Justin & Jerry's Hifi Blog

I think Jez was explaining earlier that there shouldn't be any impedance issues to sort.

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Originally Posted by Macca

You wouldn't care to have punt at what is going on technically?

Is this a band aid for a flawed system> Is it benign distortion? Are there unknown impedance issues being sorted? I appreciate it would be shots in the dark.

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I believe I've already said maybe 3 times that I think the most likely reason I got a subjective improvement is that my prototype power amp probably likes to see a low impedance at it's input. I have no other explanation and would not want to speculate.

Generally speaking there is no reason why a buffer should improve anything unless you are driving very long interconnects like 10M long or maybe 30M long from a passive pre or other high ish output impedance source, In which case a buffer will prevent the loss of treble.

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Originally Posted by Yomanze

As your DAC will have a passive output I think the buffer will be bringing a lot to the party, also think it will work well with a passive pre...

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It will have an active low impedance output which does not require a buffer.

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Originally Posted by Arkless Electronics

It will have an active low impedance output which does not require a buffer.

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If Jerry is using his TDA1543 DAC this one uses passive resistor-based I/V & no active stage.

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Originally Posted by Yomanze

If Jerry is using his TDA1543 DAC this one uses passive resistor-based I/V & no active stage.

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I have better things to do than start researching this but it is very unlikely that it has a passive output.

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Originally Posted by Arkless Electronics

I have better things to do than start researching this but it is very unlikely that it has a passive output.

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It's a current-output DAC, and one of the only ones that can be driven directly from an I/V resistor, usually by jacking the voltage up to 8V to get the desired 2V output. Lots of TDA1543 DACs are built in this way. :)

Nearly all DACs are current output. Hence the I/V op amp stage universally used. I'm afraid it's not a topic that interests me....

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Originally Posted by Arkless Electronics

I think the most likely reason I got a subjective improvement is that my prototype power amp probably likes to see a low impedance at it's input.

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Yes, I was reading something recently where the author talked about a lower impedance drive to a power amp producing lower distortion. It might have been in one of Douglas Self's books but I can't say for sure and I can't remember the details. I'll come back if I remember.

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Originally Posted by RothwellAudio

Yes, I was reading something recently where the author talked about a lower impedance drive to a power amp producing lower distortion. It might have been in one of Douglas Self's books but I can't say for sure and I can't remember the details. I'll come back if I remember.

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Improved stability margin and/or greater immunity to RF incursion my guess.

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Originally Posted by Arkless Electronics

Nearly all DACs are current output. Hence the I/V op amp stage universally used. I'm afraid it's not a topic that interests me....

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Obviously not considering that most modern DACs have a voltage output. The opamps are used as gain stages or buffers rather than for I/V conversion. Of course vintage players are different, at a time they were all current output...