Hello, I have a brief question: I have a Roland cube 15, I hate the built-in distortions it has (overdrive, distortion, metal, metal stack) Their sound aren't even close to the stompboxes counterparts from BOSS (the same company). Opening the amp I saw 4 JRC 072BD. Do you suggest swapping the opamps? Any sugestion on how to improve the sound? (Like: "use xxxxx opamp for metal and xxxxxx for overdrive")
It's my understanding that the Cubes use COSM effects, which I BELIEVE are digital. So changing the opamps wouldn't really do anything for you.
Even if you were to change them, while some may disagree the opamps themselves wouldn't change the sound in any real appreciable way.
This is the old series cubes. They use analog distorion. The x series uses COSM. Maybe changing the diodes as well... I have a couple germanium diodes laying around. I will experience a volume decrease, but i dont mind
Quote from: cordovaplata on April 10, 2014, 03:57:45 PM
This is the old series cubes. They use analog distorion. The x series uses COSM. Maybe changing the diodes as well... I have a couple germanium diodes laying around. I will experience a volume boost, but i dont mind
What diodes are in there currently? Switching to germanium will give you LESS volume, not a boost depending.
Yes, my bad, LED's increases, germanium decreases ;)
Well... They are a zener-like orange/yellow mini's... Probably 1n914?
Quote from: cordovaplata on April 10, 2014, 04:01:48 PM
Yes, my bad, LED's increases, germanium decreases ;)
Well... They are a zener-like orange/yellow mini's... Probably 1n914?
Yeah it will be a decrease then. Not sure what the schematic looks like but the diodes probably would make any opamp changes m00t, however TLC2262 (which is what is used in a lot(all?) tech21 products seems to have a more pleasing clipping but again you might not hear any differences since the diodes more than likely already clamp the signal.
Not that great picture but you'll have an idea. I will trace the entire board and see if I can change at least diodes an caps to help with the EQ (http://img.tapatalk.com/d/14/04/11/sebu2ehy.jpg)
Have you tried any of the DIY dirt boxes yet in front of it? Reason I ask is you have a fairly low post count, so not sure if you're new the the scene in general or just this forum, but it might be worth trying out the various DIY circuits and run them into the amp clean.
My thoughts exactly. I'm kinda inactive in this forum due to my Job. but yeah... I could chain my favorite schematics and build them.
Quote from: cordovaplata on April 10, 2014, 05:40:20 PM
My thoughts exactly. I'm kinda inactive in this forum due to my Job. but yeah... I could chain my favorite schematics and build them.
I wouldn't necessarily CHAIN them, but build separate pedals in separate boxes for total control.
Overdrive: any typical TS variant.
Distortion: Lots of options here but one of my favs is the BSIAB2
Metal: Dr Boogie.
first things first. get a schematic of this amp and post it. then we can have a look/see and (maybe) make suggestions for "improvements" to the analog f/x in the amp. ;)
Changing the OpAmps will not really effect much how the circuit works and sounds since OpAmp is a pretty generic design element. Common to them is that they all have insanely high open loop gain, and the closed loop gain of the circuit and the feedback within practically normalizes their performance in almost every regard.
There could be slight differences regarding noise and perhaps in frequency response if you swap OpAmps with high input Z to ones with low input Z. Other than that... I'd rather focus on tweaking the surrounding circuitry.
Diode swaps... yeah, they can do something. But consider this: At least in Cube 15XL all the overdrive "channels" share a single diode clipping stage and what the selector switch does is that it alters pre and post distortion EQ'ing in several stages of the amp. Basically, the circuit reconfigures itself with the aid of FET switches to introduce very different kinds of frequency responses. THAT's the most substantial audible effect you are hearing. Not opamps or diodes. If it doesn't sound right then you need to reconfigure those filters to do so.