Serge thread

If the new 73-75 are exact replicas of the old systems there could be another issue - lack of buffering of sequencer outputs, causing a voltage drop when patching one output to multiple inputs. What this means is, you tune a sequencer row when patched to one oscillator (by ear or with a tuner), but then you decide to add a second oscillator, filter and so on, the first oscillator will no longer be in tune.

The CV Processor (1/2 of dual processor) can act as a buffer but this ties up a significant resource.
Alternately, a buffer can be patch-programmed using one section of the triple comparator, patching the comparator output to the “-” input and the signal to be buffered to the “+”, and with the offset knob at 0V. Instead of the comparator outputting a binary (0/5V) signal , it will act as a unity gain, with a buffered output at all voltages between 0 and 5V, which is generally the range of the sequencer output.

The reason this works is, the comparator without feedback is essentially an infinite gain applied to the difference of its two inputs, that clips between 0/5V. If you have negative feedback with a gain K, the overall gain is K/(1+K). Take K->infinity and result is a gain of 1 as long as the 0-5V limitation is obeyed. The comparator output is buffered and can be patched to many inputs without voltage drops.

In practice the gain is not really 1, or even linear, so you will have to tune the first oscillator directly from the comparator output instead of the sequencer row.

Again, I hope in the reissue they buffered the output (like modern Serge), but you can get around the problem with the comparator patch if this is not the case. There’s always this delicate choice, to offer more convenience, or to stick to the original circuits exactly – people complain in either case!

I think one can go far with this approach. A limitation is that one can’t transpose reliably by adding voltages. However there is more freedom in a sense. Anything now can be used as an oscillator with the same tuning procedure, for instance negative/positive slew, or filter patched in feedback, or some more complex feedback system. You don’t have to be constrained to the oscillators that track identically 1V/Oct.


Tuning a VCO with a Scalable VC Input - Patch of The Week - YouTube not perfect but I have been able achieve melodic results using the scaleable inputs on my 73-75 using this technique. Not usually my go to synth for pretty melodic stuff, very much excels at noise making and experimental/vintage patches.

I think if you want to explore serge, probably a more modern variant would suit your desire for melody and reliable tracking. I really love my build, but it came from a desire to explore period synthesizers as an act of historical recreation. I feel it’s important to warn people, it doesn’t compare easily to modern designs.


After struggling to decide what to get, I’ve just ordered an R*S La Bestia II and SQP4+ to jump headfirst into the world of Serge.

FS : 10 year + giant collection of Eurorack.


congrats! I’ve had a La Bestia II for a few years now and really love it.

did you order from R*S? I’ve been curious about their boats… do they include power distribution or not? because they have a separate power distribution item available on their site, which makes me assume it’s not included. and the power distro seems to be DIY only, which is weird. they also don’t look to have power cables on their site any more…

I’m hoping to do a 4x4 boat soon and I’m not sure exactly what to order from them. so maybe you or someone else could advise. Patch Point used to have these items but that doesn’t look to be the case any longer.

Low Gain has everything you’d need for power except for the boats themselves, fwiw. If you are handy you can get a boat from Hammond or Bud and get some nippers to cut out the areas that you don’t need to mount onto. I’m considering doing this, if you look at the prices for diy boats vs finished ones from people like R*S it’s a huge difference.


thanks for the suggestions! I actually have a power supply from Low Gain that I’d likely be using for this. so I could grab a cable from there too. I think three of the boats I’ve got are Bud or Hammond. I know full panels will work with those, but I’m not sure 4x4 modules will.


I think you’d have to nibble out sections and then drill holes each panel. Or, you can just nibble out the whole thing and use euro rails.

Aren’t the panel holes on these 4x4’s drilled too far in for Euro rails?

Nope, Ive got a handful of RS 4x4’s mounted to euro right now. They are just offset from the LW sizes. So I have a box with one row of all RS and another with LW sizes. You can peep it here:

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R*S connection options;

  1. Connection from the bottom
    mounting under a module a PSU board with connectors to which all cables are connected. From the PSU board an MTA -XLR -cable goes from the bottom of the boat to your PSU.

  2. Connection from the side of boat
    mounting a XLR connector with MTA connectors to the side of the boat (PSD KIT A), then you can connect all cables to it.
    With the superslim boat not all modules fit over the PSD.

I used #1. They mounted the PSU board on the VCFQ, and from there MTA-XLR cable goes through bottom. It cost additional fee as “Ready to Connect”

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For some reason I thought they were off by 2mm or so. I built my cases to LW specs, but have also had my eye on some 4x4s, so this is good to know!

So just to be clear… They are definitely off from LW. However, RS do fit on euro rails but you have to move the rails to align with holes. So if you have one boat or one row in a case with RS and one with LW it’s good, if that makes sense. It’s really annoying that the standards are different, R*S panels not only have different holes but are like 1/8" taller and 1/4" wider, for every 4" panel.

I have owned a handful of RS and LW panels, and I know both can vary depending on the builder, but I’ve found that the stock RS stuff sounds better to my ears than the LW stuff I’ve had. For example, the ResEq and the Wave Mult sound a bit more pleasant, a little rounder, and there seems to be way more sweet spots. Same thing with the filters. Just my take though.

I don’t see many conversations about the differences between Serge implementations and have been wondering about this. RS are the only ones sprinkling THAT VCAs and Burr Brown op amps on every design, right? I love the sound of my RS Euro Serge and had considered going R*S 4U, however since they moved away from DIY I simply cannot afford it any more. It’s unfortunate, I feel even though they never fully embraced DIY (i.e. no schematics) at least they enabled people to assemble modules themselves. But now the “people’s synth” aspect is completely removed from their business model.

EDIT: @moderators, how can I make this post a reply to the previous post after the fact? Thanks!


Could Elby PCB’s plus your own part selection be a potential road around this?

It would at least get the circuits behaving as you desire…

The circuits have to be adapted so I don’t think that’s a viable route. I remember dabbling with this in my Manhattan VCA and I didn’t have great results, even with chips that should have been drop-in replacements.

EDIT: I keep clicking the wrong reply button, sorry about that.

Fwiw, I only buy the 4u stuff used… It just takes a while to find it. If you keep looking on Modwiggler there will be some good deals that come up on Random Source, LW etc. The used prices for a R*S 4x4 Panel hover between $500 and $600 and if you think about the fact that you are always getting two modules in one the prices start getting pretty competitive to euro. I also just euro a euro power supply and made adaptor cables from euro to Molex. Keeps prices down too. I plan on starting to build some stuff soon, just for the experience and to really learn about it.

Thanks, I used to build two RS Euro modules, sell one, keep one. I also got into Euro when 300€+ was at the higher end of used prices, I mean I even got my Res-4 for 600€. So from this perspective, used RS 4U is a substantial investment that doesn’t really fit my budget.

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I haven’t checked in for a couple of days, and I see others have started steering you in the right direction to get melodic stuff out of the 7375 system. It’s doable. It’s not super easy, but I find it to be rewarding.

Also, there’s ways of trying to coax some semblance of v/o out of vco’s that aren’t set up to do that using scaling etc. I managed to do this on the Plumbutter and the Double Knot using offsets and scaling by passing sequencer cv through the Zoia and you can get usually get like 2-3 octaves happening.
Also if you have an Ornament and Crime laying around you can pass it through the O_C and calibrate a channel to be roughly ‘in-tune’ as well with an oscillator.

I’m still trying to find my workflow with Serge. Sometimes I make some simple feedback patches by using 2-3 modules and layer them with Octatrack, record it. It is a fun and fast workflow. Or I like trying to build a more complex patch which won’t be easy to figure out what is happening at some point. In this case my main focus is creating some kind of a conversation between different modules and record the result.

The last patch:

The problem with this workflow is the lack of control. Something like TKB would be great to use it to store some presets or a matrix mixer could help me as well.

For example, there is this new matrix mixer/sequencer which seems to be ideal to use it with a Serge system: Reliq Instruments

I even asked Reliq instruments if it would be possible to make a small batch of a version with banana jacks and they’ll check at a later stage and keep me posted on that. Maybe you can also contact them, so they can see that there is a demand for it :slight_smile: