8hp Ramps Adaptation

This is a continuation of a Facebook group post you can find here:

I’m working on a skiff-friendly 8hp version of the Cadet IV (ramps) module for myself, but as it seems like more people are interested in it, I’ll likely make it available for the community in one way or another – either a hybrid DIY thru-hole/SMT PCB/Panel set, or potentially a complete plug and play module. I’ve already planned and designed most of it, and it still is chiefly just a project for myself, so there’s not a ton of wiggle room that I’m willing to negotiate about, but I’m not so closed-minded that I won’t listen to ideas or requests.

As it is now, it’s an 8hp module with all the outputs of a Cadet IV and additional H & V triangle outputs hardwired through Cadet X (multipliers) in 4Q mode to provide adjustable fixed-frequency sines-(ish). The C-IV trimmers have been changed to 500k and moved to the front panel for convenient and wide-range control of the amplitude. The front panel has bias and attenuversion controls for the multipliers, which will be center-detent if I can get them dialed in the way I want. I’m gonna try to cram in CV inputs for the multipliers as well, but I’m not sure they’ll fit. If it comes down to available real-estate, I might sacrifice the sawtooth outputs for multiplier CV ins.

The things I’m not going to alter are:

  1. 8hp
  2. The front-panel as it’s described above

Two things I’m still considering:

  • How the module will receive sync

I prefer the “@pbalj method” of H & V distribution, (through the power header) and I’ve modded a few of my modules to receive sync through it. Left to my own devices, this is probably how I’d do it this time as well. I think the circuit would need to be altered, because the CIV design doesn’t seem to get triggered by the 1v pulses supplied by C1, and it appears to be designed around receiving 5vTTL from the 14 pin sync header. I personally dislike the 14-pin header, and it seems to be getting phased out (although I could be mistaken?). The other option would be a posterior RCA jack which would require more parts, more cost, more complication, and would also not be useful for me… I guess I’m asking if you can live with receiving H & V pulses via the power connector. It makes perfect sense to me, but people seemed confused by the Castle VCO.

  • Component footprint

I prefer SOIC chips to pdip, but I also like using through-hole passives. If this is going to be a DIY thing, are people terrified of SOIC? Personally, I find it easier, quicker, and it saves a massive amount of space. I still like through-hole passives though – just my preference FWIW.

Thoughts?

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I’m super in for this. Really want a low profile ramps module that does a bit more than the Cadet. Personally I don’t care if it’s larger than 8hp, this would be an incredibly useful thing to have. I’m not sure about the whole power bus sync thing. I haven’t tried to get it working on my system yet.

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Probably not a representative user, but not at all afraid of smd’s, especially not big ones like soic.

“Advanced ramps” is interesting to me, but if there is panel space i’d rather see the squaring function normalled rather than hardwired?

No opinions on sync, it all works.

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I am interested in this as a diy pcb, possibly (if at all possible) would be good with the smt parts pre assembled as I don’t own a toaster oven lol. for a front panel could just drill out a blank 8hp panel to fit. I think ‘posterior RCA jack’ sync is ok, but also ‘through the power header’ sync does work if it works why not

I currently use Cadet 1 as a sync gen/ input, but planning to use a tbc2 once I can get my hands on one. I am assuming that tcb2 can act as a master sync gen and distributes sync via cvgate bus. then I still have the problem of how to get sync from the rest of the system to the final output Cadet 2 RGB Encoder. I guess another useful module would be a skiff friendly Cadet 2 RGB Encoder with rca sync in/out. I have been thinking about trying diy on KiCAD to make some of this stuff myself. but I’m prob in way over my head there.

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Super interested in this one!
Also a 14pin to H&V should be fairly simply to produce.

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Hi Petro

the SOIC chips can be hand soldered quite easily - check out drag soldering on youtube

alternatively a hotplate can be used

I think you might need to keep the cadet1 as the master sync with the tbc2 - and the tbc2 will probably only have rca sync

as far as I can remember all eurorack lzx master sync modules output sync on the power bus (cortex, cadet1) as well as either the 14 pin header or the 14pin header and rca, so as long as the module needing power bus sync is on the same power bus as one of the sync generating modules then everything should be ok

check out reverselandfill’s video sync bus it can take either rca or 14pin in and has a lot of 14 pin headers and 1 rca header if you need to interface between rca and 14 pin systems in the same case easily

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for clarification: the sync busboard has rca out, not in.

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Yeah true , I kind of want/need something that does the opposite of your sync bus board , RCA to 14pin with RCA in / out (thru), probably not that complex of a circuit to try put together in KiCad for a first attempt at PCB design, considering that the schematic design for converting sync are posted in this forum , ( in your article about the sync bus) , sorry to sidetrack this thread :slight_smile:

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I’m really into this. I too like SOIC… plenty easy. SOIC + TH passives is what I’ve mostly settled on for my planned DIY modules. I also like the sync via power header method (since I only have Cadet and Castle video modules so far, so it works well for me).

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14-pin pros/cons.

Pros:
Simple to produce – no need to alter the circuit.
Nobody will be confused by it.

Cons:
Takes up a lot of PCB space on what will be a tight board already.
Potentially obsolete.
Will have to alter the circuit, which might end up taking up the same abount of space.

I drew up a schematic for that circuit (I think) in case I wanted to use it for my oscillator module, but decided to just use the power header instead. I haven’t tested it, but I can share it if you’re interested. It’s basically just lifted from the C1 schematic.

I can imagine some small pcbs, ala MI +5VSource (probably a bit bigger) and that gets connected directly to the power board and injects the H&V from either 14pin or RCA. Or two versions even, one legacy/cadet 14pin and one Expedition with RCA.

Well, so far it seems like people are on the same page as me, and we’re also going to end up teaching @petro how to hand solder SOIC, which is great (it’s easier that you think).

Development will take me a few months probably, but I’ll try to keep you all in the loop – posting updates as they happen.

Out of curiosity, how would people feel about sacrificing the sawtooth output (inverted ramp) for a multiplier CV input? I did a hardware layout on my bench and I don’t think it’s possible to fit 6 pots and 10 jacks on an 8hp panel, and even if I could, I’m not sure I’d want it to be that crammed in there. Thinking out loud here – the tentative front panel would be H amplitude pot, H multiplier bias pot, H multiply pot, H ramp jack out, H triangle jack out, H multiplier (quasi-sine) jack out, H multiplier CV in, and then the same for V.

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I’m not all that excited for offset/scaling of outputs, unless they’re inserted somewhere i couldn’t reach before. The cadet modules generally have knobs for most inputs, and since i usually want to duplicate a signal before i scale it, i’d rather have more features than output scaler knobs.
I would love to see a bias knob and perhaps an offset input placed before the saw->triangle folder so you can move the centrepoint.
In the same vein, since “everything” has attenuverters on the inputs, the reverse saw is less useful and possible to recreate with processors if needed.

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To expand: together with the squared outputs (i think we might also want to clip the negative before the square function) and a key, this will allow you to draw circles/ovals/diamonds and move them around the screen

re: saw, that’s exactly what I was thinking. to be clear, the outputs will not have offset/scale controls. the amplitude pot will move the center point, as you described, and that will definitely be in there – it’s something I already put into my current ramps module, and I use it all the time. The other controls that will likely be in there are CV bias for the multipliers, and multiply.

It make make more sense to explain that the impetus for this module wasn’t so much to create a shallow ramps module for the community, but to panelize one of my perma-patches. My ramps triangle outputs are always going out into multipliers, and it’s taking up more space and adding more complication than I’d like. My panel is already 8hp, and there’s more room for me to fit the extra things in there comfortably.

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You are describing the module that had already started to form in my head before you posted this thread, so i’m guessing what “the community” needs is pretty much what you’re making.

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or, i think i envisioned folding the “square sum” and the comparator into a single circle-drawing module, with normalled inputs to allow me to insert oscs in place of the ramps if needed

Cool, sounds good. Technically, I can fit all of it on a panel (including the saw), but it’s a pushing the ergonomics even by Eurorack standards. Losing the saw would open up the panel space a bit more and also probably save some space to make cleaner routing on the PCB. I’m leaning that way… The outputs might have one inverted and one not though, whichever arrangement natively makes a video raster is what I’m going to go with if i lose the extra outputs, and I vaguely remember that one of them needs to be inverted (could be wrong).

Re: normalled inputs: easy enough to implement that.