Boss CE-2 distort/clip on attack, is this normal? Audio Clips included.

[Bornhorst]

Hello all!
I just bought a Taiwanese Boss CE-2 from craigslist.  I picked it up as a smaller alternative to the CE-1, which i already own.  One of my complaints with the CE-1 was the level control being active, even with the effect off.  This was a problem in a live setting with other pedals, because I would end up distorting the CE-1 when I switched on a another pedal and my signal level changed.  So, I figured the CE-2 would be a similar sound without the distorting and signal degradation problems.

Much to my dismay, I plugged in the CE-2 and got distortion.  This occurs mainly in the bridge position on the attack.  I have a humbucker at the bridge and a single coil in the neck position.  It also happens when the pedal is bypassed.  This leads me to believe that its an issue with the buffer, but I'm not sure.

Having never played another CE-2 before, I don't know if this is a problem that all CE-2's suffer from, or if its a problem with mine.

I recorded a direct signal into my interface, then routed the same signal to the amp by itself, next the CE-2 bypassed, then the CE-2 engaged. I did this for both the neck and bridge pickups.  The problem is most present in the files named Bridge_CE-2_Bypass.mp3, and Bridge_CE-2_Wet.mp3

http://drop.io/stompboxing
you can play the tracks in the browser by clicking the file name.

I have spent a fair amount of time searching the forum with no luck.  I've tried adjusting the trim pot on the board, and used both batteries and 9v adapters but neither did anything to fix the problem.

I would greatly appreciate any help I can get.

Thanks

[zeeman]

What brand/model amp are you using and what guitar/pickups are you using?

zeeman

[Bornhorst]

I'm using a fender american strat with lace sensor pickups at neck/middle, and a duncan JB humbucker at the bridge into a solid state peavy special 130. 

The gain is set very low on the amp to the point where I dont get any breakup with the guitar directly into the amp.

[JasonG]

There are plenty of boss pedals out there that have been damaged by adaptors. If your lucky the problem is just some dirty pots or loose connections. The ce-2 schematic is all over the web. I would suggest you check it out, the pedal has problems.

[R O Tiree]

If it's an old pedal, it might be due for a re-cap. Boss are notorious for using cheap and cheerful electrolytic caps with, in many cases, "only just" enough headroom (this pedal is no exception). There's a thriving market in re-capping old DD-2s and DD-3s, for example. It's entirely possible that a cap on its way out is dragging Vbias out of whack...

Click here for the schem.

That trim-pot (I could only find one on the schem) adjusts Vbias into the input and output buffers, the 2 low-pass filters and the JFET dry/mix switch. The LFO has its own, separate, Vbias arrangement. Measure the Vbias that you're getting now at the wiper of that trim-pot. If you can get 4.5V, then that should be OK. If you can't get it up to 4.5V, then C18 is probably shot (and I'd replace all the other electros at the same time).

Try that first and then...

The input buffer on the CE-2 increases its gain as frequencies increase. The output buffer does the exact opposite. What this means is that any remaining clock-whine from the BBD/-6dB per octave filters gets pushed right down towards the noise floor. Saves all that tedious mucking about with expensive compander chips. Ibanez use the same system in their flanger and chorus pedals.

What this means is that a high-output pickup might produce enough signal to make the input buffer clip at high-ish frequencies.

If a Vbias of 4.5V can be achieved then, in order to stop the clipping at the input buffer, you might try replacing R6 with a 33k (it's connected between pins 6 and 7 of the buffer opamp). This will drop the amount of gain that high frequencies are given (it will, obviously, also drop low-frequency gain as well). You'll also need to drop R22 to 33k as well, in order to preserve the "exact opposite" drop in high-freq gain (and boost of low frequencies).

This mod might make the pedal a bit noisier, in which case it's time to put it back to stock, slap it back on craigslist and then get another chorus pedal.

[Bornhorst]

I just measured the voltage on the wiper of the trim-pot. It was 4.05v at the highest.. Do you think that's low enough to warrant replacing capacitor C18?, or should I look elsewhere?

Thanks to everyone for their help

[CJOHNW]

Old thread so I maybe speaking into the wind here, but I found this post as I too had a distorted CE-2.

I did both Monte Allum mod and cap refresh which improved it but didn't get rid of it.

After reading the info here, I adjusted the trim pot VR3.

Interestingly the bias voltage was already very close to 4.5v.  Changed to exactly 4.5v and problem worse.

In the end I found increasing this voltage to around 4.6/4.7v , the distortion completely went away!

I wonder if this could be explained?  Perhaps it indicates a fault elsewhere?

Thanks
Colin