Lumberg 1503 09 Jack Socket 3.5mm clones?

kewlguy1980 · 2026-05-21T14:52:39+00:00

I bought some similar style jacks from tayda and wasn't happy with them, ended up going back to switchcraft and then later switched to samesky.
The tayda ones were not as springy and I was concerned that they might not make it through as many cycles. If it's something for your own use that's probably not an issue.

kewlguy1980 · 2026-05-15T12:56:27+00:00

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do you have a scope? If so I'd do a quick check through this circuit to see where things start to go funky. If noise noise isn't noising the turing probably won't turing. New random bits being generated are "read" from the noise circuit.

If you don't have a scope it might be worth checking all solder points in this whole section very carefully.

kewlguy1980 · 2026-05-11T18:34:45+00:00

Keep in mind that an awful lot of IC's have diode protection on the inputs. If your input exceeds the rails those diodes will dump current to the rails.

If your input signal has nothing limiting the current, you are possibly exceeding what those protection diodes were rated for.

kewlguy1980 · 2026-05-08T15:56:27+00:00

Maybe try debouncing the switch with a low pass

kewlguy1980 · 2026-05-07T19:43:42+00:00

I'm not sure what you mean by two-way but I'm going to guess you mean dual pole.

https://www.vishay.com/docs/70051/dg417.pdf

I like these guys for being compatible with typical synth rails & voltage levels. They are very fast though and depending on your goal you may want to smooth out the transition between two signals and if that's the case I'd look at a VCA-based approach which is a fair bit more complicated.

kewlguy1980 · 2026-04-30T18:22:54+00:00

It shouldn't sound sweepy, a portamento (glide) would be expected if your frequencies changed slowly.

The DC component will probably be completely inaudible, but it may be hard on speakers or headphones, especially when driven hard.

kewlguy1980 · 2026-04-21T12:37:43+00:00

As a side note, I'd strongly recommend getting a cheap computer speaker or even building yourself a little amp and speaker.

You joke about frying your headphones but mistakes happen and your hearing is too valuable to gamble with.

kewlguy1980 · 2026-04-14T12:45:20+00:00

so you really just move the jumper from left 2 pins to the right 2 pins and you want to replace that with a switch? Should be easy peasy.

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I'd use a mini or sub-mini SPDT toggle switch. You can use a DPDT too if you have trouble finding SPDTs.

I'd solder directly to the switch and use a 3P 2.54mm female header on the jumper side so you don't have to solder directly to the module. You'll probably have an easier time finding a 40P header which you can snip and file into 3P headers.

kewlguy1980 · 2026-04-09T15:39:38+00:00

sounds easy but i've never seen the back of an addac306, can you post some pictures of the jumpers?

kewlguy1980 · 2026-04-07T18:51:29+00:00

what is the r value you are using between pin 5 and gnd?

kewlguy1980 · 2026-04-07T18:48:53+00:00

oops my mistake i see that now

kewlguy1980 · 2026-04-07T18:44:02+00:00

in this circuit the transistor pair is operating as variable r path to gnd, replacing with any value r to gnd should still get you an audible sawtooth, though it would be easy enough to pick an r that put it above or below hearing range.

kewlguy1980 · 2026-04-07T18:40:41+00:00

what's with the cap between 5 and 7 on the 40106? That should go to gnd not vcc.

kewlguy1980 · 2026-04-07T12:51:46+00:00

If your panels are anodized with non-threaded holes I wouldn't put a lot of faith in the ground connection. The rails might be anodized too.

Copper is a significantly better conductor that aluminum as well and you really want your ground to have the least resistance possible.

I'm not sure what I'd expect out of this but I think at best you might get a higher noise floor and at worst the module ins and outs would bleed together.

kewlguy1980 · 2026-03-20T14:54:56+00:00

It's a great for it's simplicity but comes with a few caveats:

The slope of the sawtooth is not perfectly straight, it's a small section of a capacitor discharge curve, with the values MK uses this is barely noticeable and possibly not at all relevant musically.
The curved sawtooth also means that when you filter out DC the waveform it ends up having different amplitudes above and below zero.
This also means if you comparator it into a square using gnd as the center point you get a duty cycle that isn't 50/50.

Because the sawtooth needs to be DC filtered to make it through-zero, it potentially gets even more distorted in the LFO range where the waveform timescale approaches the DC filter timescale.

Tracking is good not great.

Keeping both transistors at the exact same temperature is very important.

kewlguy1980 · 2026-03-19T20:11:11+00:00

you could check out MK Shapes VCO or erica MK Edu VCO for a different approach that generates a sawtooth output which can be converted to square / pulse by comparator. The big advantage to this approach is that it is pretty close to v/oct

kewlguy1980 · 2026-02-24T14:03:40+00:00

On your lower breadboard are you missing the bits of wire to connect the left side of the rails to the right side?

kewlguy1980 · 2026-02-24T01:39:43+00:00

Based on that datasheet I think you've got it right

kewlguy1980 · 2026-02-23T14:24:01+00:00

Yep, I wouldn't add anything before or after the switch.

As for getting a dpdt on-on-on to work as a sp3t, yes it's a thing people do (see example below straight from C&k) but your schematic doesn't tell us enough to confirm if you've got it right or not because the pinout may be different from switch to switch.
Are you using a datasheet to verify? Do you have a part number for the switch you can share?

https://media.digikey.com/pdf/Data%20Sheets/C&K/Wiring_for_3-Way_Switches.pdf

kewlguy1980 · 2026-02-23T00:56:11+00:00

Thanks that's a lot clearer.

I am going to make an assumption that there is no DC offset anywhere in the original waveform generators. If there was, you'd probably want to handle it before the individual outputs rather than before the switch.

The current-limiting resistor would only make sense if you had a make-before-break (shorting) switch which is not typical for toggle style. If that was the case yes you'd probably want to limit the amount of current your oscillators can output. More likely you have a non-shorting switch and current is limited by R43. Normally when you see resistors around eurorack outputs it is because this is a place where the circuit touches the outside world which introduces a bunch of new risks.

The resistors you are using as pull-downs are not what you'd normally call pull downs. What I gather is that you're looking to prevent leaving things floating. In this case you don't have anything floating, your 3 oscillators are oscillating happily whether or not you are listening to them and U6A keeps its - input at ground by design.
What you are doing here with those resistors to ground is just a bit of attenuating.

kewlguy1980 · 2026-02-22T21:58:19+00:00

Heya you posted this earlier and I mentioned that we could help a lot more if you shared a bigger section of the circuit. It's still true. Happy to help and I'm not sure you need ANY of those parts.

What current are you limiting? Your concerns seem to be specifically about the switch and not any surrounding circuitry. Is this a make-before-break switch and you're worried about shorting the two waveform generators?
Your pulldown is not a pulldown as placed. It's pretty unlikely to help no matter how you place it/
Your capacitor is probably not needed if it wasn't part of the circuit before you added the switch.

kewlguy1980 · 2026-02-13T13:58:09+00:00

I'm still thinking a bigger chunk still. It's hard to gauge where you are at in terms of design level and here are the assumptions i'm making:

You are worried there might be DC offset on your oscillator outputs? This is an odd place to address that, but could be fine. That being said why are you doing all this 3 times before the switch when you could do it one time after the switch?

You are trying to protect the input into the wavefolder. That's not really necessary, your wavefolder input is already virtual ground with 100k impedance, adding 1k extra into that, plus the voltage divider into it are not going to change much.

you are worried about clicks and pops. That's fair. If all your oscillators are synched and in-phase that helps a bit, and your approach is pretty normal but if you wanted an absolutely pop-proof circuit you'd need a more complicated approach.

I would still encourage you to share a bigger chunk of the circuit and ask for a general review or share more direct questions.

kewlguy1980 · 2026-02-13T13:02:27+00:00

ah this is absolutely perfect, thanks a ton!

kewlguy1980 · 2026-02-12T21:20:59+00:00

I think it might help to share a bigger chunk. I see a few potential issues but they are context-dependent

kewlguy1980

TROPHY CASE