Hi there, i'm building a modular synth at the moment & I've been coming across the following problem.
Some of the modules seem to interfere with other modules even when they are not patched together, Example:
lets say I have an oscillator patched straight to a mixer with no other modules connected to it, no modulation or cv control etc.... Now all the other modules like LFO, envelope generators or anything that generates rhythmic patterns or modulation( mainly with leds ) will interfere with the Oscillator pitch ( very slightly, like a light vibrato, depending on the rate of the other modules ) even thou, like I mentioned before not directly connected to the Oscillator!!
the only connection is: they are all connected through a bus that connects to a power supply.
I'm using bi polar Power supply 12+ 0 12- but not all modules need bi polar, some designs are 12v single rail.
I have tried another power supply but with no luck, still the same!
Everything else is working well, & I have done filtering caps on power rails for each module & I have checked all circuits?!
I have different oscillator designs, but this problem affects all of them.
I have been building circuits (mainly music stuff ) for some years now, but my knowledge is still limited when it comes to problems like this. I would very much appreciate some help & apologies for my English as it is my second language & sometimes I find it difficult to explain in writing
many thanx , Jackos

 

It has always been on my agenda to build my own modular synth but since I haven't yet I can only provide you with links for similar problems. There seems to be some inconstancy to what might be the cause of the bleeding...So you might want to check them out for yourself and see which may apply to your problem.

Oh and schematics wouldn't hurt.

http://electro-music.com/forum/topic-16769-0.html&postdays=0&postorder=asc&highlight=

http://electro-music.com/forum/topic-16482.html

https://www.muffwiggler.com/forum/viewtopic.php?p=1266616&sid=c2d764c71089fbc17ac17dfa97c59b3b

 

It has always been on my agenda to build my own modular synth but since I haven't yet I can only provide you with links for similar problems. There seems to be some inconstancy to what might be the cause of the bleeding...So you might want to check them out for yourself and see which may apply to your problem.

Oh and schematics wouldn't hurt.

http://electro-music.com/forum/topic-16769-0.html&postdays=0&postorder=asc&highlight=

http://electro-music.com/forum/topic-16482.html

https://www.muffwiggler.com/forum/viewtopic.php?p=1266616&sid=c2d764c71089fbc17ac17dfa97c59b3b

It has always been on my agenda to build my own modular synth but since I haven't yet I can only provide you with links for similar problems. There seems to be some inconstancy to what might be the cause of the bleeding...So you might want to check them out for yourself and see which may apply to your problem.

Oh and schematics wouldn't hurt.

http://electro-music.com/forum/topic-16769-0.html&postdays=0&postorder=asc&highlight=

http://electro-music.com/forum/topic-16482.html

https://www.muffwiggler.com/forum/viewtopic.php?p=1266616&sid=c2d764c71089fbc17ac17dfa97c59b3b

 

Hi there Sinus,
Thanx, for reply, Yes it makes sense to be some sort of bleeding ! some ground thing maybe? I did disconnect 1 by 1 against the Osc's but no luck!
thanx for the links will check it now!!
As for schematics... some are off the web like mofos ( music from outer space) etc.. others i modify to my needs, a section from here & there, some specially with cmos I've come up with some wierd cool things with intention for one thing & ended with few others :0)
do have loads of scribles ( schematics) but need to put it all into a clean form on paper before i can upload stuff ( all very messy at mo.
Very addictive this do DIY music circuits!!
Again, thanx for the reply & all the best
PS. going to dive into the links right now

 

Do you have a star (i.e. single point) ground system for the modules?

 

Do you have a star (i.e. single point) ground system for the modules?

Hi there Alec, thanx for reply
At the mo I'm working on a smaller case that take about 24 modules.
what I've done is, made a panel for the power supply input & from there it goes into a 12 socket bus strip (for 12 modules) & that is followed (chained to) another 12 socket bus strip on the other side of the case (in other words i'm connecting the bus strips in series!!
What i'm beginning to understand is ( i think?) I should not chain the 2 strips together, but run them in parallel to the one point on the power supply input panel ! is that what you are saying?
Again thanx for the reply, all the best.

Ps. at mo i'm finishing more modules, & will get back to the power rails. But let me know anyway, thanx.

 

It's because they're still "on." They're still connected to the power supply, so there's still a connection. That's always been a problem with modulars. Whereas a single synthesizer does not allow a circuit to be powered up that is not being used, the constant connection on modulars allows a pathway for the circuits not being used. They need to be disconnected when not in use. Better grounding may help. What type of casing are you using?

 

I should not chain the 2 strips together, but run them in parallel to the one point on the power supply input panel ! is that what you are saying?

Yes. Otherwise the modules pick up noise from each other's grounding paths.

 

It's because they're still "on." They're still connected to the power supply, so there's still a connection. That's always been a problem with modulars. Whereas a single synthesizer does not allow a circuit to be powered up that is not being used, the constant connection on modulars allows a pathway for the circuits not being used. They need to be disconnected when not in use. Better grounding may help. What type of casing are you using?

Hi there Floomdoggle,
Thanx for reply, I'm using a wooden case from an old organ. I don't understand what you mean about disconnecting the modules (panels)? Do you mean outside patching?
thanx, jackos

 

Yes. Otherwise the modules pick up noise from each other's grounding paths.

Hi there Alec, thanx for reply.
I'm going to try this & also try to separate modulation & gate generators etc... modules on different power bus rails from osc & audio signal paths. Will let you know how it goes soon once I finish a few modules I'm putting together at mo. thanx man!!