[tortugaranger]

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!!! 

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

[vvoid]

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?

[kernelbob]

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

[vvoid]

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! 

[tortugaranger]

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.

[vvoid]

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.

[tortugaranger]

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.

[kernelbob]

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

[vvoid]

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.

[tortugaranger]

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) 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.

[tortugaranger]

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

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



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.

[craig sawyers]

Looking good, Morten!

Will the IO3LDR be backward-compatible with the V2.1?

[tortugaranger]

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.

[craig sawyers]

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

[Ric Schultz]

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.

[tortugaranger]

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.

 

 

[craig sawyers]

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

[tortugaranger]

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

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.

[craig sawyers]

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!"

[tortugaranger]

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.