and an LDR1B-V2.  One thing that my experience with the Tortugas has taught me is that everything matters and every bit of added complexity has a downside.  For example.  The LDR1B-V2 has a simpler signal path.  Yes, this limits your input to one pair, though it does have two pairs balanced outputs.  Not having to perform input switching duty, the LDR1B doesn't have input switching LDRs, only the series/shunt pair on each phase leg of the signal.  That's it.

By comparison, the LDRxB has three balanced and one SE inputs.  This requires the addition of LDRs on each leg of each balanced input to handle switching.  Otherwise, the attenuation is handled the same way as in the LDR1B.  In an A/B comparison, the LDR1B is just slightly cleaner sounding, just slightly more resolving than the LDRxB.  That's the sonic price that you have to pay to have multiple inputs.

I use the LDRxB as my main controller and the LDR1B using one output from the LDRxB as input and attenuating the level to feed my bass amps.  The other LDRxB outputs connect directly to my M/T amp.

Now, if you're going to run an all digital system, the LDR1B could work just fine with the output of a DAC as input.  If you have multiple digital sources, you could still handle switching between them if your DAC supports multiple inputs.  In my system (I'm using a Schiit Yggy DAC) it could switch between any of these different types of digital sources.  However, there's another solution.  I've found that the "Mutec MC3+USB" clock regenerator makes a huge improvement in my system (especially when powered through the best power cord you can find).  I have the Mutec feeding the reclocked digital input to the Yggy.  The Mutec also allows multiple types of digital inputs, so I switch sources from there.  The allows me to have USB, Toslink, RCA SPDIF, and AES/EBU digital input and to pass the digital output to the Yggy via an AES/EBU balanced cable.

Even though I only use one input connection on the LDRxB, it is still staying in my system thanks to Morten's latest addition of absolute phase switching from the remote.  Morten was very patient with all my advocacy of this feature and his implementation is very elegant... no added complexity to the signal path.  Once you live with this feature in the LDRxB you won't want to be without it.

One last thought, I would strongly argue against using opamps to convert SE to balanced and vice versa.  Using an input and an output transformer in the LDRxB allows all the internal attenuation to be handled in balanced mode just as though it came from a balanced source and/or is feeding a balanced output.  That's my vote anyway.

As far as new features in the coming V3 product, I'm really looking forward to their development, but I hope that the signal path is kept as simple as possible.  I'd hate to see switches start showing up the the V3 or even additional LDRs in the signal path.  Whatever features & complexity gets added to the software is great, but not in the signal path.

Robert
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: vvoid on 16 Jan 2017, 10:05 pm
Query - Do RCA inputs have to be output to the XLR outputs as well as the RCA outputs?  If so, can it be just single phase (fake balanced) or do they have to be converted and output as true balanced signals?

1. I fear yes. It should be possible to output RCA-input to XLR. (and vice versa ideally)
2. Probably would be ok to fake balance in that RCA-input case. (I assume you mean fake in the sense that there's just ground on XLR pin 3?)

Don't get me wrong. In general I fully agree with kernelbob's view that there should be as few things as possible in the signal path. And this really excludes having some opamps inside for creating a truly balanced signal. And transformers are too costly, so... as simple and affordable as possible. But wait, what with XLR-input to RCA output? We'd need something active for that, or is there some other way?

Edit: I just realize your query was only for the case "extend balanced version with RCA inputs".  So, yes and yes, see above. Having additional RCA-inputs is simply better than not having those, there's no drawback.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 16 Jan 2017, 10:27 pm
Don't get me wrong. In general I fully agree with kernelbob's view that there should be as few things as possible in the signal path. And this really excludes having some opamps inside for creating a truly balanced signal. And transformers are too costly, so... as simple and affordable as possible. But wait, what with XLR-input to RCA output? We'd need something active for that, or is there some other way?

There are only 2 ways to convert SE to balanced: 1) active (op amps etc. ), or;  2) transformers.

You can fake it by just putting the SE output on say pin 2 of the XLR and nothing on pin 3. You can't put the ground on pin 3 because it would bugger the normal balanced output. You'd rely on pin 1 being grounded which it usually is.

I've given this some thought and have done a fair bit of research and I'm going to disagree with kernelbob on one point. There are specialized integrated circuits available today that rival transformers for driving balanced output from SE input. An oddly named company called THAT Corporation makes a highly regarded IC (http://www.thatcorp.com/1600-series_Balanced_Line_Driver_ICs.shtml (http://www.thatcorp.com/1600-series_Balanced_Line_Driver_ICs.shtml)) that does an excellent job of it. Extreme low PSRR - low enough that with decent power quality to start with the noise floor due to the driver is in the -100 dB territory, i.e. dead quiet.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 20 Jan 2017, 03:13 pm
Starting a new product version topic for the V2.5 (or V25) version of our preamp controller board.
This topic picks up where the prior LDR3x.V2 preamp controller board topic left off:  http://www.audiocircle.com/index.php?topic=119407 (http://www.audiocircle.com/index.php?topic=119407)

The V2.5 will be replacing the current V2.1 once it's released.

(http://www.audiocircle.com/image.php?id=156623)

For those of you who've been following us of late you may well be wondering.....Wait. What? Aren't you working on coming out with the new "V3" preamp controller?

Yes we are. Work on the V3 continues and much progress has been made.

But as supplies of our existing LDR3x.V2.1 Preamp Controller boards dwindle down we had to make a decision. Commit to ordering a new batch of V2.1 boards with no changes...or...update the V2.1 design based on everything we've learned over the past 2+ years with the V2.1?

Another consideration was the realization that the V3 is going to be a more expensive design geared towards up market products and may not be a good fit for the DIY community. That's all still TBD.

When we added up all the pros and cons we made the decision to update the V2.1 and hence the V2.5...or just V25...was born...or at least conceived.

The V25 does not stray too far from the V2.1 but it also borrows from our work on the V3. The V25 does have a new processor, uses mostly surface mount components and is roughly 30% shorter in length than the V2's. We also did away with the autocal piggy-back board that was on the underside of the V2 board.

Along with the new V25 we are also replacing our existing IO3 relay board with the new IO3LDR input switching board. As its name implies, the new IO3LDR uses 100% plug-in LDRs in lieu of electromechanical relays for input switching.

The PCB layouts of both new boards are shown above. The V25 board is 2.5 x 3.6" and the IO3LDR board is 2.5 x 1.5".

We are making no promises on when the V25 will be released but within 30-60 days is our goal. The IO3LDR is already done and production boards have been ordered.

The V25 will get our full attention over the next few weeks and so work on the V3 has been put on hold until the V25 is ready to go and in production.

Looking forward, we envision supporting both the updated V25 as well as the totally new V3 preamp controller boards for several years into the future.

More info on the V25 will be forthcoming soon.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: craig sawyers on 20 Jan 2017, 04:32 pm
Looking good, Morten!

Will the IO3LDR be backward-compatible with the V2.1?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 20 Jan 2017, 08:13 pm
Will the IO3LDR be backward-compatible with the V2.1?

Yes but with a couple of qualifiers.

1) The default DIY V2.1 board has 3 NPN mosfet switches installed which would switch the original IO3 board  relays to ground. The new IO3LDR board now has the NPN mosfet switches instead. So you would have to snip the heads off the 3 mosfets on the V2.1 board and solder 2 of the remaining pins together on each of the 3 locations. As a result the IO3LDR boards just receives the TTL on/off (+V / 0V)  signal from controller board's microcontroller. Probably sounds more complicated than it really is. I will put together a simple diagram/photo and add to online documentation showing this.

2) The 3 terminal connectors J1L and J1R line up with each as before but on J1R the position of the input/output signals are reversed. A simple flip around of wiring takes care of that. The downside is you can't connect the IO3LDR to the V2.1 using straight across header pins. You need to use flexible wiring.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: craig sawyers on 20 Jan 2017, 11:33 pm
That sounds entirely doable - thanks Morten!

Once the boards are available, I'll be in line for two for my DIY balanced set up, which continues to delight!

Cheers

Craig
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: Ric Schultz on 21 Jan 2017, 01:44 am
Have you done straight wire bypass tests on the THAT goodie?  This is just an op amp.  Why would it sound better than other op amps with tons of feedback?  Hey, I am open to everything.  If it is the first opamp to pass straight wire testing then so be it.  I have used the OPA1632 (super low distortion balanced op amp...quickly looking at the specs they seem way better than THAT) to good effect......however, still sounds like an op amp (a bunch of bipolar transistors with a bunch of feedback).  Hey, it sounds really good.  Just not perfect.  I want perfect.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 21 Jan 2017, 06:10 am
Have you done straight wire bypass tests on the THAT goodie?  This is just an op amp.  Why would it sound better than other op amps with tons of feedback?  Hey, I am open to everything.  If it is the first opamp to pass straight wire testing then so be it.  I have used the OPA1632 (super low distortion balanced op amp...quickly looking at the specs they seem way better than THAT) to good effect......however, still sounds like an op amp (a bunch of bipolar transistors with a bunch of feedback).  Hey, it sounds really good.  Just not perfect.  I want perfect.

No, have not tested it in any way. But the point of my comment was not to suggest that THAT had the best IC/op-amp balanced line driver although it's something they do specialize in. My point was that there are IC alternatives to transformers that have comparable performance. Or (to avoid arguing about this)...good enough performance to satisfy my own personal metrics for diminishing returns which I fully concede may fall short of other folks' definition of perfect.

BTW, my understanding of the OPA1632 is that it's appropriate for balanced audio or to convert SE into balanced. The THAT IC line I meant to refer to is their 1200 series which are balanced input/receiver ICs that convert balanced signals back into SE and which are typically found used inside of some balanced amplifiers. THAT also makes the 1600 series output ICs for which OPA1632 would be a suitable alternative.

The only application of these that are potentially relevant to Tortuga Audio's products would be in converting SE to balanced within one of our preamps  that handles both SE and balanced inputs/outputs where we would convert the SE to balanced before attenuation so that the resulting output could be available both on as a SE output and a balanced output. The cleanest approach is to not mix signal types at all.

__________

addendum:  This pic from a THAT datasheet illustrates using a superior balanced input signal converter that's immune to differential source impedance imbalance. Again, this imbalance is what the OP was addressing.

 (http://www.audiocircle.com/image.php?id=156678)

 
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: craig sawyers on 22 Jan 2017, 07:22 pm
I think that it is interesting that the THAT balanced line receiver was developed by Bill Whitlock, one of the key technical people at Jensen Transformers and a pro-audio heavy hitter

http://www.jensen-transformers.com/history/

Craig
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 23 Jan 2017, 01:53 pm
I think that it is interesting that the THAT balanced line receiver was developed by Bill Whitlock, one of the key technical people at Jensen Transformers and a pro-audio heavy hitter

http://www.jensen-transformers.com/history/ (http://www.jensen-transformers.com/history/)

Craig

I've spoken with Bill Whitlock on occasion regarding Jensen's transformers and their applications. A truly bright light in the audio hardware world. Did not know he was behind THAT's line receiver IC but that's a strong endorsement of THAT's IC product line...in my view.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: craig sawyers on 23 Jan 2017, 07:14 pm
From http://www.thatcorp.com/press28.shtml

"THAT’s InGenius line receivers use technology developed and patented by Bill Whitlock, President of Jensen Transformers. He explained, "My design is almost completely insensitive to the source impedance imbalances which overwhelm typical balanced input stages. InGenius line receivers act like a transformer to present an extremely high input impedance to common mode (noise) signals. Even with a 600 ohm source-impedance imbalance, the InGenius topology delivers 70 dB typical common mode rejection. No other solid-state input stage can deliver that performance!"
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 3 Feb 2017, 05:51 pm
The further evolution of the V25. As we were getting closer to finalizing the  V25 design, I kept comparing the V25 to the V30 back and forth and soon realized there was no reason not to make the V25 be a variant on the V30 design. Unlike the V30 which will have a controller board/display board and one or more separate LDR/IO boards, the V25 has now morphed into a stand-alone version of the V30 minus certain features that I won't list here.

So here's an updated pic of the V25 board which now sports integrated 6 input switching plus a mono switch. This means no separate LDR IO board for the V25 although we already have those done already and may offer those to folks who are looking for an LDR based input switching board.  The V25 will drive the same  dual 7 segment displays as the current V2 board.

The V24 is 2.7" by 5.5" in size.

(http://www.tortugaaudio.com/images/LDRV25_integrated.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 3 Feb 2017, 06:19 pm
Interesting adding the input terminals to the main board. Will there be some savings over having two accessory boards.

Are those solder pads for each of the inputs and outputs? Only 6 ground solder pads? Looks like there will also be screw connectors for each input and output also.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 3 Feb 2017, 06:57 pm
Interesting adding the input terminals to the main board. Will there be some savings over having two accessory boards.

Are those solder pads for each of the inputs and outputs? Only 6 ground solder pads? Looks like there will also be screw connectors for each input and output also.


Cost savings was not the primary consideration although fewer parts and interface points tend to be more economical. The primary goal is sonic performance. Minimizing signal path length, complexity and interface points are all positives.

No screw connectors. Solder pads only. 6 possible stereo inputs. Signal grounds are kept separate for each channel with 3 solder pads per ground channel. Two output solder pads per channel. Inputs and output all switched via LDR modules. No relays in signal path. Board does have 2 small SPST relays associated with the LDR calibration circuit but these are not in the normal signal path.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 3 Feb 2017, 07:48 pm
Looks cool. Has what I am looking for.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: rajacat on 3 Feb 2017, 10:24 pm
Yes but with a couple of qualifiers.

1) The default DIY V2.1 board has 3 NPN mosfet switches installed which would switch the original IO3 board  relays to ground. The new IO3LDR board now has the NPN mosfet switches instead. So you would have to snip the heads off the 3 mosfets on the V2.1 board and solder 2 of the remaining pins together on each of the 3 locations. As a result the IO3LDR boards just receives the TTL on/off (+V / 0V)  signal from controller board's microcontroller. Probably sounds more complicated than it really is. I will put together a simple diagram/photo and add to online documentation showing this.

2) The 3 terminal connectors J1L and J1R line up with each as before but on J1R the position of the input/output signals are reversed. A simple flip around of wiring takes care of that. The downside is you can't connect the IO3LDR to the V2.1 using straight across header pins. You need to use flexible wiring.

Hi Morten,
I'm interested in the new IO3 LDR board if it's compatible with the LDR3x Rev 2.F controller board.

Thanks,

Roy
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: craig sawyers on 4 Feb 2017, 11:33 am
This means no separate LDR IO board for the V25 although we already have those done already and may offer those to folks who are looking for an LDR based input switching board.

Phew - that is a relief! I'm still absolutely in for two LDR I/O boards to upgrade my DIY balanced.

Craig
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 6 Feb 2017, 02:54 pm
Morten,

Looks like with the new board we go from 4 LDRs to a maximum of 15 LDRs, if using all six inputs and the mono option. In its use as an input switcher what is the lifespan of the LDR. Replacing all the modules could get rather pricey. For the DIY board, have you determined how you are going to price the unit based on the number of inlets? As a base board or as a base board with 3 inputs or as a base board with 6 inputs? Based on the selling price of the replacement modules, each input would add approximately $38 to the cost.

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 6 Feb 2017, 03:59 pm
Morten,

Looks like with the new board we go from 4 LDRs to a maximum of 15 LDRs, if using all six inputs and the mono option. In its use as an input switcher what is the lifespan of the LDR. Replacing all the modules could get rather pricey. For the DIY board, have you determined how you are going to price the unit based on the number of inlets? As a base board or as a base board with 3 inputs or as a base board with 6 inputs? Based on the selling price of the replacement modules, each input would add approximately $38 to the cost.

All good questions.

As it stands now the base board will be capable of 6 inputs plus mono but will have the option of being purchased as 1 input, 3 input or 6 input with significantly discounted pricing on the incremental LDR modules when purchased initially as part of the board. If someone wants to add more inputs later, then it's regular a la carte module pricing.  Final pricing will be set when we announce the release date.

Regarding the LDR lifespan question think of them as LED's which are considered to have 50,000 hour useful life when operated at their rated current capacity. We don't run the LDRs at their rated current capacity. While we do see LDRs go bad now and then it's still fairly rare and by "going bad" this usually means they drift out of calibration range for use as a variable resistor in our attenuator but they would still likely be perfectly acceptable to be used as on/off LDR switches. 

I've yet to have a single LDR fail when used as a simple on/off switch and we've been using LDRs as switches in practically every preamp we've sold going back to day 1.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 9 Feb 2017, 06:37 pm
The LDR.V25 preamp controller is now available for pre-order with an anticipated release date of April 1st.

Details on the V25 including pricing/options etc. can be found here: http://www.tortugaaudio.com/products/diy-preamp-components/ldr-v25-preamp-controller/ (http://www.tortugaaudio.com/products/diy-preamp-components/ldr-v25-preamp-controller/)

During the pre-release period we are offering the V25 at $50 off the list price.

If you wish to pre-order a V25 keep in mind that you will NOT be charged until the V25 is released.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 9 Feb 2017, 07:00 pm
Can we also use the Newsletter discount?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 9 Feb 2017, 07:15 pm
Can we also use the Newsletter discount?

Fair question. Given that the V25 base price is already marked down 17% during the pre-release/pre-order period the 10% newsletter discount is not applicable. It will be applicable once the board is released and the pre-release sales price expires.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 5 Mar 2017, 09:40 pm
Here's a fairly detailed pic of the V25 board with everything installed except the actual LDRs. This may be the final hardware version. Will know in a few days after we check it this latest build.

The V25 will likely end up using 12 DAC channels and 4 ADC channels compared to only 4 DAC channels in the V21 board. The additional DAC channels allow for more granular control of each of the 4 LDRs and a more accurate LDR calibration process.

(http://www.tortugaaudio.com/images/LDRV25_TopView_Horiz_1.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 18 Mar 2017, 02:37 pm
Hi Morten!

Will the V25 also be available as a Balanced Passive Preamp Kit for pre-order? If not, are the necessary cables (like master to slave ribbon cable) for balanced configuration going to be available among the DIY components?

/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 18 Mar 2017, 02:58 pm
Hi Morten!

Will the V25 also be available as a Balanced Passive Preamp Kit for pre-order? If not, are the necessary cables (like master to slave ribbon cable) for balanced configuration going to be available among the DIY components?

/ Simon

Hi Simon,

When anyone orders 2 V25 boards at the same time the assumption is these will be used for balanced and/or dual mono in which case we'll supply the additional shunt(jumper) on one board to designate it as the slave board and also the 12" 2-wire serial link (not a ribbon cable).

If someone already has a V25 and wants to buy a 2nd one for a balanced/dual-mono setup, just drop us a note and we'll add the shunt/serial link with that board. Those additional items literally cost us less than a $1.00 so I'm not inclined to add them as separate product line items with markup etc.

Also, just to be clear, any board can be designated as the master (no jumper) or slave (jumper installed). They're both identical in terms of hardware and firmware. The jumper determines their behavior.

Best,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 18 Mar 2017, 03:18 pm
Thank you!

I'm thinking about ordering two boards and one component kit but I'm also considering a Balanced Passive Preamp Kit with enclosure and everything to save some time and effort. Is the kit going to be available when the V25 is out?

/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 18 Mar 2017, 05:37 pm
Thank you!

I'm thinking about ordering two boards and one component kit but I'm also considering a Balanced Passive Preamp Kit with enclosure and everything to save some time and effort. Is the kit going to be available when the V25 is out?

/ Simon

A timely question. A somewhat involved answer.

The existing LDR1B.V2 kit uses a pair of existing V2 boards. One of the PITA aspects of the existing V2 boards is that firmware updates have to be made separately to each board. The plan with the V25 boards is you will only have to update the master board and it will take care of updating any attached slave boards. This way you will only need  a single USB connection in the enclosure connected to just the master board.

However, the initial firmware for the V25 will NOT have this ability - yet. Some more work/testing needs to be done before this feature is ready for prime time. What this means is you can buy and use V25 boards from the very beginning and use them in balanced/dual-mono scenarios but any firmware update will still have to be done to each board separately. A subsequent V25 firmware update will add the master>slave firmware update ability. Don't ask how soon this will be available. As fast as we can get it done is the only answer I have right now. To be clear, the hardware is fully capable of this, it's just a matter of working out the kinks in the firmware. Consequently, we will NOT be offering the updated LDR1B.V25 kits initially because all the new rear panels for the balanced V25 enclosure, including the kits, only have a single USB port so we won't release those models/enclosure/panel until the master>slave firmware updating is up and running. Hopefully that all makes sense.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 19 Mar 2017, 06:47 pm
Thanks for a very good and informative reply!

That all makes very much sense to me! It's just that I'm really bad at waiting and I have already pushed my limits to the max waiting for the V25 :) so I put two pre-orders (one V25 and one V25 with the component kit) and one order with an extra USB-cable and a PSU. I'm going to start with double USB-cables and then we see...

I'm really looking forward now :D
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: MadKid on 26 Mar 2017, 02:03 pm
Hi Morten,

Will V25 support LCD or OLED as a more fancy display option? Or will it be a major difference between V25 and V3?


Cheers,

Ken
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 26 Mar 2017, 02:40 pm
Hi Morten,

Will V25 support LCD or OLED as a more fancy display option? Or will it be a major difference between V25 and V3?


Cheers,

Ken

Timely question since I'm sorting out the details on this right now.

First, the V25 will remain compatible with our existing 7-segment type display modules.  This means it will work with our existing displays from day 1 and you can drop a V25 board into any preamp that currently uses our V20/V21 boards, plug in the existing displays and go.

However, the plan is to have the V25 also work with an OLED display that uses 2 rows of 16 alphanumeric characters. This new OLED display, while different than the graphical type OLED originally planned for the V30, will plug right into the same 2x5 pin header port used by our existing display modules. That serial port doesn't have the bandwidth to support the graphical OLED display but it's fine for a character OLED display.

By setting a jumper on the V25 you'll be able to use either display type. You won't need different firmware versions, just change a jumper setting.

The only wrinkle in this is that the V25's firmware will not be ready for the OLED character display from day 1.  When ready, a firmware update will enable the V25 to work with the new OLED display. I'm not going to make any promises on timing but best guess is somewhere in the 1-3 months time frame after original release of V25. It's a big priority to get this done.

Without a doubt, the new OLED character display will make using the V25 a lot simpler, more intuitive, and will make it possible to add or enhance features that are not practical with the existing dual 2-digit display/remote.

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 27 Mar 2017, 02:24 pm
I mentioned this in my last post but wanted to expand on it and let you all know what's happening with the V25.

The V25 will be released this week on April 1st as scheduled but will not begin shipping for another 2 weeks. I will extend the pre-order discount out through this period.

The reason for the delay is this past week I made a design change to the V25 that requires new printed circuit boards be made. That's going to take 7-10 days to turn around with our fabricator and then a few more days to build some boards and start shipping. Hence the April 15 ship date.

That's the bad news, now here's the good news.

The new V25 will now have an upgrade path to a much more user friendly and sophisticated OLED (organic light emitting diode) display panel. The OLED panel has 2 lines of 16 alphanumeric characters which will make control and menu navigation simpler and more intuitive, enable improvements to current features, and make it possible to add new features in the future that would otherwise not be practical. In order to make this possible I had to make some minor changes to the circuit board; hence the delay in shipping.

(This display window itself is 3.75"  wide by 1" tall.
A slightly smaller model is also available that has a 2.5" x 0.8" tall window.
We use an adapter board to be plug compatible with the V25 )

(http://www.tortugaaudio.com/images/oled_display_module.jpg)

When the V25 does ship it will work with our existing dual 2-digit 7-segment type display modules. That will not change. However, some additional software work needs to be completed for the OLED display upgrade. This will take a few more weeks and when ready we will roll out a simple firmware update that will then allow your V25 to work with the optional OLED display as well as continue to work with the existing dual display modules. Changing displays will be plug-n-play except you'll need to change a jumper on the V25 board. Either display type plugs into the same 10 pin header.

Nobody likes delays but I thought this one was worth making now since it required only minor changes to the hardware that I'd rather make now and not change the hardware a few weeks later leaving customers with incompatible boards.

Oh, and the V25 board sounds fantastic!!  I do believe it beats the existing V21 board sonically. The central reason for this is the way quieter power supply design on the V25 board which has 2 stage voltage regulation for the control signals to the LDRs.

Cheers,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: MadKid on 28 Mar 2017, 12:15 pm
That seems very promising and definitely the feature every builders are wanting for!

Guess I will place order for 2 boards for my balanced active preamp and upgrade later with the OLED display.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 Mar 2017, 02:28 pm
In addition to adding the OLED character display to the V25 we've also just added optional WiFi connectivity!

In many respects the V25 has slowly morphed into a variant of what we'd planned for the V3 only with a different architecture. In fact, the V3, at least as originally conceived, may now be moot.

The circuit board hardware for both WiFi and OLED display will be part of the V25 from day one. However, both will require additional software development before these optional feature are functional but this can be done with a simple firmware update via USB connection.

Once enabled, WiFi will make it possible for subsequent firmware updates to happen automatically in the background without any intervention. WiFi will also make it possible to control the V25 via a smartphone. This will require either a custom smartphone app to work. No promises on when that will be available but at least now it's a baked in upgrade path for the controller.

Cheers,
Morten

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 28 Mar 2017, 04:21 pm
I guess the main difference is that the V25 is limited to 2-channel, while the V3 could be used for multichannel. If the V3 would be mainly for multi-channel, each of the sub boards would not need the capability of 6 inputs and 2 outputs.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 Mar 2017, 05:41 pm
I guess the main difference is that the V25 is limited to 2-channel, while the V3 could be used for multichannel. If the V3 would be mainly for multi-channel, each of the sub boards would not need the capability of 6 inputs and 2 outputs.

A few points to help clarify this:

1) Each V25 board is a 2 channel board  same as each V3 LDR board was going to be a 2 channel board.

2) Each V25 board can switch up to 6 different 2 channel sources....the same as the V3 LDR was going to do.

3) Multiple V25 boards can be daisy chained together in a multi-channel configuration same as the V3 was going to do. The simplest example of this is dual boards for a balanced audio setup.

4) It's true that for true multi-channel applications each 2 channel board does not need the ability to switch between multiple input sources. This is true of the V25 and would have been equally true for the V3. To the extent that there's demand for multi-channel applications of the V25, a variant of the V25 could be produced that only accommodates a single source. This would reduce the physical size of that V25 variant board between 35-50%.

As I thought through these points the key difference between the V25 and the V3 is that the V3 was conceived to have only a single processor on a separate control board linked to 1 or more "dumb" LDR I/O boards. The V25 approach puts a processor on every board and there's only one type of board. The first V25 board becomes the master and all the other V25 boards connected to it via a daisy chain of serial data links becomes a slave board (by setting a jumper).

When I started down the road  on the V25 it was supposed to be simpler and less capable than the V3 and yet still be a logical step up from the existing V2. Instead it has morphed into its own variation on the V3 mainly because I couldn't come up with a good reason not to. Initially, some features inherent in the V25 will not be available until a later date when the software catches up with the hardware.

Cheers,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 28 Mar 2017, 08:13 pm
So hypothetically, if I would like to do 6 channels on input #1 of the boards, and have 2-channel sources for inputs #2 and #3. I could add 3 boards: 2 with single input LDR and one with 3 input LDRs. So only the Main board would have the three inputs? (I realize that all the boards have 6 inputs and 2 outputs, but adding additional LDRs does cost more.)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 Mar 2017, 08:32 pm
So hypothetically, if I would like to do 6 channels on input #1 of the boards, and have 2-channel sources for inputs #2 and #3. I could add 3 boards: 2 with single input LDR and one with 3 input LDRs. So only the Main board would have the three inputs? (I realize that all the boards have 6 inputs and 2 outputs, but adding additional LDRs does cost more.)

If I'm following you then  it would look something like below.  I'm curious if this is just a theoretical scenario, or if not, what kind of setup would have these characteristics ?

Board #1 (2 channels) - single source - LDRs on input #1 only

Board #2 (2 channels) - 2 sources - LDRs on inputs #1 and #2 only

Board #3 (2 channels) - 2 sources - LDRs on inputs #1 and #2 only

You'd have 6 total channels. You would designate board #1 as the master and #2 and #3 as the slave. Display and control interfaces with master board only. When volume raised/lowered on #1 master the other 2 boards follow in lock step.

One of the wrinkles that would need to get ironed out with software is how to handle input switching between master and slave boards since they all don't have the same # of input sources. I'm sure this can get worked out during the board setup process.

One clarification: the V25 has up to 6 switchable inputs but it does not have 2 switchable outputs. There is only 1 output per board (1 output per channel).

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 29 Mar 2017, 02:52 am
Not quite what I was thinking.

Board #1 - Master Board - 3 inputs (#1 multi-channel (2 Channels), #2 and #3 2-channel (2 channels))
Board #2 - Slave Board - 1 input (#1 multi channel) (2 Channels)
Board #3 - Slave Board - 1 input (#1 multi-channel) (2 Channels)

Input #1 is my DVD-Audio player (5.1 analog), Input #2 is a DAC, Input #3 is a Phono. So, if I switch to input #1 it will play in all 6 channels, but if I switch to input #2 it will only play in 2 channels?

So, as I understand it each board has a single output (Left and Right for 2 channels of output).
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 29 Mar 2017, 02:32 pm
Not quite what I was thinking.

Board #1 - Master Board - 3 inputs (#1 multi-channel (2 Channels), #2 and #3 2-channel (2 channels))
Board #2 - Slave Board - 1 input (#1 multi channel) (2 Channels)
Board #3 - Slave Board - 1 input (#1 multi-channel) (2 Channels)

Input #1 is my DVD-Audio player (5.1 analog), Input #2 is a DAC, Input #3 is a Phono. So, if I switch to input #1 it will play in all 6 channels, but if I switch to input #2 it will only play in 2 channels?

So, as I understand it each board has a single output (Left and Right for 2 channels of output).

Right then. See no reason why that won't work. A detail that has to be thought through is what do the slaves board do when the master switches to #2 or #3 input. The simplest approach is the slaves act normally and do the same as the master by switching to inputs #2 or #3 that connect to nothing so who cares. A more deliberate approach is to makes the slave boards know they only have 1 input so when master asks for #2 or #3 the slaves shut off #1 and shut off their output as well. This can all be worked out through software and a setup menu.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 29 Mar 2017, 02:55 pm
The V25 is now fully cooked and production boards have been ordered.  :thumb:

As I was finalizing the layout I took another look at the OLED 2x16 character display and decided I wasn't totally thrilled with the look of that display compared to the fully graphic OLED display I'd been using for the V3 board. After some late night editing I was able to add an optional 14 pin header that will allow the V25 to use the graphic OLED display. It still retains the potential of using a character based OLED display but I suspect I'll end up focusing on the graphical version. The programming for the graphic display is way more complicated, uses way more memory and requires a fast processor but the V25 has the horsepower and capacity plus most of the really hard graphic infrastructure programming is already done. To make room for the new 14 pin header, I changed the USB port from a simple 5 pin header to a vertical mounted micro USB type B socket which has a much smaller footprint.

Thus, the first production V25 board will now have the option (in terms of hardware) of driving a 7 segment display (our current display modules), a character based OLED display, or a higher resolution graphic OLED display. It also has the option of plugging in a WiFi module.

Final changes included a larger linear regulator to handle the added WiFi and display options. Also added an optional input/output pin header for direct connecting to  I/O jack boards.

The final board size grew 0.2 inches in length to 5.7 inches wide by 2.7 inches tall.

 That's it. Done and done. We'll have V25 boards in house in 2 weeks (or less) at which point we expect to begin shipping.

Cheers,
Morten

(http://www.tortugaaudio.com/images/LDRV25_Final_PCB_CAD_RevA3.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mrvco on 2 Apr 2017, 03:58 pm
Morton - Looks great, any idea yet on when the v25 boards will be available in production LDR3 preamps?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 2 Apr 2017, 05:07 pm
Morton - Looks great, any idea yet on when the v25 boards will be available in production LDR3 preamps?

Blank production boards are scheduled to arrive in-house by April 10. We'll need a few days to build and commission an initial lot which means we're on track to start shipping V25 boards by around April 15th. Later in April we'll be announcing new versions of our finished preamps based on the V25.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mikebarney on 5 Apr 2017, 12:07 pm
Morten-
Any chance the new display will have the capability to label inputs, such as "Phono", "Tuner" or "DAC", instead of simply 1,2 or 3?
Either user programmable or even pick from a pre-defined list would be great!
Thanks,
Mike

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 5 Apr 2017, 01:45 pm
Morten-
Any chance the new display will have the capability to label inputs, such as "Phono", "Tuner" or "DAC", instead of simply 1,2 or 3?
Either user programmable or even pick from a pre-defined list would be great!
Thanks,
Mike

Yes!
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mikebarney on 5 Apr 2017, 02:02 pm
Great!
Thanks,
Mike
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mrvco on 8 Apr 2017, 01:27 am
Blank production boards are scheduled to arrive in-house by April 10. We'll need a few days to build and commission an initial lot which means we're on track to start shipping V25 boards by around April 15th. Later in April we'll be announcing new versions of our finished preamps based on the V25.

Thanks, looking forward to it!
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: kernelbob on 8 Apr 2017, 01:23 pm
Hi Morten,
Personally, I'm quite happy with the Apple remote.  I don't have to go hunting to find the particular button to control a particular function.  Any chance that version 3 will continue to also support the Apple remote?

thanks, Robert
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 8 Apr 2017, 06:04 pm
Hi Morten,
Personally, I'm quite happy with the Apple remote.  I don't have to go hunting to find the particular button to control a particular function.  Any chance that version 3 will continue to also support the Apple remote?

thanks, Robert

I've no intention of abandoning the Apple remote after releasing the Tortuga remote. I can imagine there may come a day where certain features or functionality may be possible with Tortuga remote that may not be practical with Apple remote but I don't see that happening anytime soon. Plus, when the new menu based OLED display option becomes available for the V25 board that display will allow the Apple remote to handle most anything without having to remember modes and button sequences.  Both remotes use the same NEC IR protocol so the communications infrastructure hardware/software is the same for both even though they transmit different specific button codes.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 21 Apr 2017, 09:23 pm
Here it is at last, the first production board of the new LDR.V25 Preamp Controller.   :thumb:
The board in this pic has a full complement of LDRs installed except for the Mono switch.

(http://www.tortugaaudio.com/images/LDRV25_TopView_3.jpg)
(http://www.tortugaaudio.com/images/LDRV25_SideView_1.jpg)
(http://www.tortugaaudio.com/images/LDRV25_TopFrontView.jpg)
(http://www.tortugaaudio.com/images/LDRV25_TopRearView.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 24 Apr 2017, 07:20 pm
Looks superb! LDR for all preamp I/O and attenuation functions is looks to be a game changer and I'm really looking forward to integrating these into my system!

Adrian
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: doggie on 1 May 2017, 03:58 pm
Hi Morten,

I skimmed through the thread but did not see any mention of being able to replace the board in our existing units with this new one.

Is there an upgrade path for existing users either as DIY or through you?

Best,

Paul
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 1 May 2017, 05:22 pm
Hi Morten,

I skimmed through the thread but did not see any mention of being able to replace the board in our existing units with this new one.

Is there an upgrade path for existing users either as DIY or through you?

Best,

Paul

While I've yet to announce any upgrade program, the key points that come to mind in considering an upgrade from a V2 to a V25 are as listed below. I'm sure this list will evolve.

1) Both boards use the same Tortuga Audio display modules, encoder & IR receiver module
2) Both boards use the same Apple remote
3) Both boards can use the same power supply
4) The V25 is slightly wider and longer than the V2 so the mounting holes will be different.
5) The V25 has its own input switching so you'll no longer need your existing external switching board used with the V2
6) Both boards use the same 5 pin USB header connection except the header is on the underside of the V25 board
7) The V25 board has no piggy-back board on its underside so overall the V25 can be mounted lower than the V2.
8 ) With the V25 you MUST connect the IR receiver module to the master display module since there's no place to mount the IR receiver directly to the V25 board itself.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: robertopisa on 2 May 2017, 09:18 am
I stay tuned for the upgrade from v2.0, I have two boards for balanced configuration.

Cheers
Roberto

While I've yet to announce any upgrade program, the key points that come to mind in considering an upgrade from a V2 to a V25 are as listed below. I'm sure this list will evolve.

1) Both boards use the same Tortuga Audio display modules, encoder & IR receiver module
2) Both boards use the same Apple remote
3) Both boards can use the same power supply
4) The V25 is slightly wider and longer than the V2 so the mounting holes will be different.
5) The V25 has its own input switching so you'll no longer need your existing external switching board used with the V2
6) Both boards use the same 5 pin USB header connection except the header is on the underside of the V25 board
7) The V25 board has no piggy-back board on its underside so overall the V25 can be mounted lower than the V2.
8 ) With the V25 you MUST connect the IR receiver module to the master display module since there's no place to mount the IR receiver directly to the V25 board itself.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 10 May 2017, 10:11 pm
Morten,

Will there be the option on the V25 to supply your own regulated +5v (I have a Belleson reg based PSU I'd like to use).
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 11 May 2017, 01:28 pm
Morten,

Will there be the option on the V25 to supply your own regulated +5v (I have a Belleson reg based PSU I'd like to use).

There's no deliberate option to bring in an external source of 5 V. That said, you could achieve this by removing the U11 5V regulator entirely and connecting a +5V and Gnd at the solder pads. The existing regulator uses the 7805 pin out although it's not a 7805.

Before going down that road it's worth reviewing the power supply arrangement and asking yourself if this is really worth it.

First, the existing U11 5V regulator is a high performance low noise switching regulator that's essentially a 7805 drop-in replacement. Second, the 5V supply is not directly used to power the primary LDRs although it is used to power the on/off LDRs used for input switching. Lastly, the 5V is further regulated down to 3.3V via a low noise low dropout linear regulator. The 3.3V  power is used to power the processor and to regulate the LDRs used for volume control.

In my view, the V25 is unlikely to benefit from being powered directly from an external 5 V source. I can't prove that. It's simply an engineering judgement. I've been wrong before about the impact of power supply quality on the V2 board design but the V25 is quite different from the V2. With the V2 the incoming power source is used directly (no filtering/conditioning etc.) to power the 2 op amp chips that are part of the LDR control circuit. With the V25 there's 2 stages of voltage regulation (SMPS followed by linear) upstream of the control op amps.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 11 May 2017, 02:16 pm
One aspect of the V25 design that I've probably not mentioned before is that unlike the V2 design which maintains minimal power on some LDRs even when "turned off",  in the V25 all the LDRs are 100% powered down when the unit is turned off. Hard to quantify the long terms benefits other than to say it will arguably extend the useful life of the LDRs just that much longer.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 11 May 2017, 05:46 pm
Agreed, too complex and not worth it. Generally (well 99.99% of the time) I'd rather go with the engineered solution by the designer, just wanted to see if there was a straightforward option with +5v that met the prior statement.
Thanks!
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mlundy57 on 11 May 2017, 07:09 pm
Will the V3 have an HT by-pass feature?

I use my main speakers for both music and HT. For music I have three inputs the DAC connected to my music server for digital files, the 2 channel output from an OPPO 105 for SACD & DVD-A, and my turntable. The AVR handles movies.

Without an HT by-pass I have to use two different sets of speaker cables and a pair of dummy loads with the main speakers and switch back and forth for music or movies.

With an HT by-pass (that feeds both outputs since my speakers are bi-amped) the AVR's main pre-outs would be connected to the HT by-pass input which would eliminate the need for the second pair of speaker cables, the dummy loads and the need to switch back and forth.

Mike
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 12 May 2017, 01:01 pm
Will the V3 have an HT by-pass feature?

I use my main speakers for both music and HT. For music I have three inputs the DAC connected to my music server for digital files, the 2 channel output from an OPPO 105 for SACD & DVD-A, and my turntable. The AVR handles movies.

Without an HT by-pass I have to use two different sets of speaker cables and a pair of dummy loads with the main speakers and switch back and forth for music or movies.

With an HT by-pass (that feeds both outputs since my speakers are bi-amped) the AVR's main pre-outs would be connected to the HT by-pass input which would eliminate the need for the second pair of speaker cables, the dummy loads and the need to switch back and forth.

Mike


Before I answer your specific question, I want to clarify that our recently released V25 has effectively displaced the V3 which is no longer being developed.


The V25 doesn't have a specific HT bypass feature. That said, there's a very straightforward way to use the V25 in a bypass mode. Attach your HT to one of the V25 inputs and when that input is selected raise the V25 volume to 100%. At that point use your HT to control volume. While not a true physical bypass it accomplishes the same outcome. No worries when you switch the V25 back to some other input because it automatically cuts the volume level back to a default max level of 50%.

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mlundy57 on 12 May 2017, 04:18 pm

Before I answer your specific question, I want to clarify that our recently released V25 has effectively displaced the V3 which is no longer being developed.


The V25 doesn't have a specific HT bypass feature. That said, there's a very straightforward way to use the V25 in a bypass mode. Attach your HT to one of the V25 inputs and when that input is selected raise the V25 volume to 100%. At that point use your HT to control volume. While not a true physical bypass it accomplishes the same outcome. No worries when you switch the V25 back to some other input because it automatically cuts the volume level back to a default max level of 50%.

For that to work in my system without having to go back to swapping out two pairs of speaker cables when I switch from listening to music to watching movies, the V25 would have to have four inputs instead of three: (1) OPPO 105's 2 channel analog outputs, (2) the file server's DAC, (3) the phono pre-amp, and (4) the AVR for movies and multi-channel music.

While I used to do this since my preamp only had three inputs, now that I have a pre with the HT by-pass/4th input and no longer have to swap out speaker cables I've become spoiled and don't want to go back.

Maybe something to keep in mind for a future upgrade.

Thanks

Mike
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 12 May 2017, 04:42 pm
For that to work in my system without having to go back to swapping out two pairs of speaker cables when I switch from listening to music to watching movies, the V25 would have to have four inputs instead of three: (1) OPPO 105's 2 channel analog outputs, (2) the file server's DAC, (3) the phono pre-amp, and (4) the AVR for movies and multi-channel music.

While I used to do this since my preamp only had three inputs, now that I have a pre with the HT by-pass/4th input and no longer have to swap out speaker cables I've become spoiled and don't want to go back.

Maybe something to keep in mind for a future upgrade.

Thanks

Mike

Hi Mike,

Sorry the misunderstanding but the V25 can accommodate up to 6 stereo inputs directly on the board - no additional external input switching hardware required. Any one of those 6 could be your AVR input. If you only need 4 inputs no problem. When the 4th input (your AVR) is selected just run the volume up to 100% - instant HT bypass (effectively).

Best,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mlundy57 on 12 May 2017, 04:55 pm
Hi Mike,

Sorry the misunderstanding but the V25 can accommodate up to 6 stereo inputs directly on the board - no additional external input switching hardware required. Any one of those 6 could be your AVR input. If you only need 4 inputs no problem. When the 4th input (your AVR) is selected just run the volume up to 100% - instant HT bypass (effectively).

Best,
Morten

You have my attention.

What's the status of the V25?

Mike
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 12 May 2017, 05:57 pm
You have my attention.

What's the status of the V25?

Mike

The V25 has been released but we are roughly 2-3 weeks behind in shipments. Putting a huge effort into optimizing the auto-calibration algorithm which has slowed shipments to a crawl. Expect to break the logjam any day now. The V25 has a way more sophisticated control scheme compared to the V2 so adapting the V2's algorithm to the V25 has taken much longer than planned.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: mlundy57 on 12 May 2017, 06:01 pm
Thanks

I just finished reading the V25 thread so I'll be following that one

Mike
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 12 May 2017, 06:15 pm
Thanks

I just finished reading the V25 thread so I'll be following that one

Mike

I've merged both topics into the V25 thread since they were so closely related.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 31 May 2017, 07:50 pm
So can a pair of boards running as a balanced pair be combined with boards running single ended in a multi-channel application?

The first two boards will run the front right and left speakers balanced. My center and surrounds will be single ended or unbalanced. So that would be another two boards running single ended. Is this possible with the board controller?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 31 May 2017, 08:14 pm
So can a pair of boards running as a balanced pair be combined with boards running single ended in a multi-channel application?

The first two boards will run the front right and left speakers balanced. My center and surrounds will be single ended or unbalanced. So that would be another two boards running single ended. Is this possible with the board controller?

Multiple V25 boards can be daisy-chained together with one ultimate master board. The first slave connected to the master passes on all commands to the next slave and so on. Communications between each board is currently one-way (master->slave1->slave2 etc. ) via serial UART protocol. Eventually we will add 2 way comm so slaves can send data upstream to the master.

Each V25 can handle 2 channels. Hence for stereo balanced you need 2 boards for 4 total channels (2 right channels & 2 left channels). Add up all the channels you want to control and divide by 2 and round up to get the number of V25 boards needed. For 5 channels 5/2 = 2.5 or 3 V25 boards.

Also, something I haven't broadcast is that any computer, arduino, raspberry PI etc. equipped with a UART (very common serial comm) could act as a master to control 1 or more V25 boards.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 1 Jun 2017, 08:58 pm
So how would another controller connect to the board? Terminal pins or USB? Learning about serial communications with my Soekris DAC build. Interesting thing to tinker with.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 2 Jun 2017, 02:05 pm
So how would another controller connect to the board? Terminal pins or USB? Learning about serial communications with my Soekris DAC build. Interesting thing to tinker with.

Via a connection to pin RX2 on header J7 -  a single wire serial data link. Using standard UART protocol at 115,000 baud, 8 bits, 1 stop bit, no parity. We haven't published the commands yet but will do so in the future and post this info in our online documentation.

Currently this is only one-way  external controller -> V25.J7.RX2.   Future V25 firmware will enable 2-way communication by adding a second serial wire connection via V25.J7.TX2 - > external controller.

 For those unfamiliar with UART (or USART) it's an old yet reliable serial data protocol going way back to analog telephone days and is closely related to RS232 et. al.  All Arduinos, microcontrollers, Raspberry PI's etc. have this built into their hardware. PCs used to all have RS232 before moving to USB which is way more complex  but faster and more flexible but there are cheap USB/UART interface adapter devices available for PCs and MACs.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 2 Jun 2017, 04:43 pm
So would your display either the 7 segment or the new OLED display still be required if we could use UART control?

I was thinking if I could install the LDR.V25 in my DAC/Raspberry Pi streamer and use one display that shows DAC and LDR settings such as inputs and volume control. Would have to interface with a UART controller on the pi, or an arduino due if the pi can't address multiple UART satisfactorily. I am assuming that the LDR.V25 and DAC will need different UART controllers since the command sets are different.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 2 Jun 2017, 04:56 pm
So would your display either the 7 segment or the new OLED display still be required if we could use UART control?

That would be up to you. The V25 would display normally to whatever display is attached. Or, you could handle all of that with your own display being driven by your arduino, PI etc.

Quote
I was thinking if I could install the LDR.V25 in my DAC/Raspberry Pi streamer and use one display that shows DAC and LDR settings such as inputs and volume control. Would have to interface with a UART controller on the pi, or an arduino due if the pi can't address multiple UART satisfactorily. I am assuming that the LDR.V25 and DAC will need different UART controllers since the command sets are different.

Generally speaking UART is not good for networking of multiple devices off a single UART pair. You would likely need a dedicated UART port for each device you're communicating with. In the case of the V25, daisy-chaining 2 or more boards together is done by using 2 separate UART ports per board instead of all the boards being on a single UART link.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: MadKid on 13 Jun 2017, 08:17 am
Hi Morten,

Well received the boards and waiting for the new enclosure.

I got two questions thou. Is there a reason to have the USB 5 pins header solder on back side of the board? I'm a little bit confused as it is riding over the solder pads of J9. Also what is the usage of the 10 pins header on the back side, right underneath the processor chip. It is not mentioned in documentation and it seems kind of bad soldered.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 13 Jun 2017, 11:41 am
Hi Morten,

Well received the boards and waiting for the new enclosure.

I got two questions thou. Is there a reason to have the USB 5 pins header solder on back side of the board? I'm a little bit confused as it is riding over the solder pads of J9. Also what is the usage of the 10 pins header on the back side, right underneath the processor chip. It is not mentioned in documentation and it seems kind of bad soldered.

The 90 degree J8 USB pin header is on the underside with a side entry to avoid interference other headers topside. With ribbon cables plugged into both J3 and J9 there's little or no room to connect to J8 topside. There's sufficient clearance from the J9 solder pads to not impede the functioning of J9 and if by chance the J8 is touching one of the J9 legs it's because it wasn't tilted down properly when installed in which case it's a simple matter to slightly bend the J8 pins down to clear J9.

The 10 pin connection on the underside is there solely to initially program the processor bootloader and is not used thereafter. Eventually we'll elimante this connector by pre-programming the chips before install. Firmware loading/updating is done via USB.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 17 Jun 2017, 11:21 pm
Hello Morten!

My enclosure from Hifi2000 arrived yesterday so I have been building almost nonstop since then on my balanced V25s. I have been trying to avoid all wiring mistakes and I have double checked everything before powering on. To my relief, no magic smoke, it powered up fine! :) It was good guidance in the support documentation!

However before testing, I would like to upgrade to the latest firmware. I have been trying soooo many times now without being able to connect. I've been following the instructions and I understand that 5 sec gap but still no success. I have tried both in Linux (running the bootloader in an emulator with full privileges) and also from a laptop with Windows 10 (both as standard user and administrator). It just keeps saying the same thing: "Unable to find device: USB HID Bootloader." I have tried both the Master and the Slave board.

Am I missing something?

Many thanks!
/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 18 Jun 2017, 11:50 am
Hello Morten!

My enclosure from Hifi2000 arrived yesterday so I have been building almost nonstop since then on my balanced V25s. I have been trying to avoid all wiring mistakes and I have double checked everything before powering on. To my relief, no magic smoke, it powered up fine! :) It was good guidance in the support documentation!

However before testing, I would like to upgrade to the latest firmware. I have been trying soooo many times now without being able to connect. I've been following the instructions and I understand that 5 sec gap but still no success. I have tried both in Linux (running the bootloader in an emulator with full privileges) and also from a laptop with Windows 10 (both as standard user and administrator). It just keeps saying the same thing: "Unable to find device: USB HID Bootloader." I have tried both the Master and the Slave board.

Am I missing something?

Many thanks!
/ Simon

Hi Simon,

First, be assured that the firmware bootloader process/system works flawlessly when set up and executed properly. I do this practically every day with our preamp boards. It's how the boards you have were programmed. It's worked fine for me under Windows7, 8 and now 10.

The #1 most likely reason you're having this problem is with the USB cable you are using. More and more USB cables today are really not data cables but are essentially 5V power charging cables for various digital devices like cell phones etc. I've not taken one of those cables apart to see for myself but apparently they lack one or both of the D+ and D- USB data lines.

Other customers have had this problem and after getting a proper USB cable the firmware bootloader worked as it should.

A way less likely cause is if you have a USB port monitoring program running on your PC that could be interfering. I've not run into this with our preamp boards but it's been reported by others using similar bootloader tools. One program cited was Advanced USB Port Monitor. After turning it off the USB monitor or removing it from their PC, the bootloader worked fine.

I suggest you try a different cable and see how it goes.

Best,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 18 Jun 2017, 05:07 pm
Thank you Morten!

I already suspected the cable might be the one causing problems because I've had previous bad experiences before. Since it was the cable from the kit I thought it was tested, plus that I didn't have any other USB-A male to male to try with. I just bought a really short (to be on the safe side) USB.3 cable and now it works!!  :D

Some other questions:
I think I read somewhere that the autocal is running in the background?
If I adjust the impedance it has to run through autocal to work, right?
I have tried to start it manually according to the info in the support pages but display stays off no matter what I try :(
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 18 Jun 2017, 05:22 pm
Haha, now I have f**ked it up completely. Now even the first "1   20" setting won't work any more, just some white noise.  :duh: :scratch:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 18 Jun 2017, 06:46 pm
Thank you Morten!

I already suspected the cable might be the one causing problems because I've had previous bad experiences before. Since it was the cable from the kit I thought it was tested, plus that I didn't have any other USB-A male to male to try with. I just bought a really short (to be on the safe side) USB.3 cable and now it works!!  :D

Glad to hear you got the firmware update working. So many USB cables theses days are just charging cables and not actual USB data cables.

Quote
Some other questions:
I think I read somewhere that the autocal is running in the background?

Not yet. That's something that will be introduced in a future version of the firmware. For now, you have to start it manually.

Quote
If I adjust the impedance it has to run through autocal to work, right?
I have tried to start it manually according to the info in the support pages but display stays off no matter what I try :(

Yes, after making changes to impedance setting number and/or level you have to rerun autocal for those changes to become effective.
If the displays stay off, you have not started autocal.

With the V25 it's a bit different than the V2. You first have to turn the unit on, then press the mode button 5 times to get it to autocal mode, then press the right button 3 times to start.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 18 Jun 2017, 06:52 pm
Haha, now I have f**ked it up completely. Now even the first "1   20" setting won't work any more, just some white noise.  :duh: :scratch:

With kits the #1 mistake people make is not properly grounding the audio signals. The left and right side signal grounds must both be connected to star ground point for autocal to work properly. You can't calibrate the LDRs without a reference to ground.

(https://www.tortugaaudio.com/images/V25_singleended_wiring_schematic.jpg)
(https://www.tortugaaudio.com/images/V25_singleended_wiring.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 18 Jun 2017, 08:53 pm
Thanks for a good and rapid reply!

Good that you updated the firmware section with some cable info. It's probably better not to send a cable with the kit than to get that bad one I got. 

I was wondering what that 5th control mode was with the two zeroes!!  :D

Star ground was already sorted. I must admit that at first, I did feel a little uncertain to connect the ground from the PSU though!
Problem solved, I had just missed that the autocal was working differently on the V25. I did try my best to seek the answer in the documentation but couldn't find any info about that 5th control mode... Thanks for clearing that up!  :thumb:
(seems like a better way to do it than the old way anyway.)

I got two pairs of XLR inputs and two pairs of XLR outputs and I thought that was minimalistic until I did the wiring. It was not that difficult, it's just a lot more cables than you first think!!
All the "1" to star ground (didn't daisy-chain), all "2" to Master, all "3" to Slave was really straight forward! Otherwise I would have had to mark the cables to not mess up. 
Anyway, I used the Neotech 26AWG solid copper cable you recommended, nice cable but if you are using short lengths it's easy that you'll just move the whole sheet when stripping them.

Autocal seems to be running fine now. I have managed to save 3 presets but when trying to save the 4th It just keeps erasing it. Do they have to be in rising order? (like 10, 20, 30, 40 instead of mixed?) Any other ideas?
I have been trying with a complete restart as well btw. It sometimes says "4   1" instead of "0   0" in the 5th control mode if that's any help.

The next few days I'm gonna be up for some serious listening!!  :D
/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 20 Jun 2017, 06:36 pm
It finishes autocal without any problems. It does say "4   1" in the fifth control mode afterward sometimes which I don't understand. First I thought it might not have finished the fourth check but I've been watching it and it seems to finish all checks just fine. It goes away after a restart/killing the power though and goes back to "0   0". Does this mean anything? A faulty LDR? A badly grounded cable?

Many thanks!
/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 20 Jun 2017, 07:45 pm
It finishes autocal without any problems. It does say "4   1" in the fifth control mode afterward sometimes which I don't understand. First I thought it might not have finished the fourth check but I've been watching it and it seems to finish all checks just fine. It goes away after a restart/killing the power though and goes back to "0   0". Does this mean anything? A faulty LDR? A badly grounded cable?

Many thanks!
/ Simon

No, that's "normal" but will be removed in next firmware build. It should reset to 0/0 but doesn't mean anything.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 26 Jun 2017, 07:35 pm
On the question of daisy chaining-

For a four v25 board configuration, would I go about daisy chaining the boards as (?) :

Master (tx1, rx1) -> Slave 1 (rx2, tx2)
Slave 1 (tx1, rx1) -> Slave 2 (rx2, tx2)
Slave 2 (tx1, rx1) -> Slave 3 (rx2, tx2)

Or would it more of a hub and spoke with a loop back connection from the last slave like:

Master (tx1) -> Slave 1 (rx2)
Master (tx1) -> Slave 2 (rx2)
Master (tx1, rx1) -> Slave 3 (rx2, tx2)

Or hub and spoke with loopback from each slave to the master like:

Master (tx1, rx1) -> Slave 1 (rx2, tx2)
Master (tx1, rx1) -> Salve 2 (rx2, tx2)
Master (tx1, rx1) -> Slave 3 (rx2, tx2)

This is with the latest FW. I would only be connecting DM1 master/slave module + encoder + ir rx to Master board.
The goal is to have the master handle volume and input selection control for 4 single ended stereo channels. For 2 inputs, I would populate every board with LDRs appropriately.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 27 Jun 2017, 02:13 am
On the question of daisy chaining-

For a four v25 board configuration, would I go about daisy chaining the boards as (?) :

Master (tx1, rx1) -> Slave 1 (rx2, tx2)
Slave 1 (tx1, rx1) -> Slave 2 (rx2, tx2)
Slave 2 (tx1, rx1) -> Slave 3 (rx2, tx2)

Or would it more of a hub and spoke with a loop back connection from the last slave like:

Master (tx1) -> Slave 1 (rx2)
Master (tx1) -> Slave 2 (rx2)
Master (tx1, rx1) -> Slave 3 (rx2, tx2)

Or hub and spoke with loopback from each slave to the master like:

Master (tx1, rx1) -> Slave 1 (rx2, tx2)
Master (tx1, rx1) -> Salve 2 (rx2, tx2)
Master (tx1, rx1) -> Slave 3 (rx2, tx2)

This is with the latest FW. I would only be connecting DM1 master/slave module + encoder + ir rx to Master board.
The goal is to have the master handle volume and input selection control for 4 single ended stereo channels. For 2 inputs, I would populate every board with LDRs appropriately.


This is the way to go with the multi-channel daisy-chain of V25 boards.

Master (tx1, rx1) -> Slave 1 (rx2, tx2)
Slave 1 (tx1, rx1) -> Slave 2 (rx2, tx2)
Slave 2 (tx1, rx1) -> Slave 3 (rx2, tx2)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 28 Jun 2017, 07:26 pm
Thanks Morten- looking forward to getting the multichannel LDR passive going!  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 Jun 2017, 08:40 pm
Thanks Morten- looking forward to getting the multichannel LDR passive going!  :thumb:


New boards on their way. I expect you'll have them for the weekend.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 6 Jul 2017, 07:00 pm
Hey Morten,

How do you go about switching absolute polarity/phase with v25 in a balanced config?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 6 Jul 2017, 07:08 pm
Hey Morten,

How do you go about switching absolute polarity/phase with v25 in a balanced config?


You would dedicate 2 inputs to the same balanced signal but swap the phases when wiring up the second input. You would then fast-switch the input between the 2. If you used say inputs #4 and 5 you'd switch back and forth between them while listening to music to discern which sounds better.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: enser on 6 Jul 2017, 08:54 pm
Ah yes, that will work well. Thanks again- the balanced v25s sound great btw.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 7 Jul 2017, 02:01 am
Morten,

With a balanced build with 2 boards, can you have some inputs balanced and some unbalanced? There was a comment in the v25 specifications on the website that seemed to imply that the balanced and unbalanced inputs could be combined with a two board build. I could see how it would work on the inputs, but I was kind of curious how that would work with the outputs. Would you be able to have only balanced outputs?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 7 Jul 2017, 01:25 pm
Morten,

With a balanced build with 2 boards, can you have some inputs balanced and some unbalanced? There was a comment in the v25 specifications on the website that seemed to imply that the balanced and unbalanced inputs could be combined with a two board build. I could see how it would work on the inputs, but I was kind of curious how that would work with the outputs. Would you be able to have only balanced outputs?

Yes, with dual boards you can mix balanced and single-ended inputs.

It gets a bit messy to explain/show but with balanced signals the master board handles the + phase for both the right/left channels and similarly the slave board handles the - phase for both channels. This arrangement is necessary in order for the channel balance adjustment feature to work properly.

To add single-ended inputs you would would only connect inputs to the master board's right/left channels.

The output wiring follows the same approach as the inputs. When a balanced input is selected that attenuated signal would also be present on the RCA output jacks but only from a single phase so the volume would be reduced. When a single-ended input is selected the balanced output would have a signal present on only one phase.

V25 Balanced Wiring
(https://www.tortugaaudio.com/images/V25_balanced_wiring.jpg)

V25 Single-Ended Wiring
(https://www.tortugaaudio.com/images/V25_singleended_wiring.jpg)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 12 Jul 2017, 06:19 pm
Hi Morten!

I'm still having problems with the impedance adjustment and my DAC and power amp are quite picky so I would really like to be able to switch between all 5 settings. Setting 1-3 is no problem but setting 4 seems to "erase" itself after finishing autocal so it goes back to 99.
Any ideas?      :scratch:

Also, how come you advised me not to buy the internal PSU for my balanced configuration and now you are using it in the new amps or is it a different new PSU? http://www.audiocircle.com/index.php?topic=151395.0
 
Many thanks!
/ Simon
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 12 Jul 2017, 06:42 pm
Hi Morten!

I'm still having problems with the impedance adjustment and my DAC and power amp are quite picky so I would really like to be able to switch between all 5 settings. Setting 1-3 is no problem but setting 4 seems to "erase" itself after finishing autocal so it goes back to 99.
Any ideas?      :scratch:

Also, how come you advised me not to buy the internal PSU for my balanced configuration and now you are using it in the new amps or is it a different new PSU? http://www.audiocircle.com/index.php?topic=151395.0 (http://www.audiocircle.com/index.php?topic=151395.0)
 
Many thanks!
/ Simon

Hi Simon,

The issue with the impedance not sticking on #4 is a reported bug that's on the "to fix" list. A firmware update will take care of that once we get it resolved.

I advised against our internal PSU because I don't like to waste my customer's money on something they don't need or that I don't think will improve the performance of the preamp. We still use that PS in our LDRx and LDRxB models because that's how they were originally designed. When we eventually update/replace those models we won't be using that PS anymore and will be using an external 12 VDC wallwart instead. The V25 board is way less sensitive to power supply quality than the V2. There's a very specific reason for that because the V2 used the incoming power directly to drive a pair of op amps in the control circuit. The V25 has a 2 stage DC-DC converter with the 1st stage being a switch mode converter followed by a second stage linear regulator. A good $10-25 12V wallwart is all you need. Anything way better isn't likely going to give you better results.

Best,
Morten
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: TheMonkey on 12 Jul 2017, 06:52 pm
Thanks a lot for a fast and good reply! You are the best!!  :thumb:
Good to hear that about the PSU, reassuring and thanks for not wasting our money on stuff we don't need!  :D
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 16 Jul 2017, 01:59 am
Morten,

Does the current firmware support Uart control for the V2.5?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 16 Jul 2017, 02:17 am
Morten,

Does the current firmware support Uart control for the V2.5?


Yes it does although I've not yet published the commands and have not really thought through possible issues interfacing with devices that aren't also at same 3.3V level as the V25 processor. UART is how 2 V25s communicate in balanced audio scenario. It's a very simple system. Runs at 115k baud, 1 stop bit, no parity.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 16 Jul 2017, 04:16 am
The Arduino Due I was planning to use is a 3.3V Uart controller. So that is good.  :thumb:

So any idea when you are going to publish the commands? On the website it mentions available upon request.

Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 16 Jul 2017, 12:26 pm
The Arduino Due I was planning to use is a 3.3V Uart controller. So that is good.  :thumb:

So any idea when you are going to publish the commands? On the website it mentions available upon request.


I'll move up the priority on the To Do list.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 25 Aug 2017, 08:02 pm
Hi Simon,

The issue with the impedance not sticking on #4 is a reported bug that's on the "to fix" list. A firmware update will take care of that once we get it resolved.

I advised against our internal PSU because I don't like to waste my customer's money on something they don't need or that I don't think will improve the performance of the preamp. We still use that PS in our LDRx and LDRxB models because that's how they were originally designed. When we eventually update/replace those models we won't be using that PS anymore and will be using an external 12 VDC wallwart instead. The V25 board is way less sensitive to power supply quality than the V2. There's a very specific reason for that because the V2 used the incoming power directly to drive a pair of op amps in the control circuit. The V25 has a 2 stage DC-DC converter with the 1st stage being a switch mode converter followed by a second stage linear regulator. A good $10-25 12V wallwart is all you need. Anything way better isn't likely going to give you better results.

Best,
Morten

So would a meanwell Switchmode PS like the IRM 12V work just fine. I was looking at using it to power the arduino and the V25 board(s), since neither seems to need a linear PS.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 25 Aug 2017, 08:44 pm
So would a meanwell Switchmode PS like the IRM 12V work just fine. I was looking at using it to power the arduino and the V25 board(s), since neither seems to need a linear PS.


For the V25 I think it would work fine. The output hits another switching DC-DC regulator on the board and then a linear regulator.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 3 Oct 2017, 02:12 pm
Yes, with dual boards you can mix balanced and single-ended inputs.

It gets a bit messy to explain/show but with balanced signals the master board handles the + phase for both the right/left channels and similarly the slave board handles the - phase for both channels. This arrangement is necessary in order for the channel balance adjustment feature to work properly.

To add single-ended inputs you would would only connect inputs to the master board's right/left channels.

The output wiring follows the same approach as the inputs. When a balanced input is selected that attenuated signal would also be present on the RCA output jacks but only from a single phase so the volume would be reduced. When a single-ended input is selected the balanced output would have a signal present on only one phase.

V25 Balanced Wiring
(https://www.tortugaaudio.com/images/V25_balanced_wiring.jpg)

V25 Single-Ended Wiring
(https://www.tortugaaudio.com/images/V25_singleended_wiring.jpg)

I was thinking of this. Could I use the second slave board as a balanced board for 2-channel use and as a single ended for multichannel use? I would have a DAC and phono inputs for 2 channel input. Both could be balanced. I would have two multi-channel inputs which are only single ended for total of 6 channels. I would switch the outputs so that the right outputs get the correct signal to the amp and speaker.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 3 Oct 2017, 09:07 pm
I was thinking of this. Could I use the second slave board as a balanced board for 2-channel use and as a single ended for multichannel use? I would have a DAC and phono inputs for 2 channel input. Both could be balanced. I would have two multi-channel inputs which are only single ended for total of 6 channels. I would switch the outputs so that the right outputs get the correct signal to the amp and speaker.

I'm probably not clear on the specific arrangement you described but will try to answer your question this way:

1) With dual boards you essentially have 4 independent channels that in theory you can use any way your want in terms of mixed balanced and single ended but with the constraints/limitations discussed in 2) below.

2) When you adjust channel balance towards the right or left you are raising the volume of one channel on a board with respect to the other channel on that same board. Withe dual boards this happens to both boards the same way at the same time. With balanced signals if we wired both phases to just a single board and then adjusted the channel balance all you'd accomplish was raising one phase with respect to the other on both left and right stereo channels - resulting in no channel balacne shift. The reason the balanced wiring is the way it is is in order for the channel balance adjustment feature to work properly. If you didn't care about channel balanced adjustment you could wire both balanced phases to either board rather than splitting the phases between both boards  (as shown in the diagram).
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 4 Oct 2017, 01:15 am
I would run the positive phases to the master board and the negative phases to the slave board as a normal configuration for 2-channel. For multichannel, I would run single ended channels 1 and 2 on the master board, single ended channels 3 and 4 on the slave board. That seems possible based on what you said. Now I just have to switch the output signals so they go to right location.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 4 Oct 2017, 01:34 am
I would run the positive phases to the master board and the negative phases to the slave board as a normal configuration for 2-channel. For multichannel, I would run single ended channels 1 and 2 on the master board, single ended channels 3 and 4 on the slave board. That seems possible based on what you said. Now I just have to switch the output signals so they go to right location.


Yep, that should work!
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: WC on 6 Oct 2017, 10:50 pm
Can you stack the boards, if you are using multiple boards? If so, how much space is needed between boards?
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 8 Oct 2017, 11:39 am
Can you stack the boards, if you are using multiple boards? If so, how much space is needed between boards?

I'm sure you can but having considered doing this myself I decided not to in order to ensure ease of access. I'd allow for 0.5 inch space below and 0.8 inch space above each board as a rough guide. The limiting item on the topside is the 5 V regulator with is about 0.75 inch tall. The bottom side has a 2x5 pin header used only for initial programming of the processor and also a pair of low profile relays active only during calibration. The version B of the V25 board in development will likely do away with both the relays and the pin header on the underside but that's not been verified yet.

P.S. Your board ships this week.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 26 May 2019, 08:52 pm
It's been awhile since we highlighted the LDR.V25 Preamp Controller as the core part of any DIY passive preamp or new/modified existing active preamp so here's to all of you DIY'ers out there...draw near and take heed!

Tortuga Audio's latest offering is the LDR.V25 Preamp Controller together with a 256x64 pixel white-on-black graphical OLED display module with encoder and apple remote. This is our 4th generation design. We use this same hardware in our commercial preamp product line.

The firmware is mature at this point with occasional minor bug fixes and/or tweaks but will remain proprietary hence we don't share the source code. The V25 runs on an ARM Cortex M3 microcontroller and is programmed in C. Updated hex code files can be downloaded from our website and uploaded into the controller by the end-user.

As a standalone passive preamp the V25 sounds great. You can also incorporate it into most any new or existing solid state or tube based active preamp with exceptional results.

Here are the highlights:

* 100 step volume control/attenuation over 60 dB range
* Muting with volume ramp-down and ramp-up
* Built-in self calibration of the LDRs - no LDR matching required
* LDRs are replaceable plug-in modules
* Can switch up to 6 stereo inputs with switching built into the board
* LDRs are also used for input switching in lieu of relays
* Mono/stereo mode controllable via remote
* Use a pair of V25 boards to handle balanced audio
* Fully remote controlled via any silver Apple remote with remote ID pairing (256 remote ID's possible)
* Adjustable input impedance between 1-99k ohms | up to 10 possible settings (#1 is 20k fixed default)
* Firmware can be updated via simple PC based bootloader program and USB cable
* Powered by most any DC source between 9 and 30 volts DC rated at 500 ma (actual demand is considerably less)
* 256 x 64 pixel graphical OLED display with interface board with mounted IR receiver module & encoder attachment point
* OLED attaches to the V25 board via a 14 pin ribbon cable which carries power, OLED, encoder and IR signals.
* Menu driven OLED display with numerous functions including
   * Turn preamp off
   * Control volume
   * Adjust left/right channel balance 
   * Switch inputs
   * Adjust display brightness
   * Adjust display timeout (blanking)
   * Change max initial volume on startup or input change
   * Change units between steps & dB
   * Show firmware version
   * Adjust impedance & update calibration
   * Reset (all impedance/calibration data)

When purchased together as a package, the LDR.V25 (equipped for 3 inputs) plus OLED display/encoder run $399.

With few exceptions, we ship most anywhere in the world.

Here's a link to the LDR.V25:  LDR V25 Preamp Controller | Tortuga Audio (https://www.tortugaaudio.com/products/diy-preamp-components/ldr-v25-preamp-controller/)

This pic of the V25 shows the Rev A version. We are now on Rev C that looks almost identical has a few parts moved around. The Rev C board switched to SPI communication with the OLED rather than the earlier 8 line parallel method.
(https://cdn2.tortugaaudio.com/20181130185949/V25_LDR_Cal_Sequence_Identification.jpg)

(https://cdn2.tortugaaudio.com/20181130185954/OLED_with_cables.jpg)

The control menu has changed slightly from the one shown below. The Impedance and Calibration items have been merged into a single Imped-Cal menu item since these are so inextricably linked functionally.
(https://cdn2.tortugaaudio.com/20181130185947/OLED_V25_Controls_Rev0-1.png)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: walterslw on 28 May 2019, 03:20 pm
Trying to connect to the Tortuga website and am receiving "www.tortugaaudio.com refused to connect."
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: srb on 28 May 2019, 03:35 pm
 (https://www.audiocircle.com/image.php?id=194982)
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 May 2019, 03:54 pm
(https://www.audiocircle.com/image.php?id=194982)


Yes, am aware the website is down at the moment and am working on resolving it. Thanks for the heads up though.  :thumb:
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 28 May 2019, 08:38 pm
Trying to connect to the Tortuga website and am receiving "www.tortugaaudio.com (http://www.tortugaaudio.com) refused to connect."

Thanks for the notice. Took a bit of work but everything's up and running again.
Title: Re: LDR.V25 (the "V25") Preamp Controller
Post by: tortugaranger on 30 May 2019, 07:44 pm
What you need to build a Tortuga Audio DIY passive preamp...

1) $399 - V25 Preamp Controller Board (3 inputs expandable to 6) with OLED display and Encoder
2)  $15  - USB port/cable (for updating firmware)
3)  $25  - Apple remote
4)  $?? - A set of RCA jacks (at least 4 for 1 input & 1 output)
5)  $?? - An enclosure of your choice or making
6)  $??  - A knob for the encoder
7)  $?? - A 12 VDC 0.5A power supply

Already have an active preamp that could use some updating? You can probably skip items 4) through 7).

What are you waiting for, just go do it!

https://www.tortugaaudio.com/product-category/diy-preamp-components/ (https://www.tortugaaudio.com/product-category/diy-preamp-components/)