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In Reply to: RE: Potentiometer - Volume Pot posted by gusser on January 04, 2017 at 18:50:28
It's not the output impedance of what's feeding the pot that matters, it's the output impedance of the pot and that will be determined by the position of the pot.At the -6db point (equal resistance either way from the wiper) a 250k ohm pot will have an output impedance of 62.5k ohms and that assumes the source impedance feeding the pot is zero ohms. (a 100 ohm source feeding the pot will increase that number but only by a tiny fraction)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 01/04/17Follow Ups:
That's correct. My point is that with an OPAMP drive on the source, the input impedance of the tube power amp first stage is not that important.Now if he has a Dynaco PAS-3, then we might have a problem!
Edits: 01/04/17
Now I get what you're saying.
You're saying he could use a 10k pot and the source would still be happy and the Miller of the first tube in the amp would be more than satisfied.
Sorry I mis-read you.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
An op-amp would destroy the sound of the amp.
What is your source? it's it's a typical CD player, you most likely have an OPAMP driving your new amp like it or not!Now if you are using a turntable with a tube preamp, different story altogether.
And seriously, modern OPAMPs designed for audio are practically transparent with noise floors below any source material you can find.
Tubes are fun but let's not discount our vast technology advances since then. But then there are plenty of people here who like to implement tube I/V stages in their CD players and outboard DACs. So if you really hate OPAMPs, you can still have tubes with your CDs!
Edits: 01/04/17 01/04/17 01/04/17
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