Carl Martin - Contour & Boost  [traced]

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crazyabe
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Post by crazyabe »

Hi, I've been an occasional observer of the forum and I thought I would share this here since I did not see any information on this pedal.

So far, I've managed to trace all the components but I'm not sure if the traces are 100% correct.
I'm a noob so be gentle and let me know if I made any mistakes.

Oh by the way, this is a non-working Carl Martin Contour & Boost. It's output signal is barely audible to none. I'm trying to figure out what's wrong with it.
Using the audio probe, the signal dies out going into PIN 5 of the left IC. Barely anything comes out of PIN 7. Is this an IC failure? Again, I don't know what I'm doing :)
+12V are supplies to PIN 4 and -12V to PIN 11.
This image is horizontally flipped so that the circuit would look like you are looking in through the top with the components.
This image is horizontally flipped so that the circuit would look like you are looking in through the top with the components.
2.JPG
3.png
4.png
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Intripped
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Post by Intripped »

IMO if supply voltage is ok on pins 4 and 11 then you can reasonably be sure about the faulty IC.

LM837 should be equivalent, if you don't find the exact part.
probably you can also use TL074 and other quad op-amps, but i'm not 100% sure, so you'd better ask here
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crazyabe
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Post by crazyabe »

Thanks! I did order couple MC33079 but haven't arrived yet. Meanwhile, I've tried TL074 and it worked just as it should.
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loylo
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Post by loylo »

Feeling bored at work, I tried to trace the circuit. I think it may be 100% accurate, according to your pics, crazyabe. :D

Here it is:
Image

It's a nice and clever circuit (like all Carl Martin products) based on Sallen-Key filters topology.
http://en.wikipedia.org/wiki/Sallen%E2% ... y_topology

[EDIT] Forgot to mention on my schematic that both opamps are MC33079.
I will add this information soon.
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loylo
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Post by loylo »

As I can't post direct fullsize schematic via imageshack, here it is directly on freestompboxes!
Carl Martin Contour & Boost schematic
Carl Martin Contour & Boost schematic
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Bill_Mountain
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Post by Bill_Mountain »

I had really high hopes for this pedal with my bass but I kept overdriving it. Maybe mine was busted but I just assumed it had a ton of headroom because of the AC plug. It looks like there is a big boost at the input. That may have been my problem.

Thanks!
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