Cadet BOM - Substitutions

Starting to build some cadet modules and running into some issues with Mouser being sold out. Wanted to get a sanity check on these before making orders across multiple vendors (or buying a wrong sub)

Various SPDT On-On switches (Cadet VII Processor, IX VCO):


Substitution with:

Cadet IX VCO:

TDK Multilayer Ceramic Capacitors MLCC - Leaded 0.047uF 50volts C0G +/-5%:

Available from Digikey:

Cadet IV Dual Ramp:

TDK Multilayer Ceramic Capacitors MLCC - Leaded 15uF 16volts X5R +/-20%

Available from Digikey:

For the switch I’d just use a normal panel mount ON-ON mini (not sub-mini) toggle and use some old clipped resistor leads to connect it to the pcb. I’m pretty sure I used the substitution you mentioned for my first one or two Cadets, but it’s not a perfect fit… The legs are a tiny bit too short, so you have to put the switch in at a not exactly perpendicular angle to the front panel. It’s not a huge deal, and I’m not going to change mine, but on all the other Cadets and Castles I’ve built so far, I’ve just been using panel mount switches and I feel much better about it.

Example I saved from someone’s facebook post a while ago of how to do it with a panel mount switch (sorry forgot whose post!):

The capacitor substitutions sound fine to me. The things to match when it comes to capacitors is value (obviously), general type (electrolytic vs MLCC), voltage, tolerance, lead spacing, and you might as well match the dielectric too. Looks like you got that right in all those cases.

And if those restrictions are too tight to find a substitution, the voltage, tolerance, lead spacing, and dielectric don’t always have to exactly match the spec’d part, they just need to be good enough, but knowing when they are often requires a bit of understanding the circuit:

  • Most eurorack circuits will never deal with a voltage swing bigger than +12V to -12V (so 24V total) and often the way the capacitors are used in the circuits they’re not seeing that max swing, so often 25V or even 16V caps can be used, but not always.
  • Tolerance of caps is like tolerance of resistors… higher tolerance is nicer but not always necessary depending on what it’s purpose is (though in video accurate caps matter a bit more than audio).
  • Lead spacing won’t affect the way the circuit works at all (unless the spacing causes you to have really long leads), but it’s nice to not have to bend some 5mm-spaced leads to fit into 2.5mm-spaced holes and vice versa.
  • And the dielectric doesn’t always matter either, though sometimes you don’t have much choice for a desired capacitance and tolerance and voltage combo.

always try to buy as much as possible from the same supplier as possible - and from as few suppliers as possible - to reduce postage - so I’d either buy from mouser or digikey unless you can help it

substitutes for the capacitors at mouser - there seems to be an improved susbtitute finder at mouser - if you scroll down a bit you can tick what you need from the present spec and these just showed up first in the list and look ok to me

mouser switches are quite expensive - I got some from tayda, I’ve not used them yet, but had a bit of a play with them and they feel the same as the mouser ones - but about 1/5 the price or something

Good tips!

I buy some thing from Ebay. free shipping .
Things like switches, certain potmeters and jacks can be very cheap.

I always get my jack sockets from Thonk in batches of 50 - they’re nearly half the price - but Thonk shipping to NL is not cheap, so I always try to add a lot of things I can’t get elsewhere in too

thonk also have reasonably priced switches - well, cheaper than mouser at least!!

potentiometers are pretty pricey - must have a look at ebay - as I will need some (a lot) more soon

looking at tayda for some resistors - they have a page where you can pick and mix 1/4W metal film resistors for $0.012 each - pretty handy

shrouded headers are also cheap from tayda - $0.18 each both 16 and 14 pin

they also have a coupon code at the moment - search for the Tayda Days thread on Muffs - it’s updated as and when

pity they don’t do 0603 smd parts I need an extra 100nF capacitor

will check arrow they’ve been good for single parts with free shipping in the past!!! and they also have a sale at the moment!!

This feels like a silly question but can I use 3.9K resistors in place of the 3.92Ks in the sync gen? Also, for the 0r resistor - cool to just place a lowly old link in there? Thanks!

yes you can use 3.9k (I think I did this too) btw: you can also measure the 1% resistors and see if there are some that are 3.92k

0r link is also a good option.

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Great, thanks. That’s what I was thinking. I’m more likely to find some that are maybe a little on the higher end of the spec than I am finding any 20r resistors to bridge them in my stash :+1: