Boss Ce 1 Noise

[fuzzboy]

I've got a Boss Ce1 that when there's no input, it's quiet. When i play something, and as the note or chord decays, the delay/ rate noisy swoosh can be heard. It happens in both the chorus and vibrato mode.

Should i replace the electrolytics, or is it something in the delay gate section? Thanks for all your help.

Paul

[Mark Hammer]

The FET-based gate used in the CE-1 was implemented largely because of that very noise.  The assumption was that when there was a note to be heard, the background noise would not be noticed (i.e., it would be "masked" by the instrument sound).  The threshold is set such that the delay signal (and noise) *should* cut out before the S/N ratio declines to the critical point where you notice the noise.  Since the FET is envelope-driven and has a decay rather than punctate off action, and since the clean signal is always present, the moderately fast disappearance of the delay signal at the mixer should not be noticeable. 

It MAY (and that doesn't mean necessarily) be that the preset threshold is somewhat incompatible with the signal you are feeding it.  If you look at the schematic for the CE-1, you will see that the sidechain that detects the envelope of the note in order to work the FET-gate uses a 3k3 and 470k resistor to set the gain of that sidechain.  Compare that to the sidechain of any envelope-controlled filter and you will see remarkable similarity in design, even though component vales will be a little different.  The goal is to have a smooth fadeout which takes place when the S/N ratio starts to get critical.  If you reduce the gain of the sidechain, then the FET will turn off "sooner".  You'll hear the chorus and vibrato sound as long as the signal is strong enough, but you may lose the tail of your note.  To increase the duration of that "tail", you'll want to increase C42 from .047 to something a little larger, though probably not as large as 1uf.  To reduce the gain, you can either decrease R75 from 470k to perhaps 430k or 390k, or you can increase R72 from 3k3 to something larger, like 3k9.  Dropping 470k down to 390k gets you a sidechain gain of 119 instead of 143.  Increasing 3k3 to 3k9 gets you a gain of 121.  It may not take much gain change to produce the needed fadeout change.

[fuzzboy]

Mark,
Thanks so much for the info. I borrowed another one from a friend, to compare, and it doesn't have the problem.
I'll check the resistors mentioned and make sure they're good. Any other ideas?

I'll let you know how it goes.

Thanks again.
Paul

[Mark Hammer]

The only other idea that occurs to me is that the trimpot that balances the two complementary outputs on the MN3002 is miss-set or has drifted.  One of the easons for using a device that has two parallel paths is that the clock signals each receives are opposite phase.  When the two parallel paths are combined, the audio samples each has are slightly different, but the clock signals are perfectly opposite, so they cancel.  Like any sort of counter-phase cancellation, the better the level matching between the two sources, the better the cancellation.

This need not be a case of one OR the other.  It might be that re-adjustment of the trimpot, and some fine tweaking of the response of the noise-reduction system to *your* instrument/rig yields the best outcome.

As far as adjusting the noise of the delay chip, keep in mind that unless there is a strong enough audio input, the resistance of the gating FET will remain low, so as to shunt signal to ground.  What that means is that if you are attempting to adjust it by ear, while plugged into an amp, you will need to keep that resistance high so that all noise makes it to the output.  The most straigtforward way to do that would be to disable the FET by unsoldering its source pin from ground, making the path to ground high-resistance under all signal conditions.  This will let you hear all the niose the pedal is producing, without the masking effects of the instrument signal over top of it.  Once you are satisfied that the trimpot has nailed the sweet spot for noise cancellation, just resolder that FET pin.

Alternatively, a less invasive way is to measure noise directly as AC signal using a scope or sensitive meter at the wiper of the trimpot.  Since the gate is situated after that point in the circuit it will not attenuate/gate any noise fed to your measuring device, whether you are playing or not.

My buddy Tim, who makes the CE-1 clone that was reviewed in the March "Guitar Player", worked for a while to get the right combination of component values in that gating sidechain to keep any stuttering of the gate to a minimum.  We had considerable discussion about it, after a customer complained about what he called "distortion".  I don't remember what the exact values were, (and probably shouldn't tell even if I could remember), but he said it yielded some improvement in noise performance.  I should emphasize that these are not problems with the CE-1 in particular, but rather enduring issues that ocur with any gating system, no matter where it is applied.  It is always difficult to determine when a note is starting, ending, and past the point of reasonably sound quality.

[ericohman]

I got a vintage Boss CE1 today and just been playing around with it. Sounds awesome, can't remember last time I was this amazed by something between my guitar and amp

BUT, I found it a little bit noisy, though pretty much only noticeable when you let a chord ring out, you definately here the "splash wave" kind of noise...
I didn't spend that much time with the level input, in fact I think I was a bit on the low side..

Has anyone used this pedal back in the days? Is it normal that you hear the noise or has something gone wrong with the one I got over the years?

[birt]

i think the replies that have been posted in this topic years ago answer you question.

[nickbungus]

I'm going to bring an old post up from the past!!  Only 12 years Old!

Schematic in PDF

Perhaps Mark can help if he remembers (or any one else).

My clone is noisy all the time but I'm not using the right Jfets.  By trying different Jfets do you think I can reduce noise during idle time?  I think I've got J113's or J112's in.  I started with J201's but I think my batch of these is dodgey/cloned off eBay probably.   It sounded awful with the J201s's but as soon as I replaced them I got a lush chorus.  The only problem is, when I crank the volume you can really here the LFO doing it thing.  It isnt noticeable when playing.  Its probably my crappy build but I'm hoping theres a magic wand solution!

[Fender3D]

R66 and R67 act as the P90 trimmer does.
If you place a 22K/25K trimmer instead of those 2 resistors you can set the "sweet spot" for the FET used....

[nickbungus]

Thanks Federico

Are you saying swap out R66 for a trimmer and leave R67 going to ground or remove both for the trimmer?  I'm not 100% sure of the configuration.

[Fender3D]

Remove both resistors one trimmer pin to GND, the other to -14V, wiper to D13.
Setting the trimmer sets bias voltage for the jFET

[nickbungus]

Thanks again

I actually thought that is what you meant (I must be learning something!!)

Cheers, I will try that this weekend over a cerveza or 2 (+ )

[njkmonty]

mmbf5457

[Fender3D]

Cheers, I will try that this weekend over a cerveza or 2 (+ )

..Better try before drink (at least for me...)

Cheers

[nickbungus]

I've only got a 50k multiturn trimmer in stock at the moment.  Can I use it or should I just order one in?

[Fender3D]

It will work the same...
longer to find the sweet spot, but more accurate

[njkmonty]

I tried your suggestion on my builds , only had a 30k pot

on the original schematic there is a voltage reference at  the junction of the diode  and R66 and R67

http://www.freeinfosociety.com/media/images/1884.jpg

to me its either -3v  or -5v   my eyes cant tell.

obviously when a note plays the voltage increases,  so I assume this voltage  (used to calibrate the trimpot idea)  is set to -3v  or -5v

and that would be without an input while calibrating?

[nickbungus]

Great the forum is back!

I tried the 50k trimmer but it made no difference at all.  Couldnt get it to gate whatsoever.  Any suggestions peeps?

[Fender3D]

I tried your suggestion on my builds , only had a 30k pot

on the original schematic there is a voltage reference at  the junction of the diode  and R66 and R67

http://www.freeinfosociety.com/media/images/1884.jpg

to me its either -3v  or -5v   my eyes cant tell.

obviously when a note plays the voltage increases,  so I assume this voltage  (used to calibrate the trimpot idea)  is set to -3v  or -5v

and that would be without an input while calibrating?

Voltages on the schematic assume you're checking a Boss card, I mean they selected the parts used there, and, unless you know how they made the selection or you use factory approved replacements, those voltages are just a reference.

Q12 acts the same as the FETs on a P90 phaser.
Correct bias voltage is not enough, you should use FETs correctly working with the voltage range applied.

About the setting...
I would short the input and look for the point where the gate starts and silences the hiss.
Just check the huge gain on IC3, or stray oscillation, does not engage the gate...

[nickbungus]

Ahh.  This seems interesting and I feel like I'm about to learn something

Correct bias voltage is not enough, you should use FETs correctly working with the voltage range applied.

Going back to my earlier post when I said I first tried J201's and it sounded like 's%^t'.  Perhaps they were working but the gate was doing its thing without being properly biased.  I will play tonight, but before I do that what property of the jfet am I interesting in (so I can check my datasheets and fet tester)?

[Fender3D]

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