RCA Sync adapter

I made a layout for a simple 14pin sync to RCA sync adapter.
Same as on my sync busboard, but without the busboard.

To be able to connect modules that use the CSync RCA connector to your DIY setup.
small board style, with better RCA connectors


Great riff on your sync bus board!

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Couldn’t wait for the LZX Sync Distro, I take it? :slight_smile:

no, this is more a project that came out of need from myself.
I might even make it an adapter MOD board for the sync gen, tiny pcb
Sometimes I get requests for this type of thing
I figured some people might find it useful to add some LZX modules to their DIY setup, without the having to use the bigger sync busboard.
No idea what the LZX thing will look like. or when that comes out


Suggestion: add provision to feed sync to the pins on the euro power connector that the Castle VCO modules use. I’ll grab a couple if you do that :slight_smile:

I was also thinking that. I have the same issue with that method of the clock VCO
But I thought: what will happen if that signal is already present? (or any other signal, like CV+ gate from a doepfer system. )

Well, if there’s another signal on those lines then that’s what the Castle VCO will see as sync. So you should just not do that :slight_smile:

I think that’s probably why LZX is moving to the new sync system, to avoid the whole issue.

I guess the other option that would be useful is to have the RCA sync able to be the source, feeding into the old-style 14 pin sync connector, so you can use older Cadet modules (Ramp Gen, VCO, RGB Encoder) in newer systems.

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I think that is what LZX is going to do with their distro board, if I recall correctly.

I’d be interested to see a SMT version of this for Cadet I where it just plugs into the 14/16 pin connectors on one side and has a 14/16 pin pass through connector with an RCA sync out. Something like this idea:

Doesn’t it get too big like that, to fit next to other boards?
it might be doable if I put both connectors on the same side…

It is a good Idea.
The power header and the sync are pretty close together.
I will do some tests :slight_smile:

Yeah, it would likely need to be placed next to a skiff friendly module to be assured clearance but it kind of helps that Cadet I is already pretty deep.

I probably will keep on using your Sync Bus board for my setup (needed more 14 pin connectors and RCA out) but may solve sync issues in a compact way for a few Cadet I users.

In an effort to extend the life of my Cadet system, and allow me to add some of the upcoming gen3 modules (that need RCA sync), I’ve started working on something sort of like what you suggested. The scaling and buffering is straight from @reverselandfill’s schematic above, pretty much:

I want it to plug in to both the power and the sync, passing it through and tapping them for its own needs. I think I pretty much have everything fitting, if I use a SMD LM6172:

I’m not tied to this particular type of RCA jack, so if anyone has a suggestion I’ll consider it. Also, if anyone spots anything wrong or problematic with the schematic or layout, please let me know!


Oh and if anyone has some good measurements for for the spacing of the headers from one another and from the holes, that’d be really helpful. All I have right now is a ruler and it’s not exactly precise. The measurements I want (or want to be able to derive) are shown below:

Just to be clear about the measurements I’d ideally like:

  • A is from the middle of the lower mounting hole to the middle of the topmost pins of the power header.
  • B is from the middle of the lower mounting hole to the middle of the topmost pins of the sync header.
  • C is from the middle of the lower mounting hole to the middle of the top mounting hole.
  • And I just realized I could also use info about the horizontal alignment of the mounting holes with respect to the power/sync headers, too.

Thanks anyone who can help. (And extra thanks to @Z0NK0UT or anyone else at LZX who might be able to hook me up with the official measurements of those distances!)


@reverselandfill Did you ever build your original version of this? If so, did it work OK?

Also, are C2 and C3 oriented correctly in your schematic? It seems to me like maybe the + side should be facing the circuit, since that’s the side being driven and the other side just gets terminated to ground (in whatever module it’s connected to). Though I’m not sure if that’s the right way to think about it. Also I’m not sure if it even actually matters.

Ah shit, I’ve just seen your post now about the measurements, surely you’ve gotten them since you posted, right?

I actually haven’t, but I gave up on that kind of extension board since my Cadets were moved to a case that’s too shallow for Cadet 1 to be any deeper. But I started making a small board that does the same thing, but without plugging directly into Cadet 1. It’s just a 1-output version of reverselandfill’s board above, and since it only has 1 output and I rearranged things, it’s even smaller. I’m hoping it’s small enough that I won’t mind it dangling in my case (maybe once covered with a little cardboard for shoddy short circuit protection?). It does have mounting holes, but I don’t want to drill extra holes into my new case just yet.

Here’s another hacky approach to getting RCA sync to the inside of your case with a Cadet I–just wire up redundant RCA connectors in parallel!

I have both rear connectors routed to a rear panel I use to keep RCA cable clutter out of my usual patch cable spaghetti. Top goes to the genlock input and bottom is the buffered RCA out for loopthrough. They’re basically just redundant connectors for the front panel.

Of course, you do need to have something plugged into the genlock input for anything to come out of the bottom RCA out.

Ignore the circled part, that’s how I implemented the pull up/down resistors on the VCXO with a switch based on this discussion:


no, I didn’t
but another simular & expanded thing might be in the works .

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