EH Microsynth filter mod

[StephenGiles]

A Happy New Year to everyone!

Sorry Mark, I should have started a new thread rather than crashing yours!!

I'm looking at the EH Microsynth drawing dated September 26 1996.

Still thinking: What if the peak follower output at junction of D3 and pin 6 of IC5B, which the circuit states falls between 0v and -7v depending on signal, is connected via Rx to one side of a 10k pot - Rz, and the voltage at the wiper of the Start Frequency to the other side via Ry with its wiper connected to R93 as shown in the attached circuit? The Start Frequency pot is also connected to 0v and -V so this should not present any problem.

Depending on the setting of Rz, could this make the initial peak of the filter sweep follow input level?

https://www.dropbox.com/s/fc2n6chetom01wt/Microsynth%20mod.pdf?dl=0

https://www.dropbox.com/s/cvdkpygav2bj9v6/Msynth1.pdf?dl=0

https://www.dropbox.com/s/6mhemd9vrbzwmka/Msynth2.pdf?dl=0

[StephenGiles]

Any offers? I don't have a Microsynth, and no plans to build one.

[StephenGiles]

I'm informed that it's worth trying.

[Rob Strand]

Depending on the setting of Rz, could this make the initial peak of the filter sweep follow input level?

An interesting point is biasing "post cap" means the cap will fully discharge and there will be a delay before it gets to the threshold.  Pre-biasing the cap, say via a diode, avoids the delay.    Don't know if it makes a noticeable difference.   The Boss CS3 detector biases the cap whereas some of the other detectors bias post cap.

I don't have a Microsynth, and no plans to build one.

I had some plans to do some VSTs of those complicated EH pedals.   Those projects have got put so far back on the backburner I can no longer see the flame;  I don't even know if the flame has gone out  .

[StephenGiles]

Depending on the setting of Rz, could this make the initial peak of the filter sweep follow input level?

An interesting point is biasing "post cap" means the cap will fully discharge and there will be a delay before it gets to the threshold.  Pre-biasing the cap, say via a diode, avoids the delay.    Don't know if it makes a noticeable difference.   The Boss CS3 detector biases the cap whereas some of the other detectors bias post cap.

I don't have a Microsynth, and no plans to build one.

I had some plans to do some VSTs of those complicated EH pedals.   Those projects have got put so far back on the backburner I can no longer see the flame;  I don't even know if the flame has gone out  .

Aha that reminds me of a Johnny Coppin song!!

https://www.youtube.com/watch?v=CAm6VfR05zQ

Listen to the drummer Trevor Foster - great sound!

[Mark Hammer]

The one I had in my possession for repair is now gone back to its owner, so I can't try the mod out.

[StephenGiles]

Such is life Mark, I'm waiting for our Sainsbury's home delivery which will take a couple of hours out of the afternoon, so just perused the schematics again and came to the conclusion that I would need to build at least 50% of a microsynth to properly test my mod. I'm hoping someone might take this up!

[Kevin Mitchell]

I've got a couple of Micro Synthesizers on my bench. I'll try these mods once I fix em' up - should get back into it this week.

[puppiesonacid]

Good morning!

Stephen,

I'm willing to give the mods a shot! i cant access the drop box links for some reason. can you pm me or email me directly? anthonybuckalew@hotmail.com