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Old 17th November 2016, 06:51 PM   #21
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Originally Posted by needtubes View Post
distortion at 25W into 8-ohm was similar, but max power distortion into 2, 4-ohms was higher in my simulation.
That's why I think it's probably some sought of Source Follower Output.
Maybe it's push pull source follower combined with a healthy amount of single ended bias like the other XA amps but without the supersymmetry circuit.
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Old 17th November 2016, 07:20 PM   #22
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clever cheapskate can always joggle with approach to and difference between balanced , symmetrical and differential .......
When I was a boy, I was bloody hopeless with Christmas Presents. Hahahaha
The suspense is killing me.

What do you think of the possibility of old school White cathode follower, could that be defined as single ended?
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Old 17th November 2016, 11:24 PM   #23
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Default XA25

Single ended INPUT. The amp is push-pull
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Old 18th November 2016, 03:29 AM   #24
plasnu is online now plasnu  United States
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From Xs manual: The original Aleph 0 from 1991 used an output stage which consisted of a push-pull Class A output stage operated in parallel with a high constant current output stage. The bias currents were high enough to operate to rated power in single-ended Class A, giving it a second harmonic signature, and as a push-pull topology at higher power levels.

Is this what you guys guess?
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Old 18th November 2016, 04:30 AM   #25
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From Xs manual: The original Aleph 0 from 1991 used an output stage which consisted of a push-pull Class A output stage operated in parallel with a high constant current output stage. The bias currents were high enough to operate to rated power in single-ended Class A, giving it a second harmonic signature, and as a push-pull topology at higher power levels.

Is this what you guys guess?
Yes this is what I have been guessing, if not, then some more Papa genius.
Good chance it might be half of a regular XA.8 amp but biased higher than normal with a large share of single ended bias.
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Old 18th November 2016, 04:35 AM   #26
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Originally Posted by Jon Ver Halen View Post
Single ended INPUT. The amp is push-pull
Thank you very much Jon, can't wait to learn more about it.
When should we expect to see these for sale?

If push-pull are you able to confirm that it is a complementary pair of N and P channel mosfets at the output, or is it a quasi-complementary push-pull output stage?
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Old 18th November 2016, 07:43 PM   #27
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According to this it's single ended.


Pass Laboratories XA25
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Old 18th November 2016, 08:32 PM   #28
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Originally Posted by woody View Post
According to this it's single ended.


Pass Laboratories XA25
Yes I've read that a dozen times.
The problem is single ended can mean quite a few different things.
I would put my faith in Jon Ver Halen since he has a very good relationship with Papa and actually sells Firstwatt products.
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Old 18th November 2016, 08:39 PM   #29
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inputs are RCA , so there is no doubt

but , from rest of text ...... there are so many choices

SE or not , figures in A/8R , A/4R, A/AB/2R ....... not so many choices for OS

are there any complementary pucks ?

I tried to find complementaries for my thyristors , but nada ....... it seems I'm doomed on mosfets
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Old 18th November 2016, 09:12 PM   #30
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Originally Posted by Zen Mod View Post
ZM knows Station

inputs are RCA , so there is no doubt

but , from rest of text ...... there are so many choices

SE or not , figures in A/8R , A/4R, A/AB/2R ....... not so many choices for OS

are there any complementary pucks ?

I tried to find complementaries for my thyristors , but nada ....... it seems I'm doomed on mosfets
There are P Channel Pucks but not true complements, having said that there is no such thing as true complementary p channel parts, and if papa intentionally creates asymmetry by adding single ended biasing in parallel, then probably no need to have complementary parts in the first place, just find the closest match with regards to current, transconductance and power rating and Bob's your uncle.
Some quasi complementary set up wouldn't be out of the question either.
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