Re: Fender deLuxe Hot Rod ,2002

Arfa Daily <arfa.daily@xxxxxxxxxxxx> wrote in message
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"N Cook" <diverse8@xxxxxxxxx> wrote in message
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Arfa Daily <arfa.daily@xxxxxxxxxxxx> wrote in message
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"N Cook" <diverse8@xxxxxxxxx> wrote in message
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"N Cook" <diverse8@xxxxxxxxx> wrote in message
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Ron(UK) <ron@xxxxxxxxxxxxxxxxxxx> wrote in message
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N Cook wrote:




Well, not if you work on this stuff a lot, and have at least a basic
understanding of the 'musicality' of particular guitar / amplifier
combinations. If you hear a cheapo 'starter' guitar, played through a
fully
solid state amplifier more suited to vocals, or a keyboard, then listen to
say a Fender / Fender combination, you'd know what I mean. I suspect that
most on here who do this work seriously, know exactly what I'm saying.


Now if you could point to a site that has electrograms and spectrum
alalysis
plots, and sound files, of differnet guitars/pickuups/amps/cabs being
played
in different modes along with , (consensus if possible) muso "technical"
language in their terms, their audio description, then it would indeed
be
a
very useful addition.
With an extra file giving sound files of common fault conditions
simulated,
ie fault induced clipping rather than musical effect, pops , hiss,
crackle,
hum, buzz, half complementary pair signal, etc that techies could point
owners to, for such noises appearing intermittently and rarely on the
work
bench.

Despite what some on here would sometimes have you believe, occasionally,
it
*is* just subjective. I would actually think that it would be pretty
difficult to analyse the difference to the point of being able to
demonstrate it, technically. By suggesting that this was 'not your thing',
I
intended no offence to your abilities. I know many engineers that are very
good in many fields, but not in the repair of valve amps. I am sure that
there are others out there who, unlike me, are properly musical, that have
a
far better ear for problems than I do.

As an example, a few months back, I had a valve band amp in that just
'didn't sound right'. The owner said that it was quiet, and sounded
'thin'.
It wasn't actually all that quiet, but maybe a little compared to what he
was used to. 'Thin' was a good description of the sound. You couldn't
really
say that it lacked in bass, or any other register really. It just sounded,
well thin ! With a sine wave and a 'scope and a power load and meter,
there
was barely anything amiss with the output waveform or power level. The one
thing that did show on the 'scope, was a slight asymmetry to the wave, but
it was slight, and could have easily been missed. The problem turned out
to
be the screen feed resistor on one of the output valves (just a 2 rather
than a 4 valve lineup). It was completely open, so there was no screen
voltage on that valve at all, which would have meant that it was barely
working, so you might have expected to have seen a much more distorted
waveform at the output, as you would have with a semiconductor amp.

When the resistor was replaced, and that valve's contribution to the
output
stage was restored, there was little difference in either the overall sine
output power, or the waveshape, but the sound was now much better than
before. It now sounded 'right'. Now I know that doesn't explain the
mechanism of why or just how it sounded 'thin' before, and 'round' after,
but as an engineer doing a lot of this stuff, I knew that it was now
repaired, and the owner agreed. He made a point of calling the shop, and
telling them how 'good' (there we go again ...!) it sounded compared to
how
it had for some time. So I make no excuse for using phrases on here like
that I used with the Fender ...

Arfa



So what did this faullt look like graphically on a scope ?
Terms like 'thin' and 'round' may mean something to some musos but they mean
absolutely nothing to me. How am I suppose to know whether that is how
another muso prefers his amp to distort, that way, in normal use ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


.

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