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Old 23rd September 2003, 09:32 PM   #11
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Thanks. Maybe I need to try building a PP amp after all...
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Old 23rd September 2003, 09:33 PM   #12
SY is offline SY  United States
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Well, I could always replace the regulator chip on the one you've already got
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Old 23rd September 2003, 09:38 PM   #13
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Quote:
Well, I could always replace the regulator chip on the one you've already got
My wife's response to the current version of my amp: (CCS'd ECC99 driver, current regulated 2A3 heater, UBT-3 OPTs, teflon caps) - "it sounds pretty good". Her response when I completed the first iteration of my 2A3 SET (125ESE OPTs, AC heaters, straight from the Angela website) - "it sounds... off".

I've been eyeing your amp lately... I'm pretty sure mine doesn't sound as good, but I want to know if I'm any closer than I was before

What would be great would be to bring my amp down to your place some day and get a lesson or two on chasing (RF, and other) gremlins, troubleshooting, improvements, just anything
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Old 23rd September 2003, 09:51 PM   #14
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Well, I have another member coming down next weekend (weekend of the 4th) for some speaker work. If you're free, join us. We can probably fire up some dynamic speakers just so we don't torture your poor little amp too badly on the ESL panels.
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Old 23rd September 2003, 09:55 PM   #15
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Wow, that would be great! I'll try my best to be there. And I wasn't even thinking about real speakers so much as a test bench/power resistors.

I'll email you. Thanks for the offer.
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Old 23rd September 2003, 10:11 PM   #16
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Hi,

For our D'Haen:

Quote:
I've never see an engineering definition of pure Class A operation
In CLASS A OPERATION, current flows for 100% (360) of the input signal.

My guess is that the "pure" part refers to the 100% current flow although in most so-called amps it's more often than not not the case.

Cheers,
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Old 23rd September 2003, 10:13 PM   #17
SY is offline SY  United States
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Normally (but not "officially"), people use the term "pure" class A to distinguish a true silicon furnace from one of those Japanese sliding-bias units. People DO cheat the term a bit, as you imply; if you see an amp that's claimed to be 200 watts of "Class A," it had better be throwing off enough heat to roast a wildebeest.
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Old 23rd September 2003, 11:02 PM   #18
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Quote:
Originally posted by fdegrove
Hi,

For our D'Haen:



In CLASS A OPERATION, current flows for 100% (360) of the input signal.

My guess is that the "pure" part refers to the 100% current flow although in most so-called amps it's more often than not not the case.

Cheers,
That's what one would suppose, but what text book mentions the term?
And if I marketed a P-P amp that ran in limiting class A, and called it "Pure Class A", who could contradict me?

By "limiting class A" I mean including the last non-linear part of the transfer characteristic.

Cheers,
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Old 23rd September 2003, 11:20 PM   #19
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Hi,

Quote:
That's what one would suppose, but what text book mentions the term?
If you like I could doublecheck it and give you page #s frm the RDH and McGrawhill.

To my mind the description I posted is correct for all intends and purposes.

If you deviate from that you shouldn't call it a pure Class A amp.


Quote:
And if I marketed a P-P amp that ran in limiting class A, and called it "Pure Class A", who could contradict me?
I wouldn't. But then again I don't buy marketing hype either.

I know what you mean though...

My main quibble is mostly with the fact that the term is often used to market amps where, when you take a closer look it's not even close to Class A operation.
Big A small b if you're lucky.

Cheers,
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Old 23rd September 2003, 11:29 PM   #20
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I like the ones which call out "single ended" and "class A" as separate virtues, as in, "not only is it single-ended, it is *also* class A". And that too, in a linestage. How many push-pull class B linestages are there? PP maybe (or more likely, balanced or differential, neither of which would be single ended, right?), but I really wonder if there are many non-class A linestages.
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