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Roland JC-120 Jazz Chorus Amp Clone

john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
Hello all,

Most that know guitar amps know that the JC-120 is THE BEST CLEAN AMP EVER - and the best Solid State Guitar amp in existence. These amps are found in all types of music - Jazz, rock and roll, metal, etc (Police - Andy Sommers, Metalica, etc)

Anyway, I downloaded the schematic (the version with 2SK117 not the later opamp version) and had a PCB fabbed with the help of a fellow DIYAudio member (Thanks Craigtone!!)

So the preamp has all the goodies including a quad of 2SK170 instead of the 2SK-117 (a deluxe version?) and behind it is a LM3886 - standard fab of Brian Bell's gainclone amp. Preamp has volume, bass, mids, treble and a Hi Treble switch. With LM3886. it's roughly 45 wpc. No reverb, chorus, etc, just the preamp / amp section. The rest you can do with pedals.

After building the amp/preamp, I bought a real Roland JC-120 Guitar amp, and surprisingly sounds very close. Bandmates were impressed!

Selling as I built another in a nicer case and it has a 200 watt/channel ICEPower 200ASC behind the JC-120 preamp.

Amp $150 + ship

Also have a few PCBs if anyone wants one - free you pay ship and you make a donation to DIYAudio site would be great.

Pics on the way...
 

john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
Pics...
 

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john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
The JC-120 Preamp Clone PCB..

Please note the four transistors Q1, Q2, Q3, and Q4 are all reversed from depiction on board for a 2SK-117 / 2SK-170. All else perfect. Found out after PCB were made...did not do a good job checking...

Voltage is 20 -35vdc (I used a 19vdc power supply from old laptop, but original amp was around 36vdc)

I also played around with this preamp going feeding a tube amp (Carvin Tube 100, two channel EL34 push - pull driven by a 12AX7) and it was awesome.
 

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Last edited:
Missed this thread way back then.

Congratulations on your project, doubly so for actually building it, getting a proper case,etc.
Many good projects don´t go beyond "a few PCBs on the kitchen table" stage, simply because the "hardware" part is often more complex (and expensive) than the purely "electronic" one.

Kudos to craigtone for the generous PCB design.

to grj2773: this is a truly transparent amplifier, even if no sound samples "you already know how it sounds" (like a JC120 that is ;) ): you will hear "the guitar" and "the speaker" used :)
 
Hello all,

Most that know guitar amps know that the JC-120 is THE BEST CLEAN AMP EVER - and the best Solid State Guitar amp in existence. These amps are found in all types of music - Jazz, rock and roll, metal, etc (Police - Andy Sommers, Metalica, etc)

Anyway, I downloaded the schematic (the version with 2SK117 not the later opamp version) and had a PCB fabbed with the help of a fellow DIYAudio member (Thanks Craigtone!!)

So the preamp has all the goodies including a quad of 2SK170 instead of the 2SK-117 (a deluxe version?) and behind it is a LM3886 - standard fab of Brian Bell's gainclone amp. Preamp has volume, bass, mids, treble and a Hi Treble switch. With LM3886. it's roughly 45 wpc. No reverb, chorus, etc, just the preamp / amp section. The rest you can do with pedals.

After building the amp/preamp, I bought a real Roland JC-120 Guitar amp, and surprisingly sounds very close. Bandmates were impressed!

Selling as I built another in a nicer case and it has a 200 watt/channel ICEPower 200ASC behind the JC-120 preamp.

Amp $150 + ship

Also have a few PCBs if anyone wants one - free you pay ship and you make a donation to DIYAudio site would be great.

Pics on the way...
Hi, im a noob here, need some help, what voltage is it powered with? And the power section is before or after de pcb? Very thanks¡¡¡