EQD Space Spiral/Dark Rift Delay LFO

[lukegalea]

Hi - I'm trying to understand better how the modulation on the EQD Space Spiral/Dark Rift Delay works.

Basically I think that the LFO provides a voltage at the other end such that the current draw from Pin 6 decreases at certain peaks across the LFO.
However when I measured the LFO with my oscilloscope with the Depth turned all the way up I got a square wave from 0V to 5V. What happens at 5V? i.e. Wouldn't a current flow into Pin 6 change things since current is supposed to flow out of Pin 6? Can someone confirm these readings please?

Thanks!

 

[Chuck D. Bones]

What is the SHAPE control setting? Where are you probing the LFO, at pin 2 of the DEPTH pot? Different places yield different waveforms.

Current always flows out of IC2 pin 6. R21, R32 & the DEPTH pot form a voltage divider. A small amount of the LFO signal present at IC5-8 ends up at the top end of R21 (node labeled LFO) which modulates the current flowing out of IC2-6.

BTW, this doesn't sound like a Troubleshooting question. We have a General Questions forum for, well, general questions.

 

[lukegalea]

What is the SHAPE control setting? Where are you probing the LFO, at pin 2 of the DEPTH pot? Different places yield different waveforms.

Current always flows out of IC2 pin 6. R21, R32 & the DEPTH pot form a voltage divider. A small amount of the LFO signal present at IC5-8 ends up at the top end of R21 (node labeled LFO) which modulates the current flowing out of IC2-6.

BTW, this doesn't sound like a Troubleshooting question. We have a General Questions forum for, well, general questions.

Hi, I am on the square wave setting and I am probing Pin 2 of the Depth control. With Depth Pin 2 disconnected the square wave oscillates between 0V and 5V and when connecting it to the rest of the circuit is oscillates at a much lower peak to peak. Perhaps it's because of R21/1K.

Yes apologies for posting here. I posted in modifications before but no one replied, which is why I posted here then. I'll restart another thread then?

 

[Chuck D. Bones]

Your measurements sound about right.

No need to start a new thread, but next time please pick the right forum. Unless you're asking about a mod, please post in General Questions. Participation is voluntary so sometimes you have to be patient. Some posts never get answered, that's just the way it is.

Did I answer your questions?

 

[lukegalea]

So far yes - however I'm still having issues when trying to integrate the Tone God Taptation Kit with the Dark Rift Delay (at this point this question is OT however). Basically I'm trying to use an MCP41100 instead of the 50K time knob and 1K (R20) but the modulation is not working as it was before. With the depth control past noon, the LFO leaks into the signal.

 

[Chuck D. Bones]

OK, so this is a modification-related question.

You either need to keep R20 or ensure that the resistor inside the MCP41100 never gets below 1K. That LFO leak is the PT2399 malfunctioning when the VCO pin current is too high. I don't know anything about how the MCP41100 might interact with the PT2399.

You ever consider doing this with an FV-1 or Daisy (Terrarium) instead? The PT2399 is cheap, but its performance is limited.

 

[lukegalea]

OK, so this is a modification-related question.

Yes apologies about that once again.

You either need to keep R20 or ensure that the resistor inside the MCP41100 never gets below 1K.

My LFO leak issue is happening at all Time settings however so I doubt that the 1K is the issue? And yes - I monitored the LFO waveform (Depth Control Pin 2) and compared to the original design, the Vpp is able to go much higher.

I don't know anything about how the MCP41100 might interact with the PT2399.

This seems to be the black box that I'm trying to understand. Maybe I just have to understand that the MCP41100 does not work as an ideal rheostat? Btw just in case anyone is looking, the Bontempo Tap Tempo Kit seems to offer a more flexible solution with more modulation options already in-built. I just tried to take on the challenge of keeping the same modulation from the original kit.

You ever consider doing this with an FV-1 or Daisy (Terrarium) instead? The PT2399 is cheap, but its performance is limited.

I wish to take on FV-1 builds eventually yes