Re: stereo amp cleaning

Smitty Two wrote:
In article <2Lo7i.6745$5j1.1214@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Mark D. Zacharias" <spammenot@xxxxxxxxxxxx> wrote:

Smitty Two wrote:
In article <J%f7i.62157$V75.33167@edtnps89>,
"Dave" <dspear99ca@xxxxxxxxxxxxxxxx> wrote:



Has technology evolved so that a momentary crossing of speaker
wires could not destroy expensive output transistors?

It hasn't as much to do with technological evolution as it has to do
with intelligent design. Hasn't there always been good stuff and bad
stuff? A good design would allow you to hard wire the speaker leads
together and go fishing.

Sorry. From a technical standpoint, that is an idiotic statement,
one that has been made before, and disproven time and again. People
like to make statements like "This amp will drive a nail!" etc but
it simply isn't true. It is the nature of bipolar transistors, in
fact any semiconductor, that they cannot carry current much beyond
their rating for more than a split-second. The instantaneous current
demanded by a short-circuit will destroy ANY semiconductor output
device unless that device is being so limited that it cannot produce
music, which is dynamic in nature. Any protection circuit is there
simply to protect the speakers from an amp failure, and to protect
the amp only if the overload isn't too severe. This presumes that
the sensing circuit will sense a large (but not TOO large) current
surge prior to total failure. Any circuit which would really protect
the amp from a short circuit would also protect it from the music.


Mark Z.

I stand corrected. Maybe my ignorance is the reason I'm still
listening to tubes.

Yeah, I was going to mention tubes but I'd already gone on too long...

Tube amps don't like short circuits either, but due to the physical
constuction and current limitations of the tubes themselves, plus the ohmic
resistance of the transformers (small though it is) they won't ordinarily be
damaged by a short, especially one of short duration. McIntosh solid state
models using output transformers are also somewhat less likely to be damaged
by a short.

I need to stop here - I'm a repair tech, not an engineer. If I go on too
long, I'm liable to stray into engineering theory, which I try not to do,
since I'm not qualified, and the real engineering types around here will be
forced to waste time correcting me...

Enjoy your tube stuff ! Have a good one...

Mark Z.


.

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    ... could not destroy expensive output transistors? ... protection circuit is there simply to protect the speakers from an amp ... and to protect the amp only if the overload isn't too severe. ... presumes that the sensing circuit will sense a large ...
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  • Re: stereo amp cleaning
    ... could not destroy expensive output transistors? ... protection circuit is there simply to protect the speakers from an amp ... and to protect the amp only if the overload isn't too severe. ... presumes that the sensing circuit will sense a large ...
    (sci.electronics.repair)
  • Re: stereo amp cleaning
    ... A good design would allow you to hard wire the speaker leads ... protection circuit is there simply to protect the speakers from an amp ... and to protect the amp only if the overload isn't too severe. ... presumes that the sensing circuit will sense a large ...
    (sci.electronics.repair)