i’ve made a Layout stripboard for the Active circuit part
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And TIL that there’s a new TL08xH series too. Unlike the non H ones, which have different supply and input voltage ranges and some different characteristics compared to the TL07xx versions, the TL08xH and TL07xH appear to have identical specs.
Here’s my build
I add avactrol CV IN with Attenuator on the Unbalance pot, and during the process of calibrate, i made some change :
replace the *33K by a 47K trimpot
and change the volume pot OUT by an Attenuator
I found i have better result like this.
A verified stripboard here
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As I embark on this build - how critical are the matched germanium/shottky diodes?
Would 4148s do the trick? I have enough of them that I could likely match 4.
Also it seems to me that diodes in general are often “just use whatever you have handy”. Is this a gross generalization?
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Stone himself:
Traditionally these diodes should be germanium, though Schottky diodes such as the BAT48 can be used. Even 1N4148 silicon diodes will work, though with greater distortion due to the larger voltage drop.
So feel free to use them, but something with a lower forward voltage will work better. I’m planning a build and I bought some germaniums, because I felt like sticking with the classic design. Otherwise I would have gone with Schottkys.
As for matching, Matthew Skala says:
I bought eight, and used the diode test feature on a DMM to pick out four with low and well-matched forward voltages for one of the ring mods. The remaining four went into the other. So I have a choice between a tightly matched and loosely-matched modulator. To be honest, I can’t really hear a difference between the two anyway.
Yeah. Diodes of various kinds vary greatly in their forward voltage, current capacity, etc. And of course Zeners are a thing of their own.
There are some situations where you can swap around fairly freely and others where you really should stick to something close.
But you can always swap 1N4148 for 1N914, because in reality they’re the same thing, and you can swap any of the 1N400x for each other, because they’re pretty nearly the same in all but maximum voltage (and even the lowest maximum is well above 12 V).
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For my build i used some BAT48
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So are all germanium and shottky diodes the same value?
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@Dud Would you be able to sketch out your cv vactrol control? I would be greatful!
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I must have done something like this
But since i think that a CV on the Unbalance pot is not very usefull on this module 
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If you do add a vactrol it’s best to use an op amp or transistor driver for the LED rather than trying to power it directly with the control voltage.
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Why is this? I’ve done direct LED driving without any problems before.
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Fair enough. I’m designing the panel right now and trying to decide if its worth including. I’ll probably just skip this one and reduce the parts count slightly.
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It’ll work a lot of the time, but it’s not best practice. Control voltage outputs are usually not designed with the intention of supplying milliamps of current. They’re meant to produce a reference voltage, not power. So you’re loading down the output stage on the upstream module in a way it wasn’t meant for. Besides, the LED won’t even light up until the CV is above the LED forward voltage, whereas with an op amp driver you can make the LED current (hence brightness, at least approximately) proportional to the CV, it’ll light up a little as soon as the CV is nonzero.
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Are both of these caps required? I imagine there was just extra smoothing required and two 100’s are easier to find than a 200
One’s a bypass for the TL071 and one’s a bypass for the NE5532. They’re about as “required” as bypass caps usually are, which is to say not very, but it’s good to have them, and it’d be even better if they were located closer to their respective power pins, e.g.:
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Yes 
! I don’t think I would make that “mistake” again today. I have learned a few things since 
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On the Mic in jack what other terminal is grounded? Ring, ring normal, or tip normal?
Ring and ring normal have to do with stereo signals so aren’t relevant here or in most synth circuits.
The schematic shows sleeve and tip normal grounded.
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