# Moonshot Tremolo LDR Led?



## BurntFingers (Aug 29, 2020)

The BOM shows a GL5516 LDR is recommended. They've got a wavelength response of 550nm, yet a red LED (in the BOM also) is 650-700nm, meaning the LDR will operate at about 60-70% efficiency. 

A green LED's wavelength is bang on 550nm, which matches the 5516 specs.

So, why not use the green? Is there something in the circuit that likes having an LDR not operating at 100%? Just what was on hand maybe?


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## Cybercow (Aug 29, 2020)

Suggest  you socket the LED and try each color to see what sounds best to you.


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## BurntFingers (Aug 29, 2020)

Well it's going to be part of a vactrol so I'd rather not guess at it. I was hoping the designer or someone with ldr knowledge could chime in and steer this ship.


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## Cybercow (Sep 1, 2020)

It's pretty much a safe bet to follow the BOM, regardless of the technical details of any specific component. I'm sure the designer has already undergone testing and is aware of the efficiency variation. I've built (rolled my own) Vactrols many times and have had no issues with builds where the LDR\LED combos do not match wavelengths perfectly. And with the GL5516 costing only 50¢, an LED only pennies and the tiny bit of heatshrink, it should be of little consequence to build two of them, each one with each color.

And for testing purposes, the Vactrol need not be fully assembled - as long as the two facing components are enshrouded in dark.





Still, if you prefer the greater efficiency, go with the green LED. However, the end result may not work precisely as the designer intended.
Good luck. Cheers!


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## zgrav (Sep 1, 2020)

Seems like the most effective range for LDRs in phasers is the dim-to-mid range for the light, so it is unlikely the lights are often dialed in for maximum brightness.


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## Travis (Oct 12, 2020)

Cybercow said:


> It's pretty much a safe bet to follow the BOM, regardless of the technical details of any specific component. I'm sure the designer has already undergone testing and is aware of the efficiency variation. I've built (rolled my own) Vactrols many times and have had no issues with builds where the LDR\LED combos do not match wavelengths perfectly. And with the GL5516 costing only 50¢, an LED only pennies and the tiny bit of heatshrink, it should be of little consequence to build two of them, each one with each color.
> 
> And for testing purposes, the Vactrol need not be fully assembled - as long as the two facing components are enshrouded in dark.
> 
> ...



Is it better to do this with Delegate Compressor build?


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## zgrav (Oct 12, 2020)

Interesting question.  I think the speed with which the LDR is able to raise and lower the resistance would be a significant factor for the Delegate/Warden.  I may try the VTL5C9 Vactrol that is used in the Madbean Wavelord for the Boneyard compressor build.  I would not suggest that for anyone wanting to create a "perfect" clone of another pedal, but the Boneyard is all about tweaking for better performance.


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## Cybercow (Oct 12, 2020)

RCZ said:


> Is it better to do this with Delegate Compressor build?


If you cannot locate the GL5516 LDR, SmallBear has an equivalent here: SmallBear LDR

Select the "8002" option from the drop-down list. It is a 500K (min) dark LDR, similar to what the Delegate Compressor calls for.


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## Cybercow (Oct 12, 2020)

zgrav said:


> Interesting question.  I think the speed with which the LDR is able to raise and lower the resistance would be a significant factor for the Delegate/Warden.  I may try the VTL5C9 Vactrol that is used in the Madbean Wavelord for the Boneyard compressor build.  I would not suggest that for anyone wanting to create a "perfect" clone of another pedal, but the Boneyard is all about tweaking for better performance.


Note that the VTLC59 Vactrol has a dark resistance of 50MΩ - much higher than the 500KΩ dark resistance of a GL5516 LDR. This chart may prove useful. I use it often to compare Vactrol values to LDR values to assist finding equivalent replacements.

But, the PedalPCB Delegate Compressor (Boneyard edition) schematic has yet to be released, so I'm unable to verify which LDR is called for.


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## Chuck D. Bones (Oct 14, 2020)

Boneyard uses the same Vactrol or LDR/LED combo as the "commercial" Delegate.  Which optos or LDR/LED will work best is very circuit dependent.  For example, there is a 2.2M resistor in parallel with the Delegate's LDR.  That means that once the LDR resistance gets up to 2.2M, it has very little influence on gain or compression beyond that resistance.  Similarly, once the LDR resistance gets below 20K in the Delegate, it's as low as it needs to go; anything beyond that is wasted, or worse.  Overdosing an LDR with light just makes the resistance go up slower when the LED turns off.  Forunately for the Delegate, the ATTACK & RELEASE controls limit the LED current and allow us to optimize the LDR response time.  The important LDR or opto parameters in a compressor are light resistance (at the appropriate LED current), dark resistance and how fast the LDR resistance goes up when the LED turns off.


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