Jack socket size

Does anyone have experience changing a 6.35mm jack socket for a 3.5mm socket in diy modules? I want to try making my own module. Do you need to change any of the resistors in the circuit for a different size socket or is it fine to just wire in a 3.5 socket?


no reisitor change only smaller hole for 3.5mm socket , as you see 6.35mm socket is bigger … All is good , especially if you are drillling your own holes or have them drilled 3.5mm size. You can see if you try and put 3.5mm into a 6.35mm hole is gonna fall through. Welcome to the group much fun building, share again cheers


You can use 3.5 mm sockets in 1/4" holes if you use washers.


I’d say the only thing to watch out for/be aware of, is the use of the closed contact on the jack socket, and connecting up the legs the right way around. I’ve not compared a Thonikicon with a normal 6.35mm jack, so not sure if the contacts are on the same side/legs map the same way. You can test this with a multimeter and run continuity on the legs when a jack is inserted.

6.35mm jacks also have closed contacts on the sleeve, so check to the schematics to see if they’re being used or not, or just tied to the ground plane.

And same applies for use of stereo 6.35mm jacks, AFAIK won’t map to Thonkicon green stereo jacks. The green jacks don’t have closed contacts for both channels, as one leg is T and one is R. But if there’s a stereo output anywhere, you’d be better off breaking out into two mono Thonkicons.

Checking the schematics on Thonk:

  • mono 1 = sleeve, 2 = tip closed contact, 3 = tip
  • stereo 1 = sleeve, 2 = ring, 3 = tip

With a mono 6.35 jack, they’re 4 pin with both the sleeve and tip having closed contacts, and with stereo 6.35 jack they’re 6 pin, with the ring having a closed contact as well.


Thanks for the reply! That’s super helpful!


[Edit: A few things corrected]

The switched stereo 1/4" jacks most commonly used in Kosmo designs have five pins: Tip, tip switch, ring, ring switch, and sleeve. You can get unswitched stereo (tip, ring, sleeve) or switched mono (tip, tip switch, sleeve) or unswitched mono (tip, sleeve) as well. They can be panel mounted or board mounted in vertical orientation. Most of LMNC’s Kosmo module designs, and many other Kosmo designs, have footprints for board mounted, vertical 5-pin switched stereo jacks.

Ring and ring switch are not commonly used in synths, except for headphone jacks. But stereo jacks can be used as mono, with ring and ring switch left disconnected. Since these are cheaply available, e.g. from Tayda which does not carry similarly low cost 1/4" mono jacks, they are what get used often.

There are many 3.5 mm designs commonly used, including Thonkiconn jacks. Typically they are mono jacks with three pins: Tip, tip switch, and sleeve. These correspond exactly to the similarly named pins on 1/4" jacks (mono or stereo). Of course the footprints are different, and if you want to use 3.5 mm jacks with a PCB designed for board mounted 1/4" jacks you would have to use panel mounted jacks and run wires to the corresponding pads on the PCB.

Though many Kosmo designs have most of the parts on one board and the jacks on another, connected via pin headers, and then it’s simplest to just omit the second board and the pin header and wire the jacks directly to the pin header pads on the main board.

If you’re building stripboards or designing your own PCBs, you just have to wire the 3.5 mm jacks accordingly or provide suitable footprints for them; but they connect electrically in exactly the same way as 1/4" jacks.

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The most common 6.35mm jack sockets in Europe are either 4-pin mono or 6-pin mono.

RS, Farnell and Rapid do 3.5mm in a wide range, including 5-pin double switched, but not as panel mount. In the US, RS trades as Allied.

The Thonkicons are panel mount as well, so are a good option, just add fly leads back to the PCB.

But I would advise checking the schematic, as many modules like mults use the tip switches to bridge or isolate the signal across multiple outputs. Many designs also tie the tip switch to ground to reduce noise.


Apologies, thought we were talking about Kosmo designs. The 5 pin switched stereo 1/4" footprints are most common here. In fact it’s the only 1/4" I’ve seen used for Kosmo modules.

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In addition to the “Tayda” ones, I also use these cheapo jacks on prototype modules:
Screen Shot 2021-04-29 at 15.20.22

I have never used the ones posted by @bymccoy , but I think of cases I may (the PCB mounted one, not the one on @bymccoy 's picture)
I have to get a few to check the dimensions…