JSX Mods

prsplayer86

prsplayer86

Member
I've gotten a ragged out JSX that needs an overhaul. Looking at updating the irons to MMs and adding a Choke. Also, curious if anyone has some suggestions on other mods?

Cheers
 
I would look at amps like the peavey ultra plus 120, triple xxx for inspiration and pull the best from each channel of those amps. The JSX is just slightly different then those amps. I don’t think for what the amp would ever be worth it and for very little to be gained tonewise by putting MM iron in it. I would just get a good fresh set of tubes in it bias it up, play it and start thinking about what you would change if anything on each channel and go from there.
 
I agree with jason, I think the iron upgrade would be pretty negligible.

I would get really nice tubes, bias it up, and maybe see if there are some simple things you could do to improve the sound or ease of life upgrades.
 
Agreeing with everyone. I don't think the iron and choke will do all that much other than lighten your wallet. JSX is great as is. At most, throw a boost up front and maybe an EQ in the loop. Amp sounds great with EL34s, too.
 
I bought a used JSX off Guitar Center in late July,
and I threw some new Hi-Gain JJ's (Gain Score=11) in it for CH2 & 3,
and the amp totally thumps now.
 
jasonP said:
I would look at amps like the peavey ultra plus 120, triple xxx for inspiration and pull the best from each channel of those amps. The JSX is just slightly different then those amps. I don’t think for what the amp would ever be worth it and for very little to be gained tonewise by putting MM iron in it. I would just get a good fresh set of tubes in it bias it up, play it and start thinking about what you would change if anything on each channel and go from there.
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I have an ultra 60 combo I cut down to a head. Sounds great!👍
 
IMG_1822.jpeg

I have not finished it yet but after a retube it sounds great. Usually use the low gain input…just sounds better to me. Would love a jsx though.
 
prsplayer86 said:
I've gotten a ragged out JSX that needs an overhaul. Looking at updating the irons to MMs and adding a Choke. Also, curious if anyone has some suggestions on other mods?

Cheers
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I would recommend you swap all the caps on the main board of the amp. Peavey put some crappy caps in there and they're all rated at 85 deg. I have a head and a combo and the combo was given to me brand new as a present. I've never pushed the amp and the filter caps need to be replaced because it hums.

The biggest bang for your buck will be replacing the preamp tubes with a combination of tubes.
 
Replace the active tone controls with a standard Marshall style tone stack. I think the JSX sounds fine but I didn't like the controls anywhere but straight up the middle.
 
Purgasound said:
Replace the active tone controls with a standard Marshall style tone stack. I think the JSX sounds fine but I didn't like the controls anywhere but straight up the middle.
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That tone stack setup is super pointless. I’ve had a couple of these amps and liked them but if there was one mod I wish was doable it would be making the diode clipping switchable.
 
Bardagh said:
That tone stack setup is super pointless. I’ve had a couple of these amps and liked them but if there was one mod I wish was doable it would be making the diode clipping switchable.
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The JSX (and XXX, and Ultra, and Triumph) do not have diode clipping. It's a common misconception, the diodes you are likely seeing in the signal path reduce signal noise when the guitar signal is very quiet/off, they do not clip a signal or send partial lobes to ground etc like an actual diode clipper amp does.
 
TotallyRadGuitars said:
The JSX (and XXX, and Ultra, and Triumph) do not have diode clipping. It's a common misconception, the diodes you are likely seeing in the signal path reduce signal noise when the guitar signal is very quiet/off, they do not clip a signal or send partial lobes to ground etc like an actual diode clipper amp does.
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Well that's wild, what explains the fact that they sound EXACTLY like there is diode clipping distortion with these amps? If you know what it sounds like, you know what that means. Especially on the Crunch channel of the JSX you can hear it, it's the way that there is this always present bitey, midrange spike with some dirt around it regardless of how much or how little gain you are dialing in. There is no dialing it out, and I've never heard a pure tube amp sound anything like that.
 
kmanick said:
this^ I've had 2 Jsx's over the years and the Kt-77's add a flavor that I liked better than 6L6's or El-34's in this amp
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Aggressive. I love the JSX. It's in my top 5 favorites. I've had probably 4 or 5. Last one I sold to mylilss on here, and he did some mods. Think transformers, choke and put KT88's in it? That guy fell off the map, I haven't seen him around in a long time.
 
I have a stock / original 2100 100W 5881 JS-X on the way; should be here by the end of the week; hopefully, FedEx won't modify it on the way.
 
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