Moonshot Tremolo Gain

Quirkey

Quirkey

Active member
I've had a mostly working Moonshot Tremolo on my bench for a while now and though 'It Works' with the gain knob at max it is still quieter than unity. This might be normal (?) but seems weird with two op-amps in there. I'm guessing there's some R value I can tweak somewhere or maybe tweak the gain pot to give me more total output? Are there certain resistors I should check? Thanks for the help as always.
 
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The resistance of the LDR will have an effect on the amount of gain.

You could increase the value of R3, or the Gain pot, adjust the distance between the LED/LDR, or swap the LDR for one with resistance.
 
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Quirkey said:
I think it was the cheap LDR I got, but I ended up swapping the value of R3 for a 330K and that seemed to boost the gain a bunch.

Thanks!
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Hi Quirkey,

though it's been some time since your post. Did you manage to get the pedal working nicely? I've got the same low gain problem and I just ordered some new LDRs. I wonder if changing R3 to 330k might result in some distortion problems if you use pedals in front of it that raise the output (e.g. boost or overdrive)?

Best regards,
Mark
 
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howas said:
Hi Quirkey,

though it's been some time since your post. Did you manage to get the pedal working nicely? I've got the same low gain problem and I just ordered some new LDRs. I wonder if changing R3 to 330k might result in some distortion problems if you use pedals in front of it that raise the output (e.g. boost or overdrive)?

Best regards,
Mark
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I did get this working well but it's not on my board right now. I forget the value that i ended up swapping for but I think it was less than 330K.

Also one thing I remember is to make sure you test with the cover on/in darkness as these LDRs are very effected by ambient light.
 
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I just finished a moonshot build and I made a couple of changes to pot values as per mmsulia's review here:
https://www.pedalpcb.com/product/moonshot/
This involved changing the rate pot from a B100k to a C100k (which was perfect) and the volume pot from an B10k to an A10k which apparently didn't work out so well as the output is slightly below unity when the gain pot is all the way up.

Would changing the value of R3 as per this thread be a good idea?
Or should I swap the Gain pot for a B10k as per the build docs?
Or re-orient the LDR to face the LED as I saw suggested in another thread?

I've attached a photo in the next reply for reference, thanks.
 
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Vicious C said:
Yes, re-orient the LDR to face the LED. I even cover mine with electrical tape to keep the light out
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Well, that was not much fun. The LRD was a pain to desolder with the legs underneath and a curved surface. But...what a difference! Not only is it louder, the circuit sounds noticeably better - thicker tone and gobs of gain. With the depth turned off, it's actually a really nice sounding clean boost, didn't expect that! Thanks.
 
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zakco said:
I just finished a moonshot build and I made a couple of changes to pot values as per mmsulia's review here:
https://www.pedalpcb.com/product/moonshot/
This involved changing the rate pot from a B100k to a C100k (which was perfect) and the volume pot from an B10k to an A10k which apparently didn't work out so well as the output is slightly below unity when the gain pot is all the way up.

Would changing the value of R3 as per this thread be a good idea?
Or should I swap the Gain pot for a B10k as per the build docs?
Or re-orient the LDR to face the LED as I saw suggested in another thread?

I've attached a photo in the next reply for reference, thanks.
Click to expand...
For future reference, a 10k pot is a 10k pot, you did not change the pot values. What you did change was the pot taper, which basically means "where are the values distributed through the pot's travel". For a clarification check the graph on this page: https://eepower.com/resistor-guide/resistor-types/potentiometer-taper/#

A B-pot is linear, so 50% pot rotation is 50% value. A is logarithmic, so at 50% rotation you've only got 10% value, and it moves faster from there. C is reverse log, so at 50% you're at 90% value already, but you get finer control for the last 10% of the value.
 
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