Roland JC-120 Breaking Up

[mikewolfe]

So I have an 80s Jazz Chorus that I got in a sorry state. Basically the thing was wired out of phase and was so dirty most of the pots either didn’t work or crackled horrendously. After a speaker rewire and cleaning it’s a gigging amp again.

Now I play in a pretty loud band, where I want tons of clean headroom, so the JC was the perfect solution. To preface, I play a fender with lower output pickups. I’ve noticed my JC has been breaking up at high volumes (past 2 o’clock or so). Anyone know if this is just the nature of the beast or a deeper problem in one of the gain stages? It sounds fantastic at “normal” volumes but it feels like it distorts way easier than its reputation led me to believe. Would love some insight or if anyone has experienced anything similar.

[Jon Snell]

This is not a high powered amplifier. It has two 60 Watt (if you are lucky) amplifiers that work against each other most of the time and may not be suitable for your application. A bit like a modern day Line 6 combo, all tin and no whistle.

[J M Fahey]

pretty loud band, where I want tons of clean headroom

my JC has been breaking up at high volumes (past 2 o’clock or so)

That is a LOUD setting, in a LOUD environment.

ALL amps break up above a 6 or 7 setting, on a 10=full scale.
Some do that gracefully yet are "considered" clean (which they are not, just scope them and you´ll see ample peak clipping) ; others, specially SS ones, clip"harsh" and are immediately noticed. Such as yours, but also Valvestate, Laney, Peavey, most any SS amp.

easier than its reputation led me to believe

Oh, "reputation"

People endlessly quote and repeat each other without actual experience.

JC120 power amps are as generic plain vanilla SS amps as can be, got a technically undeserved "reputation" of clean sounding only because famous Musicians use them strictly within the clean area (hint: way lower than "2 o clock/7")
From Metallica to George Benson to anybody in between.

So Plan A is to lower volume slightly to get back into the clean area and call it a day.

Plan B is to get a special SS amp with built in limiters so they never ever clip.
Want ear bleeding LOUD CLEAN sound?: as an example use one of Peavey Pedal Steel amps or BB King´s favorite Lab Series L5.

Important part of their act is using a very loud, efficient and clean speaker such as an EVM15L , a Black Widow, etc.

Plan C: If inconvenient or hard to find, you can build a very loud and clean setup with:
Pedalboard/Preamp of your choice > a power amp with limiters engaged (many have built in ones, such as Peavey DDT, just read the brochures) > EVM12/15L or *efficient* (100dB) Celestion or Eminence speakers.

But easiest/cheapest is to lower current amp volume somewhat and if necessary mike it through the PA.

Again, nothing "magic" about JC series amps.

[glebert]

I would try to run each side of the amp separately to see if the distortion occurs in each side. I would just disconnect one speaker at a time. Are you using the normal or the chorus channel? I would try both if you haven't already.

[J M Fahey]

Try that to clear the field, but I think nothing is "broken", it´s just being driven into the "crunch" area.

Power amp is plain vanilla, nothing special there to avoid clipping (no limiters at all)

[J M Fahey]

^^^^^ that is one Roland channel, basically same as what´s used in theold Cube 80 , aPeavey Bandit, etc.

While this beast of an amp below is used in Peavey Nashville 400
It will never ever clip at ear splitting levels:



it has a circuit called DDT (Distortion DeTector) which does exactly that, tightly controls the power amp (which is a very well made 200W unit) squeezing down to the last clean Watt.

It constantly compares speaker out and signal in and at the smallest difference it triggers a state of the art (way back then) Studio quality Compressor/Limiter.

It can hold its own even today.

And why doesn´t *everybody* use these for loud clean sounds?

1) "Jimi Hendrix never used it" , feel free to substitute any Guitar God name there.

2) Country Players used them: "oh those ridiculous guys using Cowboy hats and Texan boots".

JC120 is the *only* acceptable "clean" amp "because Metallica used them".

Oh well.