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Old 28th October 2005, 09:03 PM   #11
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by Nelson Pass
I suspect the pot.

Uh huh me too..

BUt i have tired a 50 k pot a 100k pot.. What could i do to change this . Fix it.. its werd..
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Old 29th October 2005, 06:45 AM   #12
Raj1 is offline Raj1  United Kingdom
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HI,

Bottom line is this, there is no quick fix to your problem, you need another gain stage period.

Using a 50k pot requires a lower output impedence and more gain than the tube stage you have can provide.

Here are your options,

1) a solid state buffer after the tube stage. Though this obviously negates the sonic benefits of that simple tube stage

2) To somehow transformer couple the output of the tube buffer so that it can drive into low impedence loads. You could probably get away with a 10k passive pot after it then.

3) to use a tvc, so that the roll-off is not so extreme. This is my own prefered option, it is not cheap, and does not technically impress the more scientific amongst us, in terms of measurments and theories. Ping Kuei Yang Wang, he uses a system similar to your dac with a TVC, and can easily tell you what the shortcomings of your present setup are. He is busy though so getting a response is not always easy.

4) to use another tube gain stage.

Nelson has said it, it's the pot, it will work fine with most SS buffers before it, but with cap coupled tube stages like these you need an active gain stage or another of the options above...........

once you have decided on what you want to do, ask on the tubes or solid state forum about how best to achieve it. I am no expert, but have a little experience with various passive/active setups I have used.



Thanks
Raja
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