*best* LDR for Mutron III / Neutron circuit

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Re: *best* LDR for Mutron III / Neutron circuit

Postby digi2t » 02 Oct 2014, 11:20

Here is my tutorial for rolling your own Vactrol for the Mutron. I used a clear bright white LED, and two Waitrony KE-10720 LDR's.


The only thing I recommend is that you match the LDR's. I took a piece of wood, drilled two holes at the lead spacing of the LDR, and set it in a vice, underneath a light source that I could control the intensity. Pop an LDR into the jig, ensuring that it's sitting flat against the wood, and pointing directly at your light source. Connect you DMM to the LDR leads. Set your light source to an intensity where you get somewhere in the neighbourhood of a 10K reading from the LDR, it doesn't have to be exact. Write the reading down. Now, pull that LDR out, and insert another one in it's place. Connect the DMM, and take a reading. Compare the reading to the first one.

Keep going, until you get two LDR's that are within 100, to 200 ohms of each other. The Waitrony's are dirt cheap, so buying 10 or 20 of them won't break your bank. Definitely cheaper than VTL's. You'll be able to match up several sets.

No matter how many times I cut it, it`s STILL too short!

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aishabag23 (14 Mar 2017, 14:50)
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Re: *best* LDR for Mutron III / Neutron circuit

Postby rrroo » 14 Mar 2017, 10:23

I built the madbean version of this pedal. made my own LED/LDR. everything seemed to work in UP mode but not in DOWN mode. I found out that the bias voltage at op amp, defined by R18 and R19 is not optimal. if you replace these with a trimmer working as a voltage divider, you can dial in just the right filter sounds and the choise of LED/LDR is not that crucial.

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