A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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very interesting experiments you are up to! I hope to hear back some day, to get your feedback... I know it cost quite some effort and budget to create one tube stage which sounds great, hence I tried to avoid one extra stage by the use of a single resistor. I did many test on the I/V conversion and at the end came back to passive ;-) as said, I do like your opinion on both, so please at least try both!
 
I did many test on the I/V conversion and at the end came back to passive ;-) as said, I do like your opinion on both, so please at least try both!

I will do. I've not got any issues with passive output, other than I'll need more than 1.2V to drive my zero gain headphone buffer. I really do need 2V RMS. No issue with transformers either, other than cost. One of the best sounds I achieved was with balanced AD1865 design and a pair of Sowter I/V transformers. Using a transformer to combine the phases from your PCM1794 board and get 2.4V out SE would be fine. But I do not have any suitable transformers on hand, and I said "ouch" when I looked at the cost of the custom Sowter units you are offering. Also, I have the parts on hand to make a quick tube stage. I'd be inclined to recommend buying an Unbalancer board from Broskie, maybe for someone who doesn't want to get their hands too dirty on design, just populate the Unbalancer board, feed it with both phases from the DAC boards, no need to cap couple even with the voltage offset. But if you don't need the gain, why bother.

Just out of interest, did you not consider the Lundahl LL1674? That's what the KandK people were using for passive I/V with their PCM1794 RAKK dac. I think the Neko DAC is using Jensens for transformer out. Pretty sure that is a PCM1794 DAC. I don't doubt that the Sowter is worth the money. But 4 DAC decks plus the Sowter transformers....... Expensive!
 
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The WaveIO does not go over 192KHz but at 39€ the Amanero board does (PCM up to 384KHz and also DSD):

http://www.diyaudio.com/forums/vendors-bazaar/216474-usb-i2s-384khz-dsd-converter.html

Hi Doede! - I second the question. The Amanero is able to go beyond 24 bit and 192kHz, and seems to also be able to do DSD - can it be used with your new DAC?

[As you know, I managed to fry my old USB receiver and we discussed replacing it, but upon getting myself up to date with your latest work (and of others) I became interested in upgrading...]

Please let us know if and how can your DAC work with the Amanero USB to I2S.

Thanks!
 
Doede, I like you site. I am waiting for someone to come up with a NOS kit that has PCM1704 into tube output. Naturally USB input with at least 192/24 capability is must these days. Single-ended output is fine.

You have extensive experience in stacking multiple TDA1543 chips. PCM1704 is difficult with passive I/V; have you tried stacking multiple PCM1704s? This way I/V resistor load will be divided among multiple PCM1704 per channel.
 
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Hi Doede! - I second the question. The Amanero is able to go beyond 24 bit and 192kHz, and seems to also be able to do DSD - can it be used with your new DAC?

[As you know, I managed to fry my old USB receiver and we discussed replacing it, but upon getting myself up to date with your latest work (and of others) I became interested in upgrading...]

Please let us know if and how can your DAC work with the Amanero USB to I2S.

Thanks!

In general, my DAC will work with everything that outputs I2S signals.

For the 384kHz, the PCM1794 most likely will be able to do this, but I have not tested this. In regard to DSD stream, I as far as I could read from the datasheet, this is not supported.
 
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Doede, I like you site. I am waiting for someone to come up with a NOS kit that has PCM1704 into tube output. Naturally USB input with at least 192/24 capability is must these days. Single-ended output is fine.

You have extensive experience in stacking multiple TDA1543 chips. PCM1704 is difficult with passive I/V; have you tried stacking multiple PCM1704s? This way I/V resistor load will be divided among multiple PCM1704 per channel.

Thanks for feedback. I am very afraid, you will have to wait a long time before a kit with such tube stage will pop up that it will be worthy the DAC before it. Let’s not start talking about the Budget you need for that...

Good Thing with the PCM1794 is that it is not at ALL difficult for passive I/V if implemented well. As you can read from the site and see from the circuit values. Using a 6,1k for Rref and 8 Volt for analog supply, you can actually reach 1.2 V rms with very low distortion of only 0,4% at 0dBFS. This saves you an extra stage and avoids opamps or other complex circuits. Resulting in superb Sound and very affordable Budget to build (were important design criteria for me..)

I have not tried stacking the PCM1704. But it can be done as well, no Problem even with active I/V. The benefits of paralelling will stay. Still what could argue against the pcm1704 is the need for another amplifier stage and for all the very high price...
 
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Just out of interest, did you not consider the Lundahl LL1674? That's what the KandK people were using for passive I/V with their PCM1794 RAKK dac. I think the Neko DAC is using Jensens for transformer out. Pretty sure that is a PCM1794 DAC. I don't doubt that the Sowter is worth the money. But 4 DAC decks plus the Sowter transformers....... Expensive!

Actually I went to Lundahl as well with my expectations of bandwidth, maximum output voltage and the fact there must be room for some residual DC current, and the answer was they could not do it. Sowter could and the transformer is pretty high spec, so worth the Money. Of course other transformers will work as well, but most likely will not meet the expectations of high bandwidth in both ways and low distortion at high voltage Output. Do not forget, the Sowter does pimp up to 4,6 Volts rms
 
Doede,

My kit arrived today. Built and running. I'm intending to put together Salas shunts for both 12V and 5V for the WaveIO, but for the moment WaveIO is powered from USB bus and a quick dig through my junk box earlier turned up a transformer and 12V linear regulator mounted to a heatsink, so that is pressed into temporary service for now.

I am pleasantly surprised. I have only spent a couple of hours listening, but I'm pleasantly surprised!
 

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Nice clivem. Interested to see how far you can tweak your kit.

An externally hosted image should be here but it was not working when we last tested it.


I'm using a 12V 'audiophile' linear power supply to power the mainboard/dac and the standard usb power for the usb board.

Waiting for Doede to release the power supply kit.

I have mine connected into my Silvaweld valve preamp. Probably my favorite sounding digital combo I have owned.

Enjoy!
 
Thanks. I will try it.

But I did remember reading this from Doede's site. Does it change anything to what you have suggested?

circuits_mainboard_small.png


Mainboard

The 10 position pin headers are used for easy connection with the WaveIO Board. Please note this is a proprietary design, so not according to any standard. The LED signal section is on the main board, but is completely isolated from the other electronics. The WaveIO board is driving the LEDs with 8mA current sources. So any LED can be used, color and light intensity are not relevant. There are LEDs for the sample frequency (Fs = 44.1, 48, 88, 96, 176 and 192 kHz), Host active and Audio stream. Very helpful indications!
 
Thanks. I will try it.

But I did remember reading this from Doede's site. Does it change anything to what you have suggested?

In that case the isolation that I mentioned before isn't an issue, so please ignore that.

I have read somewhere a while ago that some LEDs can be more noisy (in terms of radiated EMI) than others, might be worth looking into that still, once everything else is optimised.
 
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Doede,

My kit arrived today. Built and running. I'm intending to put together Salas shunts for both 12V and 5V for the WaveIO, but for the moment WaveIO is powered from USB bus and a quick dig through my junk box earlier turned up a transformer and 12V linear regulator mounted to a heatsink, so that is pressed into temporary service for now.

I am pleasantly surprised. I have only spent a couple of hours listening, but I'm pleasantly surprised!

Hi Clive,

A reaction I heard many times now. it seems this dac really beats expectations... In fact it did beat mine as well. Considered me lucky ;) I see you use the standard Mundorf capacitors, a simple power supply and USB. on both sides there is much gain to be made! looking forward to your further experiments....
also with the pcm1704, specially as you have them lying around :cool:
 
also with the pcm1704, specially as you have them lying around :cool:

I think that might have to wait. ;) That I haven't switched off your DAC after a few hours listening and fired up my TDA1541A comfort blanket, says it all really. Don't quote me on this, and of course I am allowed to change my mind if I ever do implement a 1704 daughter-board, but my gut feeling is that 1704 will sound more "digital" than what you have now. There is a naturalness, a kind of organic nature, which reminds me more of old-school Burr Brown and Philips chips, more than anything else I have heard which has a sigma-delta badge, or even 1704 for that matter.

I will post some more later. But I had a most interesting time last night with mpd upsampling 44.1/16 CD rips to 176.4. (I don't have a great deal of >44.1k material, so was just playing with software upsampling redbook to 88.2 and 176.4 on the laptop.) Since then I have installed Triode's EDO plugin and kernel on my Logitech Touch (for USB DAC support and > 96k sample rate support) and currently have the DAC hooked up to that. The idea being that I could after editing a config file on the server, use sox or ssrc, to up/over sample on-the-fly. Only problem with that is that I can't go above 96k at the moment due to the Touch using wireless network. Doesn't have the bandwidth to support 176k sample rates. I'll hook up via ethernet later. Reading the John Swenson post, (linked above), I think he is onto something. If you are going to OS and DF, you can get better results doing it in software, not the filters built into the chips.
 
I hope it's not too late to bring congratulations to Doede for his work in building this "one of a kind" DAC! I came to the idea that I must have one here to play with so, Doede, soon enough please cont me in for one of your "creations". One is a generic word... I must look around to see how many PCMs I have since I like towers... (higher => better) :) I'm speaking about towers anyway, so I have a question for you Doede: how many decks do I need and where should I stop counting :)
Congratulations again for a beautiful design,
L
 
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Nice dac, and I enjoyed reading your website dddac!

This reminds me of what I read earlier from John Swenson's work from another forum on 1704 vs 1794 (NOS vs disabled digital filter mode):
Computer Audio Asylum

thanks for feedback. I checked the article from John and it was interesting in terms of getting keen on doing some next experiments with software filtering and up sampling and use some other players. Actually I never tried to listen and measure what happens if you up sample 44.1 to 176.4 or 192 and how it sounds or measure.

this week I finally get my new toy, an AP system two, so I am hoping to get some more insight by doing signal tests as well.

On a sad notice, if you read the thread of John, there is a lot of talking and opinions, but no real DIY which provides an easy route in improving sound for most hobbyists.... Nice for reading time, but not for "listening time"
 
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