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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <firstname.lastname@example.org> <email@example.com> <3DKC9.467$Lq.firstname.lastname@example.org>
Subject: Re: Class B amplifiers: what are the large low-value resistors for?
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Date: Thu, 21 Nov 2002 07:37:46 -0000
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Phil Allison wrote:
> "Kevin Aylward" wrote in message
>> Phil Allison wrote:
>>> "Kevin Aylward" wrote in message
>>>> *Pure* class B dose not require temperature compensation.
>>>> Temperature compensation is to compensate the *bias* current. If
>>>> there is no bias current, there is nothing to compensate. The
>>>> reason for this misunderstanding could be that is usually to say
>>>> class B as shorthand, when in fact one rarely uses class B, it is
>>>> always class AB, i.e. there is at least some standing current.
>>> ** Many commercial power amps produced since the late 1960s
>>> operate with the main output devices completely cut off at idle - or
>>> pure class B. The Crown DC300 and DC300A were early examples along
>>> with most later Crowns and Phase Linears and many clones.
>> I meant *real amplifiers*:-)
> ** You know what that is do you ? I doubt it.
Oh...I think so.
>> Crown DC300's were crap, despite their reputation.
> ** That completley idiotic remark reveals a lot about you Kevin
> and it is not good.
In what way was it an idiotic remark? Are you claiming that the 1MHz fts
of the 60's resulted in a state of the art high power amplififier on a
par to a design of say the 80's and later?.
> I don't see why
>> they would bother to prevent the outputs being slightly on.
> ** Part and parcel of the design.
And a poor one at that to not to have any bias on the output.
> It sounds like a right silly idea, probably
>> because it was done 30 years ago when they didn't know any better.
> ** No arrogance is beyond you is it ?
It is a daft idea to have no bias (quad dumper and such like excluded).
I am sorry if you consider this arrogance. If it were a good idea, it
would be done more often. Essentially, it is never done. I agree that no
bias saves the manual pot setting, but this is something better lived
with than having the outputs cut-off.
>> still remember using 100 watt transistor amp modules that used a
>> driver transformer because the designers were too daft to realise
>> that the product did not have any glass in it.
> ** Unlike yourself no doubt who has too many glasses in him.
Look, we all make silly mistakes in our lives, pretending otherwise is
just as daft. Some tube designers of the past moving into transistor
design simply could not get their act together. They took approaches
which had no technical justification at the time.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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