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I’m about to take on a dual Mini-Me build and was looking at a couple of things . . . .
- There is no protection diode in the circuit. Up examination of the PCB, R31 (47Ω) looks like a perfect spot to slip in a 1N5817 Schottky diode. I’m trying to decide if I should “tent” the 1N5817 in front of and with the 47Ω resistor – or just use the 1N5817 without (in place of) the 47Ω resistor. Thoughts?
- In this dual Mini-Me build, I want to be able to run each circuit independently of the other – OR – synchronize them by tying each CD4047 clock chip to the same LFO and depth controls. Initially, I was considering tapping into the two lines that run from the CD4047 clock chip to the BBD. But with closer examination, I think I can get an easier switching mechanism by using the junction of R29, C19 and P1 (Depth pot) lug #2 as the tap-in point for making and breaking the connection for the LFO & Depth controls synchronized to one, the other or independent. It would be cool if there was a tri-state stompswitch as a foot-activated feature, but I think a 2P3T or 4P3T toggle will suffice.
In any case, here is the modded schematic for your kind consideration and feedback with regard to synching two Mini-Me circuits.
Oh, and of course each circuit will employ Wilkie1’s excellent Depth mod.
The protection diode needs to have the cathode connected to the voltage source and the anode connected to the ground. R31 does not connect directly to ground. I don’t think that would work there. Would it be easier to connect the diode directly to the power jack? That would protect both circuits,
I agree that the P1 (Depth) lug 2 would be a good point to switch the LFO. I don’t know if there is enough current there to supply both circuits. Your test will confirm that.
I have not had good luck running 2 phaser circuits in series with separate LFOs. Unless synced, they will beat against each other. If you can get them to share one LFO, it might work. I think you may get a “hickup” when switching the LFO, but I don’t think you will hear a “pop” since you are not switching the audio path.
Curious to hear the result!
Tanks for the feedback Wilkie1 !
With regard to the protection diode, I’m employing a different protection scheme – with a 1N5817 Schottky diode ‘in-line’ with the power supply instead of using the GuitarPCB standard protection scheme of shunting a 1N4001 to ground for protection. I like the 1N5817 scheme better because research and experience has shown that the 1N5817 acts much faster in-line than a 1N4001 does when shunted. Also, the 1N5817 has a much lower Fvd than a 1N4001. I’ve basically taken the 1N5817 scheme from PedalPCB – where in all their circuits use that protection scheme as opposed to the shunted 1N4001. Also, the 1N5817 Schottky works very well with a 47µF cap for for exceptional filtering. A friend in the UK ran the two different schemes thru LTSpice and explained why the 1N5817 & 47µF cap solution was a superior solution to the shunted 1N4001 diode. And having such a diode on each circuit from the start will make it easier to separate the circuits for individual builds should the experiment be a failure. At the very least, I will have two Mini-Me circuits to box up. 🙂
And the question about enough current being on hand for just one of the LFOs being able to drive both clock drivers, I’m thinking I could lower the value of R26 (180K Ω) to bump up the current a bit. I suspect a 120K value at R26 would suffice. But as you said, testing will expose much.
And as you note about the circuits “beating” against one another, well, that is part of the anticipated result.
I’m still trying to decide how establish the series, parallel, stereo option potentials. I’ve only begun to populate the two PCBs so there is much adventuring yet to be done before I derive a final solution on how the two circuits will be conjoined.
As always, your viewpoints shed good light on things. Thanks again!
Thanks for that diode info. I’ll try that!
Sure Wilkie1. You’re welcome. If you don’t ind, I’ve another question regarding the Mini-Me mod switch setup. I could simply use a 1P4T rotary for that. could I not? Or is the 2P4T rotary required. I want use a dead-bug approach to the switch instead eating a bunch of internal real estate with the 2P4T rotary switch PCB (Roto-Tone).
I am very happy to share that a single LFO on the Mini-Me has sufficient voltage\current to drive the clock chips on two separate Mini-Me builds. I just finished testing a dual Mini-Me jig (“jig” as in wonky-wired with no stompswitches) and each has Wilkie1’s “depth mod” (wired dead -bug-style), with a 4P3T toggle switch to select individual LFOs or run both Mini-Mes off of one LFO. And it works precisely as I had envisioned and hoped. I also wired in a separate LFO speed indicator LED for each Mini-Me and they also work.
I played with all the controls in various settings and all the features work as I’d hoped.
Here’s the modified schematic with the LFO tap-point, added LFO speed indicator LED and a 1n5817 protection diode . . . .
Here are some of the build process photos . . . . .
And a close-up of the LFO sync switch . . . .
And finally, the intended candy wrapper for the 1590XX enclosure in which it will all go . . . .
I just need to finish the wiring properly to include the stompswitches and the sort out how to mount the LFO speed indicator LEDs. I’m thinking (hoping) they can fit in just above the “Left” and “Right” labels on the enclosure – mounting them so they are subterranean (just beneath the decal).
It will be wired in such a way that allows for stereo, mono series, or two separate choruses. Once I have all the wiring done, I will draw up a block diagram of the wiring, including the details of the LFO sync switch, and post to the forum and the FB pedal building group communities. This is an exciting build for me.
Wonderful work, Mark! Happy to know the single LFO worked for both!
You are also correct about the switch. The 2P4T Roto-tone switch can be used with one pole static.
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