guitar amp starts sounding different after a while

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andre tchmil

Well-known member
Joined
Jun 4, 2004
Messages
1,654
Location
land of chicon
I have a Marshall JMP amp that sounds very nice for rock type of guitarsounds.
However , after a few hours of heavy use in a recording situation, I have the feeling that the amp starts to sounds different, (more blurry and less bright).
Is it possible that there is some component (tube, capacitor...) failing duty, and if so where to start looking at?

Or is it just ear fatigue ?
 
Or is it just ear fatigue ?

This would be the first thing to suspect. But if you're not playing loud it's less likely. 'Heavy use' does sounds like massive powerchording though...

(Apart from the tubes,) can you tell if things run hot in the amp ?

I'm not familiar with this amp, do you have a way to split the signal-flow ? Like listening to / recording a preamp out signal and see if that signal is already changed.

Peter
 
Guitar amps do sound different after they have warmed up.
Possibile factors:

Power Transformers heating up and changing voltage
Speaker magnets not liking the heat (changes the perm of the magnet)
Kind of like thermal runaway, the hotter they get...
Capacitors changing with heat
Resistors changing with heat
Tubes changing with heat (unlikely)
Output transformer Weissareas getting looser causing more saturation
(unlikely)

Power line fluactions?
(unlikely)

Ears? Most definately.
 
i am sure you are right! Hot amps change a lot.

I had a Mesa triple rectifier in the studio and tracked a whole day tru it.
Next day we needed to do some punchins and this became litterally impossible cos the amp had changed enormously (no controls moved!) from just cooling down overnight... in the end i had to redo a few songs cos we didn't get the sound as the day before and we could hear the punchins :shock:

Older amps suffer way more from this.
For this reason i don't like it when people come in with old amps and switch them on to early... The sound you're after is gone after a while...
I had (small) succes with switching valves/places...

watch out, those are very hot! (The guitarist burned his fingertips when doing - his parts were done by the other guitarist of the band) :green:
 
André,

Does your room get very hot when this amp is in there for a few hours?
from a temperaturechange of 10-15 °C you can expect to start hearing differences in the acoustics of the room too, this can even influence pitch as the caracteristics of warm and cold air are not the same.

Would be a significant temperature boost though...

tdB
 

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