Post by Phil Allison
FFS give up posting wild guesses as fact.
It's not like I haven't built a bunch of guitar amps since I was a
teenager, both tubes AND transistors, nor seen a number of schematics,
nor reverse engineered a Fender amp to build a custom amp based on
Fender's circuits because someone wanted me to, nor having played guitar
since the 1960's, nor having re-worked the electronics on guitars a few
times [including putting a 5 pos switch on a Hondo strat copy that had a
3 pos switch for a friend], yotta yotta.
OK - which of the things I said were "wild guesses" ?
keep in mind that the tech manuals said something I'm agreeing with.
YOU are disagreeing with the tech manuals, and after I provide several
examples based on what I've seen (particularly for older amplifiers,
where this would be more relevant), you say that I'm "posting wild
guesses as fact".
So, since I never actually DID that, then you're welcome.
A typical old amplifier:Loading Image...
(in this case 75k - I've seen as high as 220k, but on average, input
resistors on the shared input are around 100k, which if you think about
it, isn't a whole lot different from 75k or even 68k when you average it
A typical guitar (strat):Loading Image...
shows volume and tone controls are 250k. I have seen as low as 50k, but
typically 100k as I recall.
This one shows 1M volume controls on the guitar:Loading Image...
I'm sure you'll see LOTS of variability. Some old guitars [I used to
have one] even had ceramic pickups. And you also have pedal output
impedence. So the variability is pretty wide here.
My guess is that a pre-amp would be designed such that any noise
generated by an audio tube's filament would be minimized based on a very
wide range of possible inputs, single guitar, two guitars, ceramic or
dynamic pickups, 50k or 250k or 1M volume controls, etc. etc..
So if I happen to "ballpark" the values, you should be able to see why.
And I still accept what the tube spec sheet says about hum on one of the
triodes being slightly higher.