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Tube buffer for V-out DAC's

post #1 of 6
10/10/09 at 3:09am
Thread Starter 
After several years of experiementing with DAC's, I've come to the conclusion that for my ears a tube analog stage is preferred.

Now that the Wolfson 8741 is readily available I would really like to try it but I have never found a tube buffer stage that can deal with the DC offset and not have too much gain for a V-out DAC.

There were some nice ideas at TubeCad but they just looked risky using the DC offset to bias the tube. Has there been any advancements in this area?
I think there is a lot of potential here but I've really never seen an elegant design for these new chips.
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post #2 of 6
10/10/09 at 3:36am
Balanced-Ouput DACs and Tubes and Aikido

why would it be risky to use the dc offset to bias?

The other alterntaive is to just use a another cap, you'll end up using one on the output anyway.

This also looks interesting, but very complex.

http://www.diyaudio.com/forums/showt...threadid=64220
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post #3 of 6
10/10/09 at 3:50am
Thread Starter 
Quote:
Originally Posted by adamus View Post
Balanced-Ouput DACs and Tubes and Aikido

why would it be risky to use the dc offset to bias?


I would be afraid that when the tube starts conducting with power on that the DAC chip could be fried. Maybe there is no issue.


I think Runelight also has a unity gain buffer.

Good suggestion about the cap, I may give that a try.
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post #4 of 6
10/10/09 at 4:59am
Read through SY's Heretical article and use a small cap on the input and a servo on the output -- and skip the IPT.

SYclotron Audio ยป The Heretical Preamp
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post #5 of 6
10/10/09 at 6:08am
I tried a simple cathode followed on a Vout dac and didnt get on with it.

I am now just running the differential v out dac through a sowter transformer with filter. best solution i have used so far.
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post #6 of 6
10/10/09 at 12:12pm
Quote:
Originally Posted by regal View Post
I think Runelight also has a unity gain buffer.
I built the pre servo version of the unity gain buffer, it uses a cap on the output. He prototyped the OCL buffer - best check in with him how that went.

It was designed to drive long cables so I am not sure how useful it would be as a dac buffer as my understanding is that current is not a major concern in this application.

..dB


..dB
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