I'd like to get your input on product development options

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poseidonsvoice

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Re: I'd like to get your input on product development options
« Reply #20 on: 13 Apr 2015, 11:59 am »
You don't need any coupling caps with the jfet buffers.   Please see this thread:   http://www.diyaudio.com/forums/pass-labs/145201-building-symmetrical-psu-b1-buffer.html    for info on the circuit and using shunt regulators.  You don't need an output resistor either.

No, I was not suggesting using a solid state buffer with a tube line stage....but two separate products....a solid state buffered unit for lower output impedance and a separate tube output stage version (offering gain and buffering and the highly desired tubey sound).

What you are talking about (your SS suggestion) it seems is the DCB1. This is something I have mentioned to Morten in pm's previously. All info is on diyaudio, and the boards are available at the diyaudio store (or PM Tea-Bag on diyaudio for a version without input selection)complete with shunt regulator supply if you don't want to build breadboards (and I imagine Morten would not). It's a great sounding buffer, but would be better with Morten's LDR :wink:

Best,
Anand.

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #21 on: 13 Apr 2015, 12:16 pm »
This is not what I was talking about. When I had the original LDR3 in my system while it was on tour I was able to test it with an amp that had a volume control. Whether I listened to the amp with the LDR in the system or out of the system I couldn't here a difference. That's why I think using an LDR as a volume control only would be a great product, no gain, just a remote volume control for any active preamp that doesn't have one.

I think there's some confusion regarding your comment so perhaps this will help clarify.

All of our preamps are LDR passive volume controls.
All have no gain.
All have remote control.
Some have input switching.

I believe you are suggesting substituting any active preamp's volume control (typically a potentiometer) with Tortuga LDR volume control (without input switching).

For me the confusion with your comment is that what you are describing is basically what our stuff already is and does. Depending on how it's applied.

gregfisk

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Re: I'd like to get your input on product development options
« Reply #22 on: 13 Apr 2015, 04:27 pm »
I think there's some confusion regarding your comment so perhaps this will help clarify.

All of our preamps are LDR passive volume controls.
All have no gain.
All have remote control.
Some have input switching.

I believe you are suggesting substituting any active preamp's volume control (typically a potentiometer) with Tortuga LDR volume control (without input switching).

For me the confusion with your comment is that what you are describing is basically what our stuff already is and does. Depending on how it's applied.

 Thank you Morten for clarifying what I was saying, I guess it was so simple it was confusing?

Yes, a small box no gain, no additional inputs, just a remote. This would keep the cost down and be for anyone who has a preamp without a remote who likes the sound he is already getting but wishes he had a remote.

Someone just recently sold a Dude preamp and the person said they loved it but just couldn't live without a remote anymore, when I'm looking at buying a new preamp like many others I look to see if a remote is available for it, if not I move on. Like I mentioned it would be an add on product to your line up not a replacement.

I do like the idea of a tube buffer stage as well, many people like adding them for gain or to add tube flavor to their system. And if it has volume control all the better.

underdog64

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Re: I'd like to get your input on product development options
« Reply #23 on: 18 Apr 2015, 06:06 pm »
As someone who owns an EVS modded Oppo BDP-105 I would love to replace my active tube pre with a Tortuga Active tube pre with an LDR attenuator for a volume control.I would replace it now but I can't do passive as good as the JFet output stage is on the Oppo it lowered the output voltage.Could one be done with a battery power supply? That would be perfect- an LDR volume controlled active tube pre that runs off a battery supply like the Dodd tube buffer only with an LDR for volume control and just a slight bit of gain.

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #24 on: 19 Apr 2015, 02:59 pm »
As someone who owns an EVS modded Oppo BDP-105 I would love to replace my active tube pre with a Tortuga Active tube pre with an LDR attenuator for a volume control.I would replace it now but I can't do passive as good as the JFet output stage is on the Oppo it lowered the output voltage.Could one be done with a battery power supply? That would be perfect- an LDR volume controlled active tube pre that runs off a battery supply like the Dodd tube buffer only with an LDR for volume control and just a slight bit of gain.

Our first version will be solid state but we have a tube version in the works as well. As it stands now the SS will have an op amp gain stage in front of a JFET buffer - no coupling caps on either the input or output.

I'm a bit skeptical as to how practical powering the tube version with a battery would be due to the higher current draw of tubes not to mention the voltage level. If we went with low voltage "space charge" tubes then it's at least a possibility but I suspect we'd need fairly large batteries. Space charge tubes work fine but tend to have higher distortion levels. We'll definitely look into it before making a final decision.

rajacat

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Re: I'd like to get your input on product development options
« Reply #25 on: 19 Apr 2015, 03:20 pm »
How about an app for smartphone/tablet remote control? :eyebrows:
The apple remote works good enough but its very small, easy to lose in the bowels of my Lazy Boy and seems a bit delicate. Also its always good to get rid of one more remote and consolidate.

33na3rd

Re: I'd like to get your input on product development options
« Reply #26 on: 19 Apr 2015, 03:31 pm »
Our first version will be solid state but we have a tube version in the works as well. As it stands now the SS will have an op amp gain stage in front of a JFET buffer - no coupling caps on either the input or output.

I'm a bit skeptical as to how practical powering the tube version with a battery would be due to the higher current draw of tubes not to mention the voltage level. If we went with low voltage "space charge" tubes then it's at least a possibility but I suspect we'd need fairly large batteries. Space charge tubes work fine but tend to have higher distortion levels. We'll definitely look into it before making a final decision.


If you were going to use tubes, I would prefer an easier to source tube with good sonics than a Space Charge Tube. NOS tubes are great, but they're becoming more scarce everyday. Some of the new New Sensor tubes tubes sound pretty good, like their 6CG7/6FQ7. I specifically mentioned the 6CG7/6FQ7, as it is one of my favorites. The sound of a 6SN7 without the microphonics!

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #27 on: 19 Apr 2015, 03:40 pm »
How about an app for smartphone/tablet remote control? :eyebrows:
The apple remote works good enough but its very small, easy to lose in the bowels of my Lazy Boy and seems a bit delicate. Also its always good to get rid of one more remote and consolidate.

This is one of our "back burner" projects. The issue isn't designing/coding an app for both iOS and Android but the lack of IR ability is many smartphones. To use your iPhone or iPad for example you would need an additional wifi to IR converter thingy for this to work. Or, we'd have to add a wifi receiver to the next version of the LDR3x board but that would leave all existing boards in the lurch. I occasionally do look into this but have not found the right universal solution - perhaps there isn't one - yet.

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #28 on: 19 Apr 2015, 03:44 pm »

If you were going to use tubes, I would prefer an easier to source tube with good sonics than a Space Charge Tube. NOS tubes are great, but they're becoming more scarce everyday. Some of the new New Sensor tubes tubes sound pretty good, like their 6CG7/6FQ7. I specifically mentioned the 6CG7/6FQ7, as it is one of my favorites. The sound of a 6SN7 without the microphonics!

The 6CG7 (9 pin version of the 6SN7 octal) is my tube of choice for our tube products. I only mentioned the low voltage Space Charge tubes in the context of low voltage (12 V) battery powered.

33na3rd

Re: I'd like to get your input on product development options
« Reply #29 on: 20 Apr 2015, 04:44 pm »
I really like the LDR units as they are, so clean & sweet!

I realize that some amps would benefit from a buffer and/or higher gain.

Would it be possible for the out board buffer to offer additional gain too? Perhaps 6dB? Could you have the gain module in the buffer unit, instead of the LDR unit? Or would the extra interconnects negate any advantages?

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #30 on: 20 Apr 2015, 05:18 pm »
Would it be possible for the out board buffer to offer additional gain too? Perhaps 6dB? Could you have the gain module in the buffer unit, instead of the LDR unit? Or would the extra interconnects negate any advantages?

Both buffer types (SS or tube) will have some degree of adjustable gain from unity to +?dB. The gain adjustment will be on the buffer board and will be independent of the upstream LDR attenuator. I don't know yet how we'll handle the gain adjustment. Could use a pot or perhaps even discrete resistors tied to switch. The gain is something you only adjust infrequently to get sufficient volume control headroom.

Physically I think the SS buffer will fit nicely within our existing enclosure designs so can be ordered as a option including a bypass switch. Will probably also package these as stand alone buffer units without any volume control for placement downstream of an existing LDR passive preamp.

The tube version will be physically larger by necessity so will definitely not fit within existing smaller enclosure package. Still sorting that out.

robertopisa

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Re: I'd like to get your input on product development options
« Reply #31 on: 23 Apr 2015, 06:08 am »
My 2 cents :)

- Dual grounding scheme for balanced version: play vs calibrate. I did it and it works.

- Shielding the analog path through LDRs from the rest of the board, which is digital.

- Improving the ergonomics of the Apple remote as it is overloaded of functions (use also the enconder + remote for setting impedance, display, calibration, etc.)

- Avoiding to use switching regulators: at least giving this as a paid option, eg using Belleson regulators.

- Making firmware devoted to balanced version as it is different from the single ended version, eg impedance is doubled.

Great job so far, but the path to the hell is still on :) Thanks.

-Roberto

P.S. I am against using buffers, IMHO, as this alters the cool passive nature of Tortuga. A person sold his VTL 7.5 pre (yeah, that expensive VLT pre) as his balanced DAC was more transparent without, so using just the internal volume of the DAC. After trying my balanced DIY Tortuga, probably changed mind... he asked me if the Tortuga had a gain... of course no!

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #32 on: 23 Apr 2015, 01:31 pm »
My 2 cents :)
- Dual grounding scheme for balanced version: play vs calibrate. I did it and it works.
I think I know what you're getting at here but I would ask you to elaborate please.

Quote
- Shielding the analog path through LDRs from the rest of the board, which is digital.
To be clear the audio signal path in the existing design is both physically and optically isolated from the analog control path. However to your point the analog control does share a power supply with the digital and these will be separate supplies in the next design iteration.

Quote
- Improving the ergonomics of the Apple remote as it is overloaded of functions (use also the enconder + remote for setting impedance, display, calibration, etc.)
I agree and options include: a) Reorganizing certain control functions into a "maintenance mode" which has to be enabled otherwise it operates as a simple remote;  b) Moving to a custom remote. This has its advantages but carries a hefty up front capital cost to get unit cost down. Plus the idea of yet another  custom IR remote just seems so old school and annoying; c) Moving to a "soft" remote app for both iOS and Android. The biggest obstacle here is the lack of universal built-in IR in all smartphones but this could be done with a simple low-power wifi interface in lieu of IR interface or alternatively an intermediary wifi-to-ir device external to the product itself.

Quote
- Avoiding to use switching regulators: at least giving this as a paid option, eg using Belleson regulators.
I will disagree as to the idea that switching regulators are somehow inherently inferior to linear regulators in audio applications. The regulator we currently use is actually quite a nice bit of hardware and far superior to the ubiquitous LM9XXX series we used in the V1 model. That said, it's certainly not a super-regulator like the Belleson. Which by the way we are in the process of evaluating. Also, more recently there are some newer ultra low-noise linear regulators from TI and others that rival super-regulator performance. All of those are surface mount components. Also, anyone daring enough with a solder iron can swap out the existing regulator for a Belleson. Just get one with a LM78xx pin configuration and around 400-500 ma capacity. Be very careful removing the existing regulator which is rather beefy - easy to bugger the pads or lift a trace.

Quote
- Making firmware devoted to balanced version as it is different from the single ended version, eg impedance is doubled.
This may best be solved by multiplying by 2 in the interim but I get your point.

Quote
P.S. I am against using buffers, IMHO, as this alters the cool passive nature of Tortuga. A person sold his VTL 7.5 pre (yeah, that expensive VLT pre) as his balanced DAC was more transparent without, so using just the internal volume of the DAC. After trying my balanced DIY Tortuga, probably changed mind... he asked me if the Tortuga had a gain... of course no!
In my view there's a small contingent of early adopters who are open to the idea of using passives generally and within that small contingent there's a subset that may eventually discover Tortuga LDR passives and see the light!

However, I think the vast majority of audio enthusiasts are quite convinced that the only good preamp is an active preamp - evidence to the contrary notwithstanding. Thus a buffer option opens up the possibility of appealing to a larger market that may be willing the embrace the benefits of LDRs as long as it comes with the requisite familiar buffer/gain (i.e. it's an active preamp). Said differently, give the customer what he wants. Of course then there's Steve Jobs who said the customer doesn't know what he/she wants until you give it to them. Perhaps a buffer/gain bypass switch is in order.  :green:

justubes

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Re: I'd like to get your input on product development options
« Reply #33 on: 26 Apr 2015, 09:03 am »
- Avoiding to use switching regulators: at least giving this as a paid option, eg using Belleson regulators.
I will disagree as to the idea that switching regulators are somehow inherently inferior to linear regulators in audio applications. The regulator we currently use is actually quite a nice bit of hardware and far superior to the ubiquitous LM9XXX series we used in the V1 model. That said, it's certainly not a super-regulator like the Belleson. Which by the way we are in the process of evaluating. Also, more recently there are some newer ultra low-noise linear regulators from TI and others that rival super-regulator performance. All of those are surface mount components. Also, anyone daring enough with a solder iron can swap out the existing regulator for a Belleson. Just get one with a LM78xx pin configuration and around 400-500 ma capacity. Be very careful removing the existing regulator which is rather beefy - easy to bugger the pads or lift a trace.

How's the preliminary testing with the Belleson 5v regulators in place of the switching supply.

There are some <0.8uv regs that you mentioned, woud these be better than Belleson, newclassD, Hynes supplies. It seems that these new regs have finally come up with some excellent specs.

As i am already using a low noise supply feeding 12v to the boards and wonder if there is much room for improvement.



tortugaranger

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Re: I'd like to get your input on product development options
« Reply #34 on: 26 Apr 2015, 04:59 pm »
How's the preliminary testing with the Belleson 5v regulators in place of the switching supply.

I'll know more by the end this week and will update then.

justubes

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Re: I'd like to get your input on product development options
« Reply #35 on: 29 Apr 2015, 05:24 pm »
I have successfully swapped the 5v with a tps7a4700 low noise unit, its sharing a 5v output for both channels. Time for some fun.

performance wise it it worth while adding a small tantalum or maybe 20uf electrolic to each ldr unit soldered directly to the legs?

We'll share the resjlts this weekend :thumb:

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #36 on: 30 Apr 2015, 07:44 pm »
I have successfully swapped the 5v with a tps7a4700 low noise unit, its sharing a 5v output for both channels. Time for some fun.

performance wise it it worth while adding a small tantalum or maybe 20uf electrolic to each ldr unit soldered directly to the legs?

We'll share the resjlts this weekend :thumb:

The TPS714700 has great specs but I believe it only comes in a tiny 5x5mm VQFN surface mount. How did you package it up to fit the LM78xx/T220 3 hole spot where the stock regulator lived?

I don't think there's anything to be gained by putting a cap across the LED (control) legs of the LDRs. That's essentially a steady state DC signal that only changes when changing volume.

Iv'e suspected for some time now that the upstream 2 stage op amp introduces quite a bit of noise. It's a lowly quad LM324 which has been around forever and is a workhorse single voltage opamp. The LDR3x uses it, along with a reference voltage, to bracket the lower and upper limits of control voltage to the LDR which is driven by DACs upstream of the op amps. We run the output of the main gain stage into an adjacent op amp used only as a unity gain buffer. Frankly I don't know why we added the buffer but like all design decisions it seemed like the right thing to do at the time - and it was there anyway for the using. The buffer really isn't needed and I think it introduces considerable noise; at least in this op amp. I've been meaning to try bypassing that buffer opamp which would probably require cutting the legs off the buffer end of that chip and then adding a short jumper to connect the output of the gain stage to the where the output of the buffer would've been. This would end up looking like a messy tweak but I suspect it would reduce noise on the control signal to the LDR.

justubes

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Re: I'd like to get your input on product development options
« Reply #37 on: 1 May 2015, 05:49 pm »
I cut the swithing regs out and yes, the tps7a4700 is on its own board which i wired to the 5v connections.

There is  better  microdetailing which i believe is due to improvement in noise, no change to tonality.

I bought it of ebay andit worthwhile improvementm costing slightly more than the switching regs, but i share the 5v for my balanced boards.

How was the belleson reg?

Also can you detail the bypassing of the buffer,how do i hardwire to bypass.

Im all in for your next improved board, it's fantastic as it is now.

justubes

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Re: I'd like to get your input on product development options
« Reply #38 on: 2 May 2015, 03:07 pm »
Hi Morten,

I looked up the lm324. Its a 4 channel with + and - for each channel's output.

To bypass, do i join the inputs + and - for each cannel to its respective single output (1 to 4) and cut pin 4  which is vcc.

Is there any other considerations with removing the buffer?

Would replacing will a OPA4134 be any use?
« Last Edit: 2 May 2015, 04:11 pm by justubes »

tortugaranger

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Re: I'd like to get your input on product development options
« Reply #39 on: 3 May 2015, 02:35 pm »
Hi Morten,

I looked up the lm324. Its a 4 channel with + and - for each channel's output.

To bypass, do i join the inputs + and - for each cannel to its respective single output (1 to 4) and cut pin 4  which is vcc.

Is there any other considerations with removing the buffer?

Would replacing will a OPA4134 be any use?

To isolate and bypass the buffer op amp sections I would pull the lm324s and cut off pins 5, 6, 7, 8, 9, 10. Those are the pins on the end facing the LDRs. Then I would try to insert jumpers between pin sockets 5 and 7, and between 8 and 10. Put the clipped LM324 back in their sockets making sure the stub ends of the clipped off pins are not touching the jumpers you put in the sockets.

To be clear I've yet to try this but it should work. Worst case you bugger up a pair of op amps that cost 25 cents each.

I don't think the opa4134 would work since it doesn't appear to be suited for single supply operation. There are surprisingly few substitutes for the lowly Lm324. The few bipolars I've tried have not worked. I suggest first confirming whether the above bypass helps before rolling op amps. This is purely a steady state DC application of this op amp so things like speed aren't really relevant. Stability, low noise and PSRR should be all positives.