Planning on building some stereo devices

[markseo]

Hi,

I am planning on building some stereo devices to use both with my synths and when mixing, so I could send some stems from my DAW to get some nice hardware EFX. I have read a lot about how different stereo pedals work, where some are mono-in/stereo-out, some have a splitter before the actual effect, etc. For my personal purposes, I am willing to build an actual stereo-in/stereo-out device, but I have some doubts about how to get on with this project...

I know i will need to build two circuits, one per channel, my questions are more about power and controlling both circuits.

Is it mandatory to use double gang pots in order to control both circuits at the same time? Why would I need those if both circuits need the same resistance at their respective controls? I thought double gang pots were for situations where you needed to raise and lower resistence of two different parameters at the same time. If on the contrary, I can use standard pots, I would just solder the pot's legs to both pcb connections, right?

Regarding power, I have built some double and triple pedals that all shared the same power just by soldering their respective power lugs to the DC conector. This would work in the same manner? The + and - from both PCBs would go to the + and - leg of one single DC connector?

I am thinking about maybe avoiding putting a switch alltogether as this will be used more as studio rack equipment, I am sure this would make things a bit easier as I wont have to solder the true bypass circuit, and will save on switches, LEDs, etc... But any reason for adding a switch? I have read that I would actually need a 4pdt switch, which just seems to overcomplicate everything.

In regards to the actual effects I am thinking about... I was looking into building some modulation (probably a Ceaser or Cepheid Chorus and either a Pitch Witch or a Low Tide Modulator), I have read these should share the same LFO, is this mandatory? I would rather try and deviate as little as possible from the actual PCBs and schematics. I am also looking into building a Hydra Delay, once again, would I need to have any sharing section within the circuits or I can just build two separate circuits and just have them share all the controls, even the switches? And lastly, it would be amazing building some sort of tube or some sort of crunchy saturator, in case I decided to go with something based around tubes, same questions apply: Two independent circuits sharing controls and power? Or I would need to do something specific related with biasing, matching tubes/diodes/transistors, etc... ?

I am not looking into creating a perfect and amazing audio processor, I already have that in the box, but more of a nice and enjoyable manipulator that can add character, playabilty and some noise and crunchiness to my mixes and individual tracks, so not looking for the most pristine and industrially correct way of doing it. Just want to have some fun.

Oh! And finally, about levels... I don't have a reamp box, though I could build a stereo one quite easily from what I have seen, but I have also seen that most of the times, as long as you send low levels into the pedals and then use DI from the pedals back into the interface, nothing wrong should happen. Should I modify anything inside the circuits in order to make them work with line levels in and out? I do have DI for entering my interface, and have used pedals with synths many times and, by just lowering their volume they work as expected, not sure about outputting audio from my DAW though.

So any info, insights, links, or disclaimers are muuuuch appreciated

Thanks in advance

 

[Feral Feline]

...Is it mandatory to use double gang pots in order to control both circuits at the same time? Why would I need those if both circuits need the same resistance at their respective controls? I thought double gang pots were for situations where you needed to raise and lower resistence of two different parameters at the same time. If on the contrary, I can use standard pots, I would just solder the pot's legs to both pcb connections, right?
...

I worked briefly at a car dealership and a few times after maintenance a car was delivered to the wrong customer because the alarm/starter/key-fob operated on the same frequency as another customer's car — so the delivery-driver goes into the parking lot, clicks on the remote to find the car, but doesn't check the VIN and delivers the wrong car. There's only so many frequencies available to be used. Same thing for garage-door remotes etc. It's rare for two remotes to wind up within such close proximity to each other, but it does happen.

Imagine you have a wireless gas pedal in your car, sensors read where in the travel the pedal is and it sends out a small radio signal to the engine to increase or decrease the gas input.

Now imagine your neighbour has the same car, same transponder operating on the same frequency; if you both leave your driveways at the same time then when you press on the gas you'll be goosing the gas "pedal" of your neighbour's car and vice versa.



Crosstown traffic...
Hooking up two PCBs' gain-controls, for instance, to one single-gang pot is going to cause interference between the two circuits much as sharing frequencies between the two cars is going to crash one or both of them.

You either need
the dual-gang pot so that one knob controls both circuits,
or
you wire up single-gang individual pots to each control for independent adjustment, say you want the left channel to have more gain than the right for some reason.


Power Up
You should be able to use star-grounding/power as you suggested.


Switcheroos
A 4PDT is not overcomplicating things. A 4PDT toggle bypass would be a good idea IMO — better to have the capability and not use it than not have it when needed, but only you can answer whether you really need it. Switch up, it's on, down it's off — no LED needed.
Break things down into smaller chunks:
Left-Channel Circuit in the first 2 poles of the switch, the Right-Channel Circuit using the last two poles of the switch.

SHARE & SHARE ALIKE: Same thing for sharing switches in the functioning of the pedal as for the dual-gangs. If one circuit board requires a DPDT toggle, then you either use a 4PDT wired to L & R boards so you can turn on/off a function to both boards at the same time, or you go independent DPDT-toggles for each board so you can, for example in a delay, have dotted eighths in the left channel against the quarter-repeats in the right channel.


LFO MoFo
Again, only you can decide if syncing the LFO's together is important or not. No need if you don't mind the flanger in the left channel rising fast while the right channel's flange is dropping slowly — that could sound incredibly cool.
If you want things to work together at the same speed/direction, then you'll need to sync the LFOs.
A switch to couple/uncouple the LFOs would be bonus-points, have the best of both worlds.


LEVEL PLAYING FIELD
I remember my friend sending some pedals through his amp's FX loop... boy did it sound bad! Wrong levels, distortion (bad kind), squeeling — at the time, neither of us knew anything about level matching let alone impedance. His loop was meant only for line-level rack effects.
There's a reason for the Kleinulator effects-loop buffer, and for transfer-boxes such as the Radial Voco-loco that let guitar-level effects be used with mic-level signals or line-level...
Impedance Levels and Gain Levels need to be matched up!
Hence Radial's and other companies' re-amper devices. Nonetheless, you may be able to get by without one doing as you suggested.


DRIFTING AWAY
Bear in mind that due to manufacturing tolerances drifting, a Left Channel may sound different from a Right Channel. If a component type has 20% tolerance-drift, then your left channel could have a cap that's 0.8µF and the right channel has a cap that's 1.2µF when you really want them to both have 1µF so the channels sound the same. How much do you need each channel to sound the same? Do you have the time to sort through all the components and match channel for channel? Do you have the test equipment to do so? How close do they need to be matched to sound alike to the naked ear? What's matched on the oscilloscope may be overkill for the human ear.

Personally, I'd use 1% metal-film resistors and not worry about matching them up (unless for a Green Ringer or something like that), but I'd match up the caps as closely as possible, to at least 5% between channels for time-based things (modulation, delay, reverb).
For gain-based things like fuzz, I wouldn't worry about matching them up at all.

 

[markseo]

Ooh! Thank so much for such a great answer!!! This is all amazing info! I think I am totally going to get on with this Time to do some more research and maybe start buying some pcbs!

 

[dvdkmlr]

Sorry to revive such an old thread, but I used these tips to build my first stereo pedal. Ultimately it worked out great--I built a stereo Shika Fuzz with the 4pdt switch as suggested and it's super rad. I'm planning to build another (because the first build was, admittedly, a bit sloppy) and I really wish there was a way to include a LED. Unfortunately 5pdt switches appear to be near-impossible to find and, when they can be found, cost an arm and a leg. Is there any affordable way to incorporate an LED into this type of setup that doesn't require two separate switches?

 

[Erik S]

Sorry to revive such an old thread, but I used these tips to build my first stereo pedal. Ultimately it worked out great--I built a stereo Shika Fuzz with the 4pdt switch as suggested and it's super rad. I'm planning to build another (because the first build was, admittedly, a bit sloppy) and I really wish there was a way to include a LED. Unfortunately 5pdt switches appear to be near-impossible to find and, when they can be found, cost an arm and a leg. Is there any affordable way to incorporate an LED into this type of setup that doesn't require two separate switches?

No idea on the LED question, but I’d definitely like to see a build report on that double-Shika…

 

[dvdkmlr]

Working on the rebuild right now, I'll post it when I finish!

 

[Bricksnbeatles]

4pdt with millennium bypass