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Old 21st February 2005, 10:11 PM   #11
The one and only
 
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The specific Zen hasn't been identified, but keep in
mind that most of them have a low input impedance.
It is possible that the signal source is doing something
at that level.

The orginal Zen did 10 watts at 2%, which is just visible
with a scope, and yes, you can figure on swinging rail to
ground, losing less than 3 volts at each end.
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Old 22nd February 2005, 02:52 AM   #12
jcayer is offline jcayer  Canada
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Join Date: Oct 2004
Quote:
Originally posted by Nelson Pass
The specific Zen hasn't been identified, but keep in
mind that most of them have a low input impedance.
It is possible that the signal source is doing something
at that level.
Zen version 1

I never tought that the source could do something like that...

I tested the BOZ with the same source (function generator) and the signal was very goog. Of course the input impedance are not the same (BOZ vs Zen v.1)

I will try to feed the Zen thru the BOZ. That might do it. I really hope that you are right, because I don't know what else to try / test beside changing the parts
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Old 22nd February 2005, 06:05 PM   #13
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Since you have a scope, you should be able to verify
all the voltages and such to confirm proper supply and
bias. Since the first Zen is so dead simple, it can't be
too hard to find the problem. If it's your source, you
should see that distortion at the input.
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Old 22nd February 2005, 06:22 PM   #14
jcayer is offline jcayer  Canada
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Quote:
Originally posted by Nelson Pass
Since you have a scope, you should be able to verify
all the voltages and such to confirm proper supply and
bias. Since the first Zen is so dead simple, it can't be
too hard to find the problem. If it's your source, you
should see that distortion at the input.

Nelson,

The input is ok, I borrowed another signal generator and made a test on my lunch hour.
Same bump...

However, I cranked the adjustment pot a bit more and the signal got better. Now, at 10W (8ohms - 1KHz) the signal is perfect. But when it reach clipping, it is not symetrical.

And I measured the dc drain voltage and the bias voltage is running at around +19.7V. (both channels)

Is it too high ??

Thanks for your input
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Old 22nd February 2005, 08:47 PM   #15
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What do you mean by Drain Voltage vs bias voltage?
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Old 22nd February 2005, 08:59 PM   #16
jcayer is offline jcayer  Canada
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Join Date: Oct 2004
Quote:
Originally posted by Nelson Pass
What do you mean by Drain Voltage vs bias voltage?


I'm sorry, I should have "reread" my post

I meant the drain voltage of Q1 and Q2... (19.7 Volts)
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Old 23rd February 2005, 12:18 AM   #17
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Normally I would have expected best performance at about
17-18 volts, but going back to the original article I note that
it says "adjust for symmetric clipping", so what's a couple
volts among friends?

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Old 23rd February 2005, 03:10 AM   #18
jcayer is offline jcayer  Canada
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Join Date: Oct 2004
Quote:
Originally posted by Nelson Pass
Normally I would have expected best performance at about
17-18 volts, but going back to the original article I note that
it says "adjust for symmetric clipping", so what's a couple
volts among friends?




Thank you Mr. Pass.

Right now I am satisfied with the signal.

I think that my confusion came from the fact that I built the BOZ first and I almost didn't have any adjustment to do. The clipping was symmetrical and very sharp right from the beginning.

Now I will try to find some time in the next couple of days (damn kids ) to plug the BOZ to the zen just to monitor the outputs and then THE big test with my cd player and my speakers...

Now I wonder, what tune shall be the first ??

Any suggestions ?
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