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VFET amp Bourns trimmer exchange
VFET amp Bourns trimmer exchange
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Old 10th June 2021, 09:39 PM   #31
ggetzoff is offline ggetzoff  United States
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Quote:
Originally Posted by MEPER View Post
I could probably find a serial combination that works.
Would be difficult to make it so it also looks good.
I hope a new trimmer solves it which should arrive next week.
I would try the fixed resistor approach while you wait if you can get the value right.
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Old 11th June 2021, 06:23 AM   #32
MEPER is online now MEPER  Denmark
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Quote:
Originally Posted by Zen Mod View Post
passive pre is important reference

good quality preamp must have same amount of details, but also bringing improved dynamics

if both of these aren't there, preamp eeznoogood
With the relative low gain of VFET amp it is possible to just connect DAC out directly to VFET amp just for a reference test (it will be quite loud then). VFET amp is as easy to drive as preamp. Then pure VFET sound can be evaluated.

An Edcor with multiple outputs could be fun and just have a selector as Vol. control.....

The output noise from VFET itself is very low. A preamp will always add some noise......
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Old 11th June 2021, 06:24 AM   #33
MEPER is online now MEPER  Denmark
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Quote:
Originally Posted by ggetzoff View Post
I would try the fixed resistor approach while you wait if you can get the value right.
New trimmers arrived and a new one installed and problem solved. No problems since then.
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Old Yesterday, 08:27 PM   #34
MEPER is online now MEPER  Denmark
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I can now say that "noise" is back in right channel!
So trimmer was not the issue.

If we say it is flicker-noise in VFET. I know noise is random but can such noise suddenly stop for some seconds / minutes and then come back and change in intensity. Sometimes audible also in mid-range speaker?

But only with ear close to speaker units.

I will check with oscilloscope to see if it is possible to see anything but my scope may not be sensitive enough.
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Old Yesterday, 08:47 PM   #35
Soundhappy is offline Soundhappy  France
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..noise is back Please Meper don't give up,
this thread is more interesting now Best regards
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Old Yesterday, 09:16 PM   #36
MEPER is online now MEPER  Denmark
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What I see on scope on both channels is that ground noise looks the same. I measure at 1mV/div with X1 probe. Probe probably picks up also from environment as I see 2mV pp high frequency noise.....or so.

Difference is that L-channel.....the horizontal midline is of signal is stable while R-channel the signal jumps up and down (very random).....lets us say.....1-2 mV and this fits with the "clicking" or "poping" noise I hear with ear close to units.
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