JC Clean Channel of Roland Cube - How It's made?

[DDD]

A friend of mine likes JC Clean channel of his Roland Cube-60 combo very much and uses it almost all the time.
AT the same time he says he don't need power amp section and speaker since he takes line-level signal from the line output of the combo.
So he asked me if it is possible to build just JC Clean section with tone control (Bass-Mids-Highs-Presence knobs) in a box.
To my regrets I cannot find modern Roland Cube-60 schematics.
Moreover, some people say that JC Clean channel is a digital emulation of a famous Jazz Chorus combo and so it's impossible to make its DIY  version.
Any useful info is appreciated.

[bancika]

why would you clone an emulator of something? It's true, cube is digital, so you can't diy it. I'd just get a schematic of JC and build that.

[DDD]

Well, good idea...as good as idea just to buy JC as it is ;-))))

[DougH]

JC120 schematics are out there on the internet. I would try the preamp (without the distortion section) and maybe the chorus if you want the signature chorus sound. Stock up on op-amps. Doesn't look horribly difficult though. A JC120 preamp could be a fun & useful project. Have fun!

[DDD]

Chorus section of the JC combo is not interesting.
I've asked some more guitar players and all of them say they like JC combo for its sound.
So I think JC stompbox emulation (including its speaker cabinet) is to be quite popular project.

[Rodgre]

As a long-time JC user, I would say that the preamp might be nice to emulate. I'm not so sure about the speakers in the 120 combo though. I'm not sure that Mouser or Small Bear sell ICE PICKS!



Roger

[Hides-His-Eyes]

is the discrete or the op-amp version the 'definitive' Jazz chorus?

Either way, it looks very doable from the FIS schematics.

[DougH]

Chorus section of the JC combo is not interesting.

Sez who?

The sound that marked an era, methinks...

[defaced]

is the discrete or the op-amp version the 'definitive' Jazz chorus?

I am also interested in this.  I wanted to try the JC and the Twin clean circuits in my amp, but I've never done the leg work to figure out which JC circuit is "the" one, or if there is one that's considered the "best". 

[DDD]

Chorus section of the JC combo is not interesting.

Sez who?

The sound that marked an era, methinks...

It's just my personal opinion.

[DougH]

Sounds pretty cool in stereo, from  what I recall. Used to love Belew's sound in 80's KC.

[Moddjobbs]

Im pretty sure the chorus in the first JC120's Is at least based off of, if not the same circuit the boss CE-1 had.

[Mike Burgundy]

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossce1.jpg
and
http://www.blueguitar.org/new/schem/_ss/roland_jazz-chorus1.gif
http://www.blueguitar.org/new/schem/_ss/roland_jazz-chorus2.gif

[Processaurus]

is the discrete or the op-amp version the 'definitive' Jazz chorus?

Good question, I have 3 of the older discrete jazz choruses (it just kind of happened over time) and have played through the opamp versions that clubs have in their backline, and hear a difference and prefer the discrete models' sound.  It's a higher voltage (~30v if I recall) circuit with lots of JFET's.  The preamp does something flattering for guitar, there is a difference in tone between running it flat and plugging an un EQ'd guitar into the power amp input.  The simpler channel of the 120 should do it, since you don't need chorus, reverb, or the infamously bad distortion.

[Hides-His-Eyes]

The op-amp is at +-15V, so it's not a headroom issue (unless it's the preference of the LESS headroom of the discrete version)

[DDD]

I'm almost sure that Cube combos' circuitry also emulate the very specific "taste" of JC speakers, that cannot be directly reproduced by Cube speakers.

[DDD]

There are some messages in some forums that say that changing JC-120 speakers with another brand speakers "kills" special JC-120 sound magic.