DIY Project Recommendations

Rodrigo · 2021-02-21T14:39:32.391Z

That’s a good point.

I’ve used headphones in a similar way before, though it’s a definitely a specific kind of sound. I’m hoping for that overblown/distorted input (ala that vid above) so would be good to figure out how to tap into the mic audio.

cwpotter · 2021-02-21T15:19:43.793Z

Rodrigo:

I always presumed that these mics were “powered”, but in looking at the wiring I’m not sure how that could be happening with only 4 pins.

Yes, they are powered by the unit they are plugged into, I think that most apple stuff supplies around 2-3v via the mic pin. There’s usually a DC blocking cap as part of the power circuitry and the audio is taken off of that. If you do a search on electret mic power you’ll see what I mean.

Rodrigo · 2021-02-21T19:42:38.254Z

Gotcha, that makes sense.

Yeah, loads of shit comes up for searching that. I was searching for “headphone mic wiring”-type stuff and that led nowhere.

Will also order a bunch of tiny elecrets to do some testing with too.

rycolos · 2021-03-06T12:17:45.148Z

I could use some help DIYing a passive modular-to-line level box. Basically, this: Ladik P-520 4ch(out) line - Eurorack Module on ModularGrid

Despite building stuff for many years now, my theory knowledge is garbage. Playing around with a t-pad calculator (recommended by someone on the MW forum), I’m inputing an input impedance target of 1k (from modular) and an output impedance target of 10K (line level on my Soundcraft mixer).

Does that sound right? For a -20db pad, I’m getting roughly 400R for my input resistor, 1k for my output resistor and 700R for the bridge.

EDIT: Or can I make this simpler with just an L-pad and something like 10k on input and 1k on output? That doesn’t get me impedance matching though, right?

anon60283851 · 2021-03-06T13:54:28.055Z

Impedance matching is pretty much a thing of the past unless you want to connect vintage tubes and transformers type gear. To simplify (a lot), modern gear transfers voltage, which you’ll just want to attenuate, not power in which case impedance matching would be important.

So for attenuating modular signal levels when going in to a line level input, use a simple resistive divider, eg. Voltage divider - Wikipedia

Alternatively, a lot of prosumer and professional gear can take modular levels directly on line inputs without attenuation. I think my previous Soundcraft mixer did, so I could just keep the channel level down. So if you haven’t already, it’s worth checking whether the modular outputs actually do overdrive the mixer inputs at minimum input gain, if you haven’t already. (Of course if you prefer attenuating before mixer for some practical reason in any case, then that’s another matter, just a thought that might save some work.)

(To clarify: not saying impedances wouldn’t still matter - just that in practise with standard line / modular devices you have low enough output impedance and high enough input impedance that you don’t really have to worry about it in the first place…)

bmoren · 2021-03-06T14:19:52.236Z

Following up on @anon60283851 's excellent answer, here’s that idea in action

In a simple way (also the post above this):
Norns - Audio In/Out Specs? - #39 by bmoren

and in a more complex way:

github.com

bmoren/saturn-return

Modular level > stereo line out & stereo aux send mixer (a friend of norns)

rycolos · 2021-03-06T18:38:03.850Z

Thanks for the helpful info. I did try into my mixer and unfortunately got distortion even with the channel gain all the way down.

anon60283851 · 2021-03-06T19:27:52.646Z

In that case, attenuator it shall be

(And do remember, you can always use a normal potentiometer as a voltage divider as well, if you want a controllable one or aren’t sure yet what the best level of fixed attenuation is and want to try it out quickly…)

rycolos · 2021-03-06T20:57:57.133Z

Thanks! Isn’t the voltage divider you have there still a bit hot? Assuming 10v p-p on the modular side, that’s still 3v at Norns.

ETA: Duh. 10v p-p is 5v. So, that’s 1.5v at Norns.

infovore · 2021-03-08T08:21:53.374Z

3v p-p is still very hot for a line system powered at 3.3v, in my relatively inexpert opinion. When attenuating for, say, a guitar pedal, around 1v p-p reflects a guitar, for instance.

In general, might be worth making it easy to adjust any attenuation whilst you are fettling the levels.

rycolos · 2021-03-08T12:53:02.857Z

Fair point about adjustability. I was planning to just make some really simple modular to line level cables with fixed resistors (and thus avoid having another box on my desk) but maybe the box is the right move.

infovore · 2021-03-08T13:04:10.365Z

well - by ‘adjustability’ - all I mean is “resistors you could swap out if necessary”. Doesn’t need pots in the end. But for designing and fettling it, it’s useful to be able to get the values right before you “bake” them.

Zedkah · 2021-03-20T15:09:58.799Z

Any one have thoughts on these pre made synthesis circuit bulding blocks and how they might be used to make something interesting.
http://micromodular.pl/products
there are some guides on how to combine them to make a subtractive mono synth or a FM synth. I was thinking some kind of filter bank or more experimental thing , they only have 2 filters both lowpass.
Prices are very reasonable, thonk has them in uk and may be a way to add on some extra function to a diy build somehow.

thonk.co.uk

Syntaxis – Micro Modules – Thonk – DIY Synthesizer Kits & Components

dianus · 2021-03-26T00:32:20.612Z

This is really cool!! the price is quite good too. I probably already own like 10 devices that can do pretty much all of this but I’m curious anyway. Quite attracted to how delicate the little modules look

Zedkah · 2021-03-26T09:23:26.973Z

Yes its a shame it stops at the basics- a few more micromodules like a bandpass filter, delay,wave folder,and a bit of sequencing and logic stuff would really make this a great platform for people like me stuck at an intermediate/beginner level electronic knowledge. The noise module looks interesting but thonk dont seem to stock this one. Keeping an eye on this though hoping it expands.

Thanks for the video @dianus - he is getting good sound out of it- doesnt sound at all cheap or tinny.

infovore · 2021-03-26T11:00:45.033Z

So what these modules really are is just breakouts of a bunch of CEM and SSM chips (or their clones), which makes for easier prototyping or design. Hence: the 3340 VCO (as found in the SH101, etc) which I’m fond of; the 3320 VCF, as well as the SSM2040 VCF, the 3360 VCA and the 3310 ADSR.

They’re the building blocks of a subractive synth because… that’s exactly what the ICs they’re based on are - the building blocks of classic 80s subractive synths. The Syntaxis modules close to the datasheet circuits, leaving you to just add IO, controls. Although I’ll note that certainly in the case of the 3340, some decisions appear to have been ‘made for you’ at the module level - eg the way that chip likes to do sync or PWM have already had some decisions made on the module, from what I can see.

The datasheets for the ICs themselves have straightforward examples of how to build them up, and you can compare them to the Syntaxis products to see which parts have already been ‘done’ and which are left as options.

The filters in particular are a little disappointing - in that they’re set into one filter topology/configuration (eg: the 3320 is just set up as 24db lowpass) when, in fact, the point of that chip is that it’s easily configured into any combination of four poles, as Electric Druid has pointed out in their excellent blogpost on 3320 filter designs. The Synthex LPF/BPF/HPF, or 2 pole LPF, or any HPF design, just aren’t possible; it’s already been set up as a 24db LPF and that’s it.

So: the bandpass filter is an option that’s denied to you. A lot of the other circuits you describe are more discrete in nature (like their µnoise board, which is a neat selection of functionality), rather than just being ICs broken out as per the datasheet.

I like them because they’re nice ways to explore these building blocks on a breadboard… and at the same time, if you can wire together the Syntaxis modules on a breadboard, wiring up the CEM 3340 datasheet circuit - or any other of the VCO designs Tom describes on that page - is also within your grasp. The great thing about the Curtis chips was how much they did on board, and how little extra componentry they need to bring them to life.

karst · 2021-04-05T20:30:44.132Z

has anyone built a Hyve? it looks like it’s all smd, but wanted to see if anyone had an opinion on whether it was a poor choice for a first smd-heavy project.

forrest · 2021-04-05T20:34:49.915Z

He sells the boards as a pair, I built two a while back, it’s a very easy build just a couple op amps, 0805 resistors and some transistors… Great first SMD project.

hermbot · 2021-04-06T15:59:17.656Z

I still have one of those two! Great little box.

ldezem · 2021-04-10T18:23:14.043Z

Thinking about building a Befaco i4 Instrument Interface to serve as a preamp for semi-pro voice-over recordings. Would it sound clean? I wonder. If the output would driven straight to a RIP would it sound lush? I wonder.