A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) - Page 3 - diyAudio
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Old 26th November 2012, 07:28 PM   #21
dddac is online now dddac  Germany
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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!
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Old 26th November 2012, 08:43 PM   #22
clivem is offline clivem  United Kingdom
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Originally Posted by dddac View Post
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!

Last edited by clivem; 26th November 2012 at 08:56 PM.
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Old 28th November 2012, 04:19 PM   #23
Rax is offline Rax  United States
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Originally Posted by Jackal29a View Post
The WaveIO does not go over 192KHz but at 39Ä the Amanero board does (PCM up to 384KHz and also DSD):

USB to I2S 384Khz - DSD Converter
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!
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Old 29th November 2012, 12:16 AM   #24
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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.
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Old 29th November 2012, 06:14 AM   #25
dddac is online now dddac  Germany
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Originally Posted by Rax View Post
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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Old 29th November 2012, 06:27 AM   #26
dddac is online now dddac  Germany
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Originally Posted by new2hifi View Post
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. Letís 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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Old 29th November 2012, 06:36 AM   #27
dddac is online now dddac  Germany
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Originally Posted by clivem View Post
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
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Old 4th December 2012, 12:06 AM   #28
clivem is offline clivem  United Kingdom
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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!
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Old 4th December 2012, 01:24 AM   #29
tuyen is offline tuyen  Australia
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Nice clivem. Interested to see how far you can tweak your kit.

Click the image to open in full size.

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!
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Old 4th December 2012, 01:48 AM   #30
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An idea for experiments ... try without the WaveIO LED (I think this is J9 on the WaveIO) indication cable connected.

You are negating the benefit of using isolated I2S by passing ground noise on computer/waveio side through the ground connection to the DAC board at the LEDs.
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