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Behringer Model D - DIY Mods
Old 19th March 2019
  #211
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Maffez's Avatar
ah, and another one, since you and andy mentioned groundig above. needed to ground a whole bunch of jacks and pots for a quadruple 3340 vco thing and just wired al ground lugs of pots and jacks in series and the last of them to a ground point (not the case) - so you have only one wire to attach. the boog has several gnd places, as andy mentioned, as well as a designated testpoint gnd - left side of back on pcb, close to the 1v/oct tp
Old 19th March 2019
  #212
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Makes sense. So just combine all neeeded mod grounds and lead em to the gnd point near voct should be fine?
Old 19th March 2019
  #213
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Maffez's Avatar
yup
Old 19th March 2019
  #214
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Uhm since i got your both attention maybe you can excuse one more drift off topic.

That DI i am modding has a 10:1 modern iron, so if i leave it there and do my ramp up/down with 2 vintage irons afterwards i will be save without a buffer (180k).
On the out it has 200ohm that i can work with with my other irons. My question woukd be when driving the old iron is aim, if the modern one in front would somehow due to physics hinder my aim and kind of tame things unwanted? Or doesnt it really matter?

My mixer expects 160-600 ohm and i can wire the old iron out for 200.
Old 19th March 2019
  #215
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no worries, drift is cool. unfortunately, i don't really know anything about iron, except we're talking textile-related
Old 19th March 2019
  #216
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Quote:
Originally Posted by Maffez View Post
about pwm mod point, see pic. i just used the pin of the rotary switch.
Could you point to it on the schematic that's shown on the page for PWM in your mods document? (attached).

I can see two points where a voltage (or resistors to ground / -10V) would alter it. I'm guessing the lower one (B), but I wasn't sure, from the description.

Probably just experimenting with values is best anyway, but it would be nice to understand it better too.
Attached Thumbnails
Behringer Model D - DIY Mods-pwm-mod-where.gif  
Old 19th March 2019
  #217
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Quote:
Originally Posted by ion-five View Post
That DI i am modding has a 10:1 modern iron, so if i leave it there and do my ramp up/down with 2 vintage irons afterwards i will be save without a buffer (180k).
I'm assuming by "iron", you mean transformer? Is 180k the input impedance?

A higher impedance coil is safer, because the back EMF can only deliver a smaller current. Whether it's safe enough, I don't know.

Have you considered using the headphones output, and a splitter to take one channel? That's okay driving 32 Ohm coils, so you're not likely to damage that.

Both left and right channels are actually the same signal but you'd need something like a 3.5mm stereo jack to RCA lead, then use one RCA plug on an RCA to 6.35mm (1/4") jack plug adapter to plug it into the DI box (a guitar jack plug with an RCA socket on the end). Those are common, and easy to buy.

Ideally, insulate the unused RCA plug with something so it can't short out on anything - even just a plastic bag and a rubber band.

Since you're modding anyway, you could even fit a new socket, wired to one channel of the headphones socket.
Old 19th March 2019
  #218
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Maffez's Avatar
Quote:
Originally Posted by AndyHornBlower View Post
Could you point to it on the schematic that's shown on the page for PWM in your mods document? (attached).

I can see two points where a voltage (or resistors to ground / -10V) would alter it. I'm guessing the lower one (B), but I wasn't sure, from the description.

Probably just experimenting with values is best anyway, but it would be nice to understand it better too.
Sure. Page 1, Section 7 A/B for VCO 1

Waveform switch (here 3 a and b) has two funtions: 3a selects waveforms, 3b selects voltages for regulating pulsewidth (see also R136, r153, r163)


Most proper variable PWM way would be to decouple those resistors and put a pot between -10v and ground and feed the outut of that to the pins of switch 3b, which I was reluctant to do so far. Would need some mapping/searching on the pcb though.
Old 21st March 2019
  #219
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Quote:
Originally Posted by Maffez View Post
Sure. Page 1, Section 7 A/B for VCO 1
Thanks. What I meant to ask was which specific junction point, on the schematic, relates to the solder joint you've marked as PWM IN.

I think I've figured it out though - the switch switches two points on opposite sides, to two other points, so it seems to be Pulse 2 - the shortest one, which I marked as B, on the bit of schematic in the picture above.

I thought it was probably that one, because it looks like it should give the biggest effect on the shortest pulse setting, some on the next one, and a little on the square. I wasn't sure that's what you meant though.
Old 21st March 2019
  #220
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Quote:
Originally Posted by AndyHornBlower View Post
Thanks. What I meant to ask was which specific junction point, on the schematic, relates to the solder joint you've marked as PWM IN.

I think I've figured it out though - the switch switches two points on opposite sides, to two other points, so it seems to be Pulse 2 - the shortest one, which I marked as B, on the bit of schematic in the picture above.

I thought it was probably that one, because it looks like it should give the biggest effect on the shortest pulse setting, some on the next one, and a little on the square. I wasn't sure that's what you meant though.
ah, now i get it

yes, exactly this - pulse 2 on account of cv in having the biggest effect
Old 21st March 2019
  #221
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Can you guys think of any mods that would take processing of external audio material on another level in terms of complexity? Or do we reach the limit of how a minimoog is designed? I think about envelopes mostly, arp like, grain synthesis like things.
Any ideas?
Old 21st March 2019
  #222
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Wouldnt a filter mod that exploits the HPF open up cool things like bandpass. So an extra physical input for the hpf and some pot control?

Or a few fixed frequency passive filters. Too bad notch and comb are most likely out of the question
Old 21st March 2019
  #223
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And a bit of a diy noob question if i add rotary pots to things like the pwm, how do i actually know wich pin is what as i think they arent labled and are mostly 3 while i just use one hot pin and ground right?
Old 21st March 2019
  #224
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Asking for advice please, scratched the topic earlier but i need to be sure.

Is it possible to use ADSR shaping for external audio at all or not?
Thats super important to me to shape sample instruments with an Envelope.
Old 21st March 2019
  #225
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Maffez's Avatar
for pots, google (which pin basically determines the direction of max/min, middle pin is "out")

as for adsr shaping, I assume, you want to control the level of a signal, and yes, that's possible. level adsr controls a vca, which you can feed with using ext in and filter open or use the "direct vca" in mod. adsrs never shape audfio directly but control vcfs vcas etc.

as for hpf & bandpass fun, as far as i know, the hpf implemented on the boog is based on an early mod/extension that deviates a little from other hpf designs; if i get it right, it basically inverts the lpf out, so parallel lpf/hpf use might not be a thing

as for external audio processing, without extra components you're basically stuck with the usual vcf/vca thing, i.e. elaborate waveshaping or delay effects are not in there per se; yet, audio rate modualtion of some parameters like cutoff might already give you a bit of extravaganza

cheers
Old 21st March 2019
  #226
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Was confused there from digitsl synths where shaping attack and release of any waveform, also audio is possible...
Old 21st March 2019
  #227
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Maffez's Avatar
Quote:
Originally Posted by ion-five View Post
Was confused there from digitsl synths where shaping attack and release of any waveform, also audio is possible...
ah, i see. nah, not as easy in the boog without greater effort (you'd need additional vcas for that)
Old 24th March 2019
  #228
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Maffez's Avatar
just saw this in the behringer eurorack modular thread

EURORACK 104 | Accessories | Keyboards | Behringer | Categories | MUSIC Tribe

plenty of space for the boog, a power connection panel and extension panels
Old 27th March 2019
  #229
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This is sort of off the current topic, but would it be possible to convert the factory Boog to use better components, larger knobs, switches and 1/4” inputs/outputs? I’ve never been a fan of the mini synth craze started by Roland with the Boutique series. I understand this would require a different chassis....

PS- Ultimately I would love to one day have 8-16 Boogs under 1 giant hood poly chained as one big poly synth.
Old 27th March 2019
  #230
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Quote:
Originally Posted by Moogerfoogers View Post
mini synth craze started by Roland with the Boutique series.
It was started by korg with the monotron series
Old 27th March 2019
  #231
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Maffez's Avatar
Quote:
Originally Posted by Moogerfoogers View Post
This is sort of off the current topic, but would it be possible to convert the factory Boog to use better components, larger knobs, switches and 1/4” inputs/outputs? I’ve never been a fan of the mini synth craze started by Roland with the Boutique series. I understand this would require a different chassis....

PS- Ultimately I would love to one day have 8-16 Boogs under 1 giant hood poly chained as one big poly synth.
with enough effort, certainly. components as such are not actually bad quality at all. as for size, yeah, you could desolder all pots, switches, jacks, and rewire them into a bigger case, yet that'd be quite some work. the normal pots and jacks are halfway doiable (tried), but the siwtched pots and switches, phew... although they might seem flimsy on the top (like the caps on the switches), they're soldered very solidly onto the pcb (all mechanica components on the boog are through hole)

as for poly chaining, you'd need to consider that changing a parameter in such a poly, say attack time, would require you to either go for more complex ic-based design or turn 8-16 attack time pots - which i why i personally find paraphonic use more sensible for my needs (used to have a vermona perfourmer and go tired of dialling in poly patches in such a way)
Old 28th March 2019
  #232
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Quote:
Originally Posted by Maffez View Post
as for poly chaining, you'd need to consider that changing a parameter in such a poly, say attack time, would require you to either go for more complex ic-based design or turn 8-16 attack time pots
Yep. It's doable for things with only simple controls, like the Monotron, but even for a basic mono synth with an envelope or two, it gets unwieldy.

If I had to do it, I'd replace all the pots with digipots (IC based). Those normally only give you 8 bits of resolution, so you'd probably want pairs of them for some controls - e.g. the filter cut off, to stop it sounding steppy (i.e. a course and a fine control).

You'd then need a microcontroller to read physical controls and send values to the digipots - so it could control them on all voices at once, and recall patches.

At that point, what you'd essentially have is a Roland SE-02 for each voice - except those only have one digipot for the cut off, which is a bit of an issue.
Old 30th March 2019
  #233
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Guys can i ask you one more not model d related thing?

For my DI i got a wire wound 500ohm Potentiometer. Good old stuff t be used as attenuator.

Now it came in a pait of 2 and i was thinking putting a simple audio attenuator in my eurorack with the 2nd one.

Can i do this wih a wire wound 500ohm 1-2 watts pot? Or will i damage sth or get ugly results?
Old 30th March 2019
  #234
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Maffez's Avatar
Quote:
Originally Posted by ion-five View Post
Guys can i ask you one more not model d related thing?

For my DI i got a wire wound 500ohm Potentiometer. Good old stuff t be used as attenuator.

Now it came in a pait of 2 and i was thinking putting a simple audio attenuator in my eurorack with the 2nd one.

Can i do this wih a wire wound 500ohm 1-2 watts pot? Or will i damage sth or get ugly results?
500ohm is not really much for audio attenuation; typical values for mixing purposes you'd fine online are 10k, 47k, 100k


that value is more along the lines of fine-tuning after a pot with higher values, so that might be a purpose?
Old 30th March 2019
  #235
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The main purpuse is to tame the output after the transformers a bit down yes. So 100% silent is not needed. I was thinking 500 ohm would be fine with a transformer that has max of 500 ohm.

Any idea how much db i could attenuate that way?

And i have no cloue how a 500ohm pot would behave within the modular. And how much attenuation i would get. Around 50% would be fine i guess in both cases. Is that realistic?
No idea if it would work for cv too?


Or should i add a resistor in parallel in both cases? If so what value? I still have 2 dale cmf55 1k 1& ones.
And how to add it actually, just soldering wit the wires to the pot pins?
Old 30th March 2019
  #236
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Maffez's Avatar
Quote:
Originally Posted by ion-five View Post
The main purpuse is to tame the output after the transformers a bit down yes. So 100% silent is not needed. I was thinking 500 ohm would be fine with a transformer that has max of 500 ohm.

Any idea how much db i could attenuate that way?

And i have no cloue how a 500ohm pot would behave within the modular. And how much attenuation i would get. Around 50% would be fine i guess in both cases. Is that realistic?
No idea if it would work for cv too?


Or should i add a resistor in parallel in both cases? If so what value? I still have 2 dale cmf55 1k 1& ones.
And how to add it actually, just soldering wit the wires to the pot pins?
not a bad place to start here: Potentiometers (Beginners' Guide to Pots)

more unweildy but nice: https://www.bourns.com/pdfs/OnlinePo...erHandbook.pdf
Old 30th March 2019
  #237
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What do you like for patch point jacks that screw to the panel with those knurled nuts, both switched and unswitched? I will be ordering a bunch of them for these mods and some MS-20 mods? Mouser part numbers wouid be awesome.

Thank you.
Old 31st March 2019
  #238
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Quote:
Originally Posted by Bignatius View Post
What do you like for patch point jacks that screw to the panel with those knurled nuts, both switched and unswitched? I will be ordering a bunch of them for these mods and some MS-20 mods? Mouser part numbers wouid be awesome.

Thank you.
cf post 72 if fit under the panel; other types could fit too

knurled nuts should fit on any (same diameter)
Old 31st March 2019
  #239
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Quote:
Originally Posted by Bignatius View Post
What do you like for patch point jacks that screw to the panel with those knurled nuts, both switched and unswitched?
I mostly just use the cheap ones, sold ten or twenty at a time, direct from China, on ebay. I figure most things like that are now made there anyway.

The sort you mostly find have solder tags, with holes in them - which I prefer if i just want to solder wires on directly. They often get listed with the word "PCB" in the title, though I've never seen any that could be PCB mounted, sold that way. They normally come with the knurled round nuts...

Chinese sellers tend to say "PCs" to indicate multiples sold together, e.g. search ebay for 3.5mm mono socket (10pcs,20pcs), and you should find that sort.

It takes a while to get them, of course.

I have bought PCB mounted ones from Thonk, but that's a UK shop, so probably not all that useful to anyone outside Western Europe. They use their own part name ("Thonkiconn"), which probably makes it harder to find an equivalent part number on other sites.... I see they now sell solder tagged ones too:

3.5mm Eurorack Jacks | Thonk - DIY Synthesizer Kits & Components
Old 1st April 2019
  #240
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regarding the jacks...
Space is really tight between the faceplate and the PCB. In order to fit the jacks in I had to bend the loops. I tried several different types of jacks for most of them, the metal was to brittle and broke making soldering the wires a lot of hassle. The only ones I had on hand (out of 5 different types) that worked were cheapies from tayda. There is probably a better option out there, but I want to note that the thonkiconn jacks I have did not work for me.
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