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New Development: Tri stereo chorus

Started by fair.child, January 10, 2023, 07:26:13 AM

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FYI there was an American company that made a Tri Stereo Chorus clone:

I have one, but have never ABed it against the TERC, which I also have


Quote from: SugarKeys on January 29, 2023, 11:34:04 PM
FYI there was an American company that made a Tri Stereo Chorus clone:

I have one, but have never ABed it against the TERC, which I also have

I heard about these guys. It's gotta be rack unit though to get that schmo lol


Quote from: fair.child on January 10, 2023, 10:55:55 PM
Quote from: madbean on January 10, 2023, 09:40:14 PM
Looks like the three chorus sections are identical so if you trace one you get them all. The vactrols are might be for the three intensity knobs if I'm guessing. Taking the output of the LFO to split it to the three clocks maybe?

That is correct. The chorus section looks like are the same with different calibration

those trimmers adjust the DC offset going into the BBDs and adjust the center frequency of the VCOs for the clock oscillators. Same as the TSC.
The optos are for the manual LFO for adjusting the frequency and to make it a sine wave oscillator. Also same as the TSC.


I'm just curious to know if any progress has been made on this?

I have a TERC and recently lost the left output.  I've been doing my best to chase the signal through each of the three "bucket paths" and all looks good, but one of the 4558's (U7) near the output has 7.5V on the B output (pin 7).  My gut tells me that one of the 5457's failed, but a schematic, or even that section of a schematic would be helpful before I feel compelled to pull up the board.

Fulltone hasn't bothered to respond, despite that this unit should still be under warranty.

EDIT:  Found the issue...U7 was bad.  Replaced it and it's all good now.  Still wouldn't mind a schematic if there's one out there though.  Thanks!


I'm glad yours is working now. I got busy with other stuff these days. After NAMM this year, things are going busier. I do have half-baked schematics but they aren't complete. Mike Fullerton was there at the NAMM show and he said he won't making TERC in the future.


Thanks, I'm glad to having it working again too but disappointed that Fulltone never responded.  I guess that the new manufacturing agreement with them probably also means that any warranty work is also out of the question.  I wonder what's going to happen to all those MN3007's he has?

Prior to fixing my TERC, I fixed my TC1210 which turned out to have a faulty BC547 AND a faulty 4013 on one of the Delay Cards.  The experience inspired me to attempt to reverse engineer the calibration process and redesign the card to work with a couple of mn3007 chips rather than the impossible to find mn3010's.  It's a work in progress, but could ultimately lead to recreating the 1210.