Boss CE-1 Chorus Ensemble

[TriSonics]

The original Boss CE-1 appears to have a noise gate built into it.
I am not a professional electronics person and basically build pedals as a kind of hobby.
Would anyone be able to point me in the right direction to modify a component(s) to cut down the shut off threshold that has been preset in the pedal? It cuts off too soon for my liking. It's fine when playing at a higher volume but when playing at low volume the right hand channel tends to not respond too well until the guitar volume is a little louder than I would like to play at that particular time.
The schematic for the pedal is here:
http://www.freeinfosociety.com/elect...es/bossce1.jpg
I would appreciate any help.
Thank you.
Mark.

[Ray Ivers]

Mark,

Replacing R73 with a 1M trimmer should allow you to vary the RMS level detector's (IC3) output to the gate of Q12, which looks like the gating device. You could also try just adjusting VR01 to raise signal level above the present gating threshold, but you'll probably get clipping if it's turned up too high.

Ray

[TriSonics]

Thank you

Ray,
Thank you for your advice. I appreciate it. I will have a look at this.
Regards,
Mark.

[Enzo]

Or remove Q12 and have no gating at all. Ther is an experoment that is easy to try. or is the chorus circuit too noisy for that?

[TriSonics]

Q12

Hi Enzo,
Thanks for your reply.
Well I was told that chorus would be noisy without the noise gate.
It might be worth a try to see if it is OK with Q12 removed.
Is it just a case of removing Q12 or would I have to link anything out on the board once it was removed? I am OK at soldering as I am an electrician but electronics theory is a little over my head. I tend to have to work on instruction. I am sorry for the amateurish questions and answers.
Thanks very much for your help though.
Regards.

[TriSonics]

Aha!

Aha! I see. Removal of Q12 will take out the noise gate completely. No need for any linking out etc.
Thanks Enzo. I will check it out and see how much noise is generated by it's removal.

[TriSonics]

Other mods

Has anyone on this bulletin board made any other type of mod to a Boss CE-1 that has improved the tone sucking that this pedal appears to have?

[delb]

CE-1 vintage chorus mod for tone loss

I just scored one of these and discovered 2 things that can be done, one seems more desirable, 1st mod is to replace the 50k volume pot with a500k pot. these pedals were made for keybord, not guitar, thus the signal loss, also you can replace R-11 which is a 470k ohm resistor( i have to check on that, and to find out the correct value, i think you go to 220 to 320, not sure if it is 220ohm or 220k, i will find out) anyway that is supposed to solve the early clipping issue with the volume input!!! Now modding a vintage and valuable pedal such as this could get you in trouble if you ever wanted to sell it, be sure and save all original parts. Here is something that may be better and easier, just get yourself a pedal looper, it has 2 inputs and 2 outputs (4 in all) and a TPDT footswitch, route the CE-1 thru it and voila true bypass, Keeley electronics sells a nice one for 85$, you could make one, all the parts can be found at: Pedal Parts Plus.com, hope this helps, these are the best chorus you can find!!! THE RESISTOR IS R-11 EASY TO FIND ON THE BOARD OF THE PEDAL, THE VALUE IS 470K STEP IT DOWN, OR JUST DO THE VOLUME POT CHANGE, VERY EASY, AND I STRONGLY SUGGEST THE LOOPER BOX. LATER

[TriSonics]

delb,
Thanks for your reply.
Interesting info.
I haven't, to this day, modified my CE-1 although I still plan to.
I doubt I would ever sell it but of course you are right about holding on to the parts.
Let me know how you get on with yours as you mod it.

Regards,
Mark.

[Mark Hammer]

The CE-1 was really targetted at keyboards, as replacement for a Leslie speaker. Since the keyboard would have a) a hotter output than guitar, and b) a lower output impedance than guitar, the Level pot used to adjust sensitivity is 50k; a value unlikely to load down a keyboard, but wreak havoc with a guitar signal.

A buddy of mine makes the Retro-Sonic CE-1 clone, and has garnered good reviews of it. During development, he found that "unloading" the guitar by means of simply replacing the 50k pot with a higher-value one conserved too much signal and introduced some distortion as a result. Consequently, while he kept the higher-value Level pot, other adjustments were made to the gain structure throughout, such that: a) no clipping occurred, and b) level balance was maintained when using a true bypass scheme.

So, if you do opt for a higher value Level pot, you will likely need to get used to setting it more modestly than you had in past, unless you make other adjustments.

The built-in gate was Roland's attempt to get away without using companding. Normally, companding would make clock-noise produced by the delay portion inaudible during silent parts. By using a gate, Roland essentially cuts out the delay signal when you're not playing so that any contributions of the delay section to hiss, whine, etc., simply disappear.

There are two approaches to having a more suitable decay in the gating action (and "suitable" decay is the eternal challenger to the functioning of ANY gate, no matter where applied). One is, as Ray already noted, to increase the gain of IC3 by altering R73, so that there is simply "more" signal to drive Q12 with. Note, however, that D11 sits on the output of that op-amp, and imposes a kind of "one-drink minimum" on any signal feeding the gate of Q12. That minimum will be a signal level of at least a half volt. With more gain in IC3, it should be easier to meet that minimum requirement, but what happens as the note tails off? No matter how large the initial transient peak was, the note WILL eventually fall below that 500mv minimum and that may be where your issues lie.

Which leads to a second strategy to have a more natural or graceful gating action: adjusting decay time. Both C41 and C42 serve to determine how long it takes for the accumulated charge that the input signal and envelope extractor provided to drain off. If they store more charge, then they continue to provide the gate to Q12 with a voltage that keeps the overall resistance of that FET low. If the charge they store is able to drain more slowly, then that also extends the decay of the gate.

Now here is where it gets weird and tricky to follow. Q12 is set up to be off when you play, and on when you stop playing. In conjunction with R48, it behaves like a volume pot that is turned way down when you stop playing, and turned way up when you start. That's why you have R66/67 and D13. They provide a constant negative voltage that the guitar envelope works against. If guitar<bias, then Q12=on. If guitar>bias, then Q12=off.

So, if you could get the guitar envelope to stick around a bit longer, then it would fight the good fight against that negative bias and keep the FET off a bit longer. One way to do this is to increase R68 to 470k or perhaps 680k. A second way is to increase C41 to perhaps .047uf.

Since it is a less invasive procedure to simply tack on a second parallel cap on the copper (solder trace) side to increase the overall value of C41, let's start with that. Get thyself a .01uf cap, find the solder pads where C41 is located, and simply solder the leads of the second cap to those pads. That's only .043uf, hypothetically, but it is still a roughly 30% increase. Give it a listen to see if it accomplishes what you want, and then we'll talk.

[delb]

boss Ce-1 mod

So i discovered that a 250k volume pot may work well and a change in C41 with the adding of A 0.1 cap across c41, however i am going to wait and see how the CE-1 works with my pedal board and a looper box in front, thanks to mark h.

[TriSonics]

Thanks for all this info. Great help.

[Blue]

I have one of these since buying it new around '82. I'm not as up on my electronics theory as I should be, but doesn't using another pedal between the guitar and the CE1, such as a compressor or delay for example, provide a buffer stage of sorts and eliminate the loading/sucking problem?

[Mark Hammer]

Yes, it should. The CE-1 was really constructed around the assumption that it would be used by people feeding a low-impedance output to it, such as what normally gets fed from a keyboard to a mixer.

Note, however, that simply providing a lower output impedance than input impedance can take on many different forms. So, the buffering effects of a device in line before the CE-1 would depend on that device's particulars. If it has an output impedance of 1k, then clearly you are in good shape. If that output impedance is on the order of 10k, then you still have anissue with the tone-sucking of the CE-1.

Note as well that many players like to use pedals with true bypass. So, even if the pedal just ahead of the CE-1 has suitable buffering, if you whip it out of circuit by stepping on a stompswitch, the CE-1 may well be facing a bigger load than it expects.

The bottom line is that you ARE correct in your assumptions that the CE-1 is capable of playing nice with other things, but one needs to assure those ideal circumstances are always made available to the CE-1 and not just sometimes. It may be totally unnecessary to adapt the input stage of the CE-1 in some cases, and necessary i other cases.

[Blue]

Thanks Mark, yes that's what I thought, I'll check the specs on the stompboxes I put between the guitar and the CE1... they're old Boss's and not true bypass so that's why I figuered I had at least a chance of one of them acting as an isolation stage, but as you say it depends on the output impedance, so I'll look that up...... again.... knew a long time ago... lol.. Used them this way for years with no problems, just curious now. Thanks again.