Planning my huge modular effect/synth board

[StephenGiles]

Very impressive, I take it you don't have any women or children getting in the way?

[frequencycentral]

How is feedback handled in modular synths? Would it make more sense to integrate multiple inputs to each module, or stick with the stompbox approach of having a dedicated feedback loop box?

I've got a few modular synths, built one of them myself. I'd liek to help, but I don't understand the question. What do you mean by "How is feedback handled in modular synths?"? Am I being a bit dim?

Modular synths usually do have multiple inputs for each module. Those that don't often have a few little 4 in / 1 out mixers that you can use to sum signals or control voltages.

[Taylor]

Very impressive, I take it you don't have any women or children getting in the way?

I've got a woman, but she's quite small, so it's rather easy to brush her out of the way.

I've got a few modular synths, built one of them myself. I'd liek to help, but I don't understand the question. What do you mean by "How is feedback handled in modular synths?"? Am I being a bit dim?

Modular synths usually do have multiple inputs for each module. Those that don't often have a few little 4 in / 1 out mixers that you can use to sum signals or control voltages.

Thanks, that answers my question.

I went back and reread some issues of DEVICE on Mark Hammer's site and I think I've got the idea with the power distribution and grounding.

Now, the question becomes: how do I modularize these individual effects? I made a thread on the topic of modularizing the Phase 90, which was largely about adding patch points for feeding back various stages to one another. But I want to go further.

Here's the Schaller tremolo schem, on which the Hearthrob trem I'm using is based. What I want is a to be able to modulate the speed of the LFO with another control source, like the Vanishing point. How would I do that? To clarify, I don't want to modulate the volume with the VP, I want the speed of the LFO to speed up or slow down at each stage of the VP. I'm thinking I should use the VP to control an LED which is aimed at an LDR that takes the place of the speed pot. Does that sound right?

With the Echo Base, I'd pretty much like to have all the parameters able to be modulated externally. The Mod Depth, Feedback, and level appear to be variable resistors, so I think I can use the same LDR approach mentioned above. What about the Mod Speed and Time pots?

[KorovaMilkBar]

I guess I'll explain all the modules I plan to have, so there won't be a need to suggest things I'm already doing. Stuff in red is aready built.

*Buffer/splitter - maybe 4 or 5 outputs
*Compressor
*Analog pitch shifter - this is my own design, based on the E&MM harmony generator. It will be rather huge itself, with volume sliders for 21 pitches, and highly patchable into itself. More on this later.
*Ring Stinger ring modulator (for dirty ring mod, also has lots of patchability, which will be cool for this project)
*2 passive diode ring modulators
*Frequency Analyzer ring mod (for clean ring mod)
*Analog sample rate reducer
*Heartthrob tremolo - was originally thinking the Tremulus Lune, but I had one already and found it to not be as versatile as its knobbage seemed to indicate. Listened to Hearthrob on John Lyons's site and I really like how smooth it is on slow speeds but nice and choppy on fast speeds.
*Phaser - don't know which one - any suggestions? I'd like something that sounds really thick at slow speeds, so Univibe for example doesn't work for me
*Vibrato - don't know which one. I want a true vibrato, ideally that can go really deep, like shifting an octave up and down. Don't know if such a project exists.
*2, maybe 3 Rebote delays with feedback loop send/return
*A digital delay of my own design
*A couple of feedback loops with limiters
*LFO
*Envelope follower
*Vanishing Point
*VCA/ADSR -this will be a synth design. The pitch shifter puts out a trigger signal, but I have no idea yet how usable it is. I realize that deriving a trigger and gate from a guitar (actually bass in my case) is going to be difficult.
*Spring reverb
*Mixer
*Possibly a Payback or 2 - I really want a looper with overdub capability but this doesn't seem doable in DIY

So, questions: Synth modules typically are working at higher levels than guitar signals and effects, right? So will the synth designs work with the quieter level that the stompbox circuits wil be outputting?

If i may ask... how did you build the ring stinger? any links to schematics?

[Taylor]

There's a whole project for it around here somewhere... a quick search should find it for you.

[Taylor]

Quick update for anyone interested (thumbnails, click to enlarge):





Yes, it is very messy in there, and I'm quite embarrassed, having seen the impeccable work that so many of you on this forum do. In my defense, the power wiring will soon get zip tied up and fastened down more neatly.

Looking at the front picture, starting at the top left, going to the right, there's
*an input with a booster and 4 buffered outputs,
*then a compressor/fundamental extractor for my upcoming pitch shifter/synth which will go next to it,
*Heartthrob trem
*Analog sample rate reducer
*modular phaser I designed - 12-stage Phase 90 - supposed to have patchable feedback paths from any stage to any other stage, but not working yet.
*Ring Stinger

*Then, second row:
*8-stage sequencer
*CMOS Aliaser

3rd row:
*Heartthrob trem #2
*Echo Base with switchable effects loop and control input for delay time
*MS20 filter
*Omnidrive
*Random Number Generator

4th row:
*spring reverb
*headphone amp
*mixer
*3-band EQ

Still a lot of stuff to do/fix here. Most of the modules that are installed work, but a couple either have some quirks or are currently not working at all.

This thing is a lot of fun. Patching the sequencer to control delay time, while the delay feedback gets ring modulated once more with each repeat, into spring reverb... awesome.

It's not even all that noisy considering it is mounted in a non-metal board and there is no shielding anywhere. Once I work out a nice way to shield it all, this will be a very nice piece of kit indeed.

I've been pondering having a couple of mini-amps inside, so I can plug directly into a pair of speakers for stereo fun. Then I started thinking about putting some speakers right in the case. Still pondering this. It would be kind of fun to be able to show up with just my bass and my suitcase and make insane noises. OTOH, not sure how it would go having speakers vibrating my electronics. Also pondered having some tube drive or a full tube amp inside, but tube circuits still scare me.

I'm moving in a couple of days, so I need to build the case fast. Plan to have some legs to hold the case in an angled upright position, and some sort of door to allow access to the springs of the reverb, so I can whomp them and clip gator clips to them and so forth.

[Mark Hammer]

Here's mine.  The chassis, unstuffed:  http://i414.photobucket.com/albums/pp228/Mark_Hammer/DSCF0790.jpg

...and stuffed with 2.5" x 4" modules:  http://i414.photobucket.com/albums/pp228/Mark_Hammer/DSCF0787.jpg

The 2.5 x 4" space limit imposes some constraints, but quite frankly, anything that needs a bigger space for the board is probably something I want to put in a self-contained chassis anyway.  That's why there is a splitter/mixer module with 1/4" jacks for interfacing to the outside world.  The option is always there to split a circuit up into two boards and stack them with spacers behind the faceplate.  Like you, I found the cost differential of mini phone jacks vs 1/4" jacks to be substantial when they start to get into the dozens.  Happily, the Canadian Radio Shack was clearing them out at 2 for 96 cents, so I bought....a lot.  DPDT toggles are also a lot cheaper than stompswitches and have the advantage of showing you their status simply which way they point.  Another source of savings.

Since the number of modules exceeds, and will certainly continue to exceed, the available space in the two chassis (24 slots in all), I prefer to use a physical modular approach as opposed to the single big box like you used.  That way, I can stick in what I like or upgrade to other things as new projects come about.  Also allows me to keep the patching less chaotic by sticking things that need to go together...together.

[Taylor]

Mark, thanks for that reply. I've seen those and they were a major source of inspiration for mine. Your thoughts are very much appreciated.

I'm also using DPDT's for switching, another great idea I stole from you. Since I'm not a gigging musician, and my music lends itself to slow fades rather than quick on/off switching, I don't need individual stomps for everything. I plan to add a floorboard which would house a few stomps and expression pedals that can be interfaced as needed.

The physically modular vs. big box was something I pondered for some time. My pitch shifter/synth has 21 slide pots, and after searching for quite awhile, I was unable to come up with an affordable way to cut slots in metal, so the decision was made to make the face plate out of another, more easily cut material. In making that choice, it became necessary structurally to keep the face plate a single piece.

Luckily, I'm not the type who uses endless new fuzz boxes. Also, because my "panel width" is not standardized, and I can stack PCBs on their edges, I'm able to get an effect into a space 1.5"x4". The whole panel is 20x30, so I could theoretically get 60 effects in here, way more than I'd ever need. In reality, some of my effects needed more space, so I'll probably be able to get about 30-40 modules.

The patching would indeed be neater if I could put things next to each other which get used together a lot. Perhaps if I ever build one of these again, some normalization would be useful, like this guy's DIY synth:

http://hem.bredband.net/bersyn/concept.htm

He's able to select common signal paths with thumbwheels; pretty slick. That goes on my "concept list" for my modular v2.0.