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Old 2nd May 2012, 01:49 PM   #121
tonimxp is offline tonimxp  Italy
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Greetings to all! Anyone have any suggestions for me before I mount the pcb? For example I'm thinking of replacing C4 with 15pF directly,so..i can save my time and i can not remove it all over again.
Are you agree with me?
Thanks in advance.

P.S. On the bottom Pcb as showed

First Wima 0.1uF + Ero 1860 0.01uf are in parallel with C2 220uF Silmic II

Second Wima 0.1uF is in parallel with C3 220uF Nikicon Muse
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Last edited by tonimxp; 2nd May 2012 at 01:55 PM.
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Old 3rd May 2012, 01:24 PM   #122
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Quote:
Originally Posted by tonimxp View Post
I'm thinking of replacing C4 with 15pF directly,so..i can save my time and i can not remove it all over again.
Are you agree with me?
Thanks in advance.
Toni: I'm no expert here, but on tube amps the feedback compensation cap (C4 in this case) is typically tuned/adjusted during testing to get a good square wave at 10Khz without overshoot/ringing. The final value can be somewhat hardware-dependent and can be sensitive to the specific output transformers chosen. Obviously, SS amps don't have output transformers, so like I said, I'm no SS expert.

If you want to play with the amount of feedback and change the feedback R, you need to re-check the 10Khz sq wave to see if the comp cap value is still correct.

Do you have a scope?
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Old 3rd May 2012, 07:03 PM   #123
tonimxp is offline tonimxp  Italy
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Quote:
Originally Posted by boywonder View Post
Toni: I'm no expert here, but on tube amps the feedback compensation cap (C4 in this case) is typically tuned/adjusted during testing to get a good square wave at 10Khz without overshoot/ringing. The final value can be somewhat hardware-dependent and can be sensitive to the specific output transformers chosen. Obviously, SS amps don't have output transformers, so like I said, I'm no SS expert.

If you want to play with the amount of feedback and change the feedback R, you need to re-check the 10Khz sq wave to see if the comp cap value is still correct.

Do you have a scope?
Hi!Bw i have just changed C4 with 15pF value,i think you're right, but I think by coarse analysis that 15pF should be ok, of course when I will try it i will make sure with the scope and signal generator, thanks anyway for the advice.
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Old 3rd June 2012, 12:37 PM   #124
tonimxp is offline tonimxp  Italy
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Hi to all!Today i have just start up my aleph 30. I think could be interesting some pictures.
Will be shown in order:
1) square wave test at 10 khz
2) supply voltages of one psu (my amp is a dual mono topology)
3) supply current of one psu (my amp is a dual mono topology)
4) control of the temperatures of the first cooling fin and then on the body of the MOSFET
5) check of the waveforms with tone at 10 kHz (I found 0.14 Vrms)and 100 kHz (I found 0.10 Vrms) sinusoidal,i think there is an attenuation of 3dB (Nelson says there should be about 1.5 dB).
6) I also detected a ripple voltage of 0.04 Vrms ( nelson says 0.3 Vrms but mine is a dual mono psu with uF 176000).
Do you have any suggestions for the frequency response slightly deficient on high?
Thanks in advance.
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Old 3rd June 2012, 12:43 PM   #125
tonimxp is offline tonimxp  Italy
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I remember you that i had changed C4 (10pF) with 15pF value for square wave test.
Any suggestions?
Thanks.
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Old 3rd June 2012, 01:14 PM   #126
Zen Mod is offline Zen Mod  Serbia
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leading edge/corner is rounded

try again with 10p

just for splittin' da hair sake
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Old 3rd June 2012, 01:39 PM   #127
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Just bloody listen to it you lunatic.
How perfect do you need that square wave?
Very nice work
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Old 3rd June 2012, 05:10 PM   #128
tonimxp is offline tonimxp  Italy
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Quote:
Originally Posted by Zen Mod View Post
leading edge/corner is rounded

try again with 10p

just for splittin' da hair sake
Hi Zen! Ok tomorrow i will try with 10 pF value
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Old 3rd June 2012, 05:23 PM   #129
tonimxp is offline tonimxp  Italy
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Originally Posted by Melon Head View Post
Just bloody listen to it you lunatic.
How perfect do you need that square wave?
Very nice work
Hi melon Head and thanks for the compliments, nice to write with you
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Old 3rd June 2012, 09:51 PM   #130
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Originally Posted by tonimxp View Post
Hi Zen! Ok tomorrow i will try with 10 pF value
Please post a scope shot with the 10pf cap when you test......
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