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Kofi Annan in: "Tube Amp for Multi-Way Speakers"
Kofi Annan in: "Tube Amp for Multi-Way Speakers"
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Old 29th October 2019, 03:07 AM   #151
Kofi Annan is offline Kofi Annan  United States
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Quote:
Originally Posted by Adolf Corkscrew View Post
That's actually a quite nice response for a 10kHz square wave. I wouldn't worry. The slight resonance - if I read your scope trace right - seems to be at around 50kHz and well damped, so if the amplifier is otherwise stable I wouldn't do anything.


You could measure the amp to other impedances, that might give a different response. Maybe a 47 ohm resistor instead of an 8 ohm dummy load. And try a 2,2F cap in parallel with the 8 ohm dummy and see if the amplifier is still stable. Some overshoot with a cap in parallel with the resistive dummy load is to be expected, but the amplifier should still be stable. If this is true, don't worry.
I'll do a little more measuring tomorrow and post the results. It honestly sounds so good to me that I'm inclined to leave it alone.

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The amp looks great!, and from your description it sounds great as well. Great job!
Thanks, Scott. Really appreciate all your help.

It's still nagging me that I have 6.53V on the heaters instead of 6.3. Should I be worried about it?

Kofi
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Old 29th October 2019, 01:27 PM   #152
scott17 is offline scott17
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Great. That's only ~3.5% high, that's fine. I believe accepted close tolerance is +/- 5%.
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Old 29th October 2019, 01:49 PM   #153
Salas is offline Salas  Greece
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Kofi Annan in: "Tube Amp for Multi-Way Speakers"
Try NFB from the 8 Ohm output tap also
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Old 29th October 2019, 11:41 PM   #154
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Originally Posted by Kofi Annan View Post
It's still nagging me that I have 6.53V on the heaters instead of 6.3. Should I be worried about it?

Kofi

That's a non-issue. Well within tolerances. Stay under 6,7 volts and it's A-OK.
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Old 30th October 2019, 12:01 AM   #155
kevinkr is offline kevinkr  United States
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Kofi Annan in: "Tube Amp for Multi-Way Speakers"
Check at high typical line for your area and if you are under 6.7V or so you should be fine.
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