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Old 1st April 2012, 11:00 PM   #1
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Default Need help choosing a discrete IV stage

I recently completed a DAC with NOS AD1865 and a salas shunt regulators I now need to decide on a IV stage for it I want it to be solid state and discrete. I have found two circuit that look the best to me the "Pass D1 IV" and the "Pedja Rogicīs Discrete Diamond Non-Feedback I/V Stage" I would like to know which one of these circuits have the best performance "subjectively" (sound quality) - test figures THD, ect.
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Old 3rd April 2012, 01:47 AM   #2
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Silicon chip an Australian magazine recently published a dac that ised a discrete I to v stage. It was a reasonably conventional discrete op amp, which in my mind was the right choice. The measured performance was very good indeed.

Most of the silicon chip stuff is published in Europe under a magazine (guessing here) named something like epn

I am sure there would be an Aussie or kiwi who has a copy of the article. FYI they used a cl4398 dac but that should not affect the approach to I to v

Last edited by googlyone; 3rd April 2012 at 01:48 AM. Reason: Typo
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Old 3rd April 2012, 03:07 AM   #3
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Borbely published several discrete dac analog stages in Audio Amateur/Xpress in the 1990's mid to late 200?. Even the early one is still worth building.
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Old 3rd April 2012, 11:43 AM   #4
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Quote:
Originally Posted by benproiii View Post
I recently completed a DAC with NOS AD1865 and a salas shunt regulators I now need to decide on a IV stage for it I want it to be solid state and discrete. I have found two circuit that look the best to me the "Pass D1 IV" and the "Pedja Rogicīs Discrete Diamond Non-Feedback I/V Stage" I would like to know which one of these circuits have the best performance "subjectively" (sound quality) - test figures THD, ect.
To determine which one has the best subjective sound quality will require that you audition both with your own ears. Simply wire both I/V circuits on individual breadboards and compare.
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Old 3rd April 2012, 11:52 AM   #5
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Default EUVL CEN I/V

If you don't need an I/V input impedance of less than several Ohms, you should definitely consider the EUVL CEN I/V. Excellent performance !
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Old 3rd April 2012, 08:24 PM   #6
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Thanks I will compare the two stages when I get the parts to build them.
Also, I built the Pass D1 IV and there in a slight amount of hum. the layout is good (ground plane). the the wires are all hooked up good. could the hum be caused by no signal at the I-Input (I have no DAC chip yet.)?
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Old 3rd April 2012, 09:05 PM   #7
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Here is the Silicon Chip one for the CS4398 mentioned in the second post, correct me if I'm wrong but isn't the CS4398 a voltage output dac.

Cheers George
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File Type: jpg Silicon Chip CS4398.jpg (351.5 KB, 498 views)
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Old 3rd April 2012, 11:35 PM   #8
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That is a v-out dac the dac chip i use (AD1865) is i-out.

Does anybody have any experience with the Pedja DDNF stage there is not many comments about it's sound quality. I want to know if it's worth building?
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Old 6th April 2012, 07:09 PM   #9
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I am using Pedja's DDNF on a homebrew pcb with TDA1541a... I like it very much, but have little to compare with. I just know I like it a lot more than SRPP tube stage....
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Old 6th April 2012, 09:18 PM   #10
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I have some experience with the AD1865, as I've designed and built two different DACs using it. The AD1865 is relatively rare, in that it is a current output DAC with a high output voltage compliance. This enables the use of a passive resistor I/V, which is the best performing type of I/V, assuming the DAC has a high voltage compliance, which most don't. I've used I/V resistor values as high as 330 ohms on AD1865 without problem. I find that passive I/V with this DAC chip subjectively supremely clean sounding.

What passive I/V with the AD1865 further enables is the A.C. coupling of the DAC output to your linestage without any intervening circuitry. Most solid-state linestages have enough gain for this, most of which is thrown away anyhow, with typical 2VRMS DAC output voltage levels. The output impedance will be the 1.7K ohm AD1865 output impedance in parallel with whatever value of I/V resistor you've slected. In other words, it will be low enough to drive your quite effectively.
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