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-   -   Universal hi-end hybrid output stage for DAC (http://www.diyaudio.com/forums/digital-source/216980-universal-hi-end-hybrid-output-stage-dac.html)

audiodesign 29th July 2012 04:03 PM

Universal hi-end hybrid output stage for DAC
 
pcb ready

USB DAC 2 - Hi-Resolution System

It can be used with any balanced output DAC chip like AD1955, PCM179x, ES9018, CS439x, AK439x.

dirkwright 30th July 2012 02:43 AM

OK.... passive I/V via some resistors to ground from the grid of each vacuum tube with a mosfet follower on the plate of each tube? How is this high resolution again?

audiodesign 30th July 2012 05:01 PM

Passive I/V work very good with new DAC like PCM179x and AD1955 .

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The component list with the cost has been published, I hope the kit will reduce the total cost.

Jay 30th July 2012 06:40 PM

Wow, I thought I was wrong going in similar direction, or I was just too lucky that it sounded so good. So it is not a bad direction at all. But the resolution really depends on the quality of the power supply. Must be decided by listening test. Shunt, coils...

dirkwright 30th July 2012 08:39 PM

All I meant was that it's been shown that a passive I/V resistor's value strongly affects the distortion performance of current output DACs. The lower the resistor's value, the lower the distortion. So, I don't see passive I/V as being the highest possible resolution, though my own design doesn't have a zero input impedance either, but it's pretty dang low. Anyway, good luck with your project.

Ken Newton 1st August 2012 01:31 AM

Quote:

Originally Posted by audiodesign (Post 3108265)
pcb ready

USB DAC 2 - Hi-Resolution System

It can be used with any balanced output DAC chip like AD1955, PCM179x, ES9018, CS439x, AK439x.

Can you tell us more about your preference for the AD1955 over the PCM179X? I have already read the very brief comments given in the DAC comparison chart on your homepage, but I'm hoping you might provide a more in-depth opinion on those two chips.

stephensank 1st August 2012 03:34 AM

The feedback loop in an active i/v stage does FAR more damage to the sound that the potentially higher noise floor of using a low value resistor for i/v.

audiodesign 2nd August 2012 08:07 AM

The comparison between the DAC chip was carried out with various listening sessions with different people and with different equipment in order to have an objective result and not subjective.
The AD1955 chip is the result most relevant to reality sound.

audiodesign 2nd August 2012 08:11 AM

New info has been published about the complete project.

USB DAC 2 - Hi-Resolution System

analog_sa 2nd August 2012 09:03 AM

Quote:

Originally Posted by dirkwright (Post 3109619)
All I meant was that it's been shown that a passive I/V resistor's value strongly affects the distortion performance of current output DACs.



Strongly? Has been shown? Can you show figures? Harmonic spectra?

Current output dacs are not all the same. Within limits most can tolerate output voltage without particular rise in distortion. Ime 20-30ohms at the output of 1794 work just fine. No clue about the 1955 though.

Besides, even if there is a minor rise in distortion, it's insignificant in the context of a tube output stage.


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