JTM45 mod

[hebaton]

What would hapend sound wise if I took a good quality JTM45 clone, split the V1 cathodes and use plexi values for the cathode bypass ?

Thank you !

[sluckey]

What would hapend sound wise if I took a good quality JTM45 clone, split the V1 cathodes and use plexi values for the cathode bypass ?

Thank you !

One channel would sound darker than the other. If you also change one plate cap to .0022µF then you would almost have a JMP 1987.

[hebaton]

So then I would get tone choice from mixing the channels ?
even without changing the plate cap ?

[thetragichero]

i don't think a properly-built jmp would need an anode bypass cap

[Lynxtrap]

i don't think a properly-built jmp would need an anode bypass cap

Coupling cap. They went from .02 to .002 for the bright channel in the plexi.

[Stevem]

Try it and find out, you will not harm anything.

[hebaton]

I remember seeing a schematic for a switch doing that but can'T seem to find it anymore.
Does anyon here know where I can get that ?
( a schematic for aswitch between split cathodes with pexi bypass values and original spec... )
I aasume doing that AND a tube / SS rectifier would result in pretty much two amps in one box...

[hebaton]

What would hapend sound wise if I took a good quality JTM45 clone, split the V1 cathodes and use plexi values for the cathode bypass ?

Thank you !

One channel would sound darker than the other. If you also change one plate cap to .0022µF then you would almost have a JMP 1987.

I was looking at schematics from JTM45 and 1897X not seing that change. DId I miss something.
Also, finding my JTM45 has no clean headroom. beaks up as soon as past 1,5 with humbuckers... things to look at ?

[Roe]

What would hapend sound wise if I took a good quality JTM45 clone, split the V1 cathodes and use plexi values for the cathode bypass ?

Thank you !

a jtm45 is a plexi in a fairly paradigmatic sense. do not use the split catode 820R w. 330uf or the 2k7/.68u - it will ruin the jtm tone

[pdf64]

… my JTM45 has no clean headroom. beaks up as soon as past 1,5 with humbuckers... things to look at ?

Have you verified that it’s working properly, stable, and has a reasonable clean power output?

The JTM45 uses a somewhat different OT spec to later models.

[bepone]

hebaton probably wants to say that amp develop first max volume /at 1 or 2/10, and then is developing the gain, like every non master volume amp

so gain from the amp is possible only after passing max volume. yes, this is how it is working, very "negative" functionality, specially in this modern times where nobody needs loud music. having JTM is a problem. what a paradox.
so or to add master volume, or to do some other mod. or use it like pedal platform keep gain on 1, and use the drive pedal.

[hebaton]

hebaton probably wants to say that amp develop first max volume /at 1 or 2/10, and then is developing the gain, like every non master volume amp

so gain from the amp is possible only after passing max volume. yes, this is how it is working, very "negative" functionality, specially in this modern times where nobody needs loud music. having JTM is a problem. what a paradox.
so or to add master volume, or to do some other mod. or use it like pedal platform keep gain on 1, and use the drive pedal.

NO, I am not, I've heard, played at least one other JTM45 before. IT had agreat clean for a bit before it started breaking up. THis one has basically "No" clean headroom. Yes I am looking at mods that would give it a split personality, one I could switch on and off, but I am also wondering why it does not seem to have the basic JTM45 tone at low "gain" settings !

[hebaton]

Where would I find a desing for tube to solid state rectifier ?

[sluckey]

I am also wondering why it does not seem to have the basic JTM45 tone at low "gain" settings !

This seems to be a problem that needs to be fixed BEFORE doing any mods. New tubes may fix the issue.

Where would I find a desing for tube to solid state rectifier ?

Just get a plug-in SS rectifier. Then you can easily swap between SS and tube rectifier. Weber sells them.

[bepone]

IT had agreat clean for a bit before it started breaking up.

correct , JTM has beautiful clean. if you have 0 clean you have problem with your amp somewhere.
this is my clone with merren transformers, played on the clean/crunch transition.. recorded with some old analog casette camera
https://www.youtube.com/watch?v=ijTtwRXXCrY