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PostPosted: Wed Sep 13, 2017 8:37 am 
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Location: Rochester, NY
A friend sent me his CMATMODS Tremoglo (product page) and asked for some help modding it. I emailed the designer, but haven't gotten a response back. (Not that I expected one, necessarily.)

What he'd like me to do is make it more useable in the lower depth settings. He'd like finer control of the subtle settings, but he'd also like it to go even more subtle, approaching or reaching no effect at all as the depth knob is turned down to zero. I don't have a schematic, but based on the attached photo, I figure the circuit is not overly complicated, and maybe one of you guys can help me figure out if this is possible. Here are two things I am thinking of trying. Do you think I'm on the right track?

1. Replace B250k depth pot with A250k to give finer control and slower increase to depth as it is turned up.

2. Check resistance of depth pot turned fully CCW; if not zero, determine if one of the nearby resistors is connected in a way that increases the lowest value.

Thoughts appreciated!

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PostPosted: Wed Sep 13, 2017 10:43 am 
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It looks like an EA tremolo circuit. It should have zero effect with the depth turned all the way down. Does it not?

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PostPosted: Wed Sep 13, 2017 11:26 am 
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It looks like the original EA circuit had a 68K from depth pot lug 1 to ground as a limiting resistor (which looks like is present directly above lug 1 of the depth pot in your photo). Try just jumping that resistor to get zero effect with the depth off.

The BYOC trem grounds the depth pot as described above. The BYOC trem also uses a 1 meg pot for the depth - I don't know if this would result in a wider range or not. But I do like your idea of changing the pot to an audio taper.

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PostPosted: Wed Sep 13, 2017 11:38 am 
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Morgan wrote:
It looks like the original EA circuit had a 68K from depth pot lug 1 to ground as a limiting resistor (which looks like is present directly above lug 1 of the depth pot in your photo). Try just jumping that resistor to get zero effect with the depth off.

The BYOC trem grounds the depth pot as described above. The BYOC trem also uses a 1 meg pot for the depth - I don't know if this would result in a wider range or not. But I do like your idea of changing the pot to an audio taper.

Very helpful stuff as usual, Morgan—thanks. I'll look into this later on and report back.

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PostPosted: Wed Sep 13, 2017 8:17 pm 
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Replacing that resistor (it was a 56k, actually) with a jumper did the trick! Thanks again.

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PostPosted: Thu Sep 14, 2017 8:29 am 
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Also, got an email back from Chad at CMAT last night. He was more than willing to help out but had a family member in the hospital that caused a delay in response. So great to find people in the community who are generous!

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