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Rate/Mod Rate LED for Polytrog

Started by wizestwizard, February 12, 2026, 11:50:33 PM

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wizestwizard

Hey guys, recently had a request from someone to add a rate LED to a Polytrog I build for them. I assume it will follow the "rate" pot if I put it in parallel with the LDR LEDs? If I do this, should I put it after all of the vactrol LEDs and then lower R42 to ~250R? This is a complex circuit compared to what I normally mod, so want to make sure I cover my butt before I start poking around in it!

If I wanted it to pulse with the "mod rate" pot, where would be the best place to tap into that voltage? Thanks!

madbean

Quote from: wizestwizard on February 12, 2026, 11:50:33 PMHey guys, recently had a request from someone to add a rate LED to a Polytrog I build for them. I assume it will follow the "rate" pot if I put it in parallel with the LDR LEDs? If I do this, should I put it after all of the vactrol LEDs and then lower R42 to ~250R? This is a complex circuit compared to what I normally mod, so want to make sure I cover my butt before I start poking around in it!

If I wanted it to pulse with the "mod rate" pot, where would be the best place to tap into that voltage? Thanks!

For the Rate pot you would put the LED in series with VC1-3_L, nt in parallel. Lowering R42 might compensate or prove unnecessary. For the Mod_Rate I'd try a 10k CLR and LED connected to pin7 of IC9_B first. Do it on a breadboard where you can easily disconnect the LED and see if it impacts performance.

These are just educated guesses.

wizestwizard

Thanks Brian! I'll test em out and see how it goes, I'll report back

wizestwizard

Quote from: madbean on February 13, 2026, 03:32:09 AM
Quote from: wizestwizard on February 12, 2026, 11:50:33 PMHey guys, recently had a request from someone to add a rate LED to a Polytrog I build for them. I assume it will follow the "rate" pot if I put it in parallel with the LDR LEDs? If I do this, should I put it after all of the vactrol LEDs and then lower R42 to ~250R? This is a complex circuit compared to what I normally mod, so want to make sure I cover my butt before I start poking around in it!

If I wanted it to pulse with the "mod rate" pot, where would be the best place to tap into that voltage? Thanks!

For the Rate pot you would put the LED in series with VC1-3_L, nt in parallel. Lowering R42 might compensate or prove unnecessary. For the Mod_Rate I'd try a 10k CLR and LED connected to pin7 of IC9_B first. Do it on a breadboard where you can easily disconnect the LED and see if it impacts performance.

These are just educated guesses.

This person is actually requesting another one built as a backup, and wants both the rate and mod rate slowed. They tested it against their own Polyphase and claim it's 2-3x faster as built, I didn't have one to test against but they sent recordings and it is indeed much faster even at minimum. The LFO section of this is pretty complex to my novice eyeballs, I'm going to see how the second one I built sounds stock but if I need to decrease the rates, is decreasing the pot values the way to go or would they need to be larger (which is not available probably, as they're both 1M lol)?