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Old 3rd August 2007, 04:53 AM   #1
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Question Improving a Boss CE-1 Power Supply?

Hi,

First post here at diyAudio. Looking for help with a replication of the 70's Boss CE-1 chorus pedal, as I have only a fair knowledge of electronics. It seems like the only way to get that big, vintage tone is to either spend $350-500 for a beat-up unit off eBay or build it yourself.

Here's the only schematic I could find:

http://www.freeinfosociety.com/elect...iew.php?id=119

I realize there are many obstacles provided by this circuit, but for now I'm focusing on the power supply. Everything runs off +/- 13 volts and +/- 14 volts DC, at least I think that's what it says. I'm assuming I need to stick with those voltages too(might change the gain or headroom?).

If a faithful reproduction of the original tone is the goal, would it be best to seek out those obsolete(?) power transistors or can I replace them with something like voltage regulators?

I understand I have a lot to learn so absolutely any help is greatly greatly appreciated.

Thanks, Jake
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Old 3rd August 2007, 08:47 PM   #2
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Can you get the BBD device? As far as I know all makers of analog Bucket-Brigade delays have discontinued them. The power transistors in the power supply won't change the sound much (or at all). Without the BBD it won't work at all.
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Old 3rd August 2007, 10:57 PM   #3
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Yes I found those at Small Bear Electronics...

http://www.smallbearelec.com/Detail.bok?no=246
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Old 6th August 2007, 06:45 PM   #4
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I think I'll be able to get the right transistors from dalbani.co.uk. Do they have to be "matched" or will the circuit produce the proper voltages anyway?

Also, what can I use in place of the 05Z15A diode? I don't really understand what its purpose is.
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Old 7th August 2007, 01:31 AM   #5
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It's a 15V Zener diode, setting the output voltage of the regs. I see no need for matched transistors in this circuit.
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Old 7th August 2007, 08:42 AM   #6
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Have you looked at the newer Boss CE-2 schematic?

Tonepad.com is an excellent resource for this stuff. They also offer PCBs for cheap.

The CE-1 uses the MN3002, a 512 Stage chip, whereas the CE-2 uses the MN3007 or
MN3207 which offers 1024 stages for longer delays. (the MN3207 is basically the same
chip as the MN3002 but can be run as low as 3 volts, which would greatly reduce the
complexity of trying to clone the CE-1's powersupply.)

Also, check out the Small Clone Chorus, which uses much simpler clock than either
of the other two.

Of course you could also pick out the best features of the three and roll your own,
DYI style.
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Old 7th August 2007, 04:53 PM   #7
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Thanks for the replies. I've looked at the CE-2, Small Clone, Ibanez CS-9, and the Boss DC-series chorus pedals. I find it hard to describe what it is about the CE-1, but the others just can't get there tonally. Even the Retro-sonic Chorus Ensemble, which claims to be the only circuit that uses the original MN3002 chip, seems lacking to me.

I think a big part of what made the CE-1 so great was its funky input-loading thing. The input impedance seen with those vintage transistors and the optional Mic Preamp section changes the way the guitar interacts with it (frequency response, gain) in a pleasing way.

A few more questions:

For the 15V zener diode, will a 1/2 watt power rating and 200mW current rating suffice?

What would you guys recommend for the transformer as far as current?
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Old 8th August 2007, 04:10 AM   #8
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They apparently use a 34vct secondary to achieve 23.7v per leg after the bridge.
A substitute transformer might require some resistor tweeking.
Watch the 16v caps if you use a higher voltage transformer.

100 ma transformer ought to be plenty.
200mW diode should be ok.

Have you thought about using super regs to increase the PSRR to lower the noise?
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Old 8th August 2007, 01:03 PM   #9
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At first I wasn't sure I could find everything that the original power supply calls for. If I can get those obsolete transistors from Nikko Electronics, I think the best option is to try the original spec and see if I have a noise issue. Again, thanks for the help.
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