Push pull amps.

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valvesRus
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Push pull amps.

Unread post by valvesRus »

I had a short listening session with a World Designs 6550 push pull amp the other day, and I was pleasantly surprised at the "fullness" of the presentation.

So, today I am reacquainting myself with an old friend, my first amp build, the 832a push pull amp.

I remembered it had a fault last time out (many,many years ago) so I tested it and found one of the 832a was dodgy, so I swapped in a replacement and all seems well. I gave it a once over and removed all the dust and cobwebs while it was on the bench.

Because the 832a is two valves in one envelope, with a shared cathode, and a CCS in the cathode, it will only operate in class A.

So now it's in the main system and playing a few favourites. :D

Lurcher300b
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Re: Push pull amps.

Unread post by Lurcher300b »

it will only operate in class A
Why do you say that?

It can still be driven to the point where one of the valves shuts down. It will just do so very badly.

valvesRus
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Re: Push pull amps.

Unread post by valvesRus »

Lurcher300b wrote: Wed Oct 23, 2019 12:16 pm
it will only operate in class A
Why do you say that?
Well Nick, from memory it was your good self that told me, but I might have misunderstood you. :)

Lurcher300b
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Re: Push pull amps.

Unread post by Lurcher300b »

valvesRus wrote: Wed Oct 23, 2019 12:26 pm
Lurcher300b wrote: Wed Oct 23, 2019 12:16 pm
it will only operate in class A
Why do you say that?
Well Nick, from memory it was your good self that told me, but I might have misunderstood you. :)
I am sure you will find the quote to disprove me, but what I would have mean is it can only operate in A, anything else will sound broken unlike a normal output stage will move into B without anything obvious. Just consider if you have the CCS set for 50ma, and you apply a signal on one of the valves grids that would require the valve to pass 51ma, the other valve by definition will be shutdown, so not in A.

valvesRus
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Re: Push pull amps.

Unread post by valvesRus »

Lurcher300b wrote: Wed Oct 23, 2019 1:23 pm
valvesRus wrote: Wed Oct 23, 2019 12:26 pm
Lurcher300b wrote: Wed Oct 23, 2019 12:16 pm

Why do you say that?
Well Nick, from memory it was your good self that told me, but I might have misunderstood you. :)
I am sure you will find the quote to disprove me,
Even if I could, it would seem churlish. Thanks for reiterating the way things work with regard to class A and AB the way my 832a is configured.

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