The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Behringer Model D - DIY Mods
Old 17th February 2019
  #181
Lives for gear
Quote:
Originally Posted by macsaif View Post
My comment about LP was concerning the VCF overdrive wether is jt possible to achieve with some modification of Behringer D. I think it is assymeteical distirtion.
For a genuine filter overdrive, you would of course need to actually overdrive the filter input... Mix Out -> an external guitar booster pedal -> Ext In, would seem to be a solution to that, requiring no modification...

- but if you just turn on the Ext In on the mixer without plugging anything into the socket (so it takes it from Audio Out), and turn the level for it all the way up, it's already quite over driven. It might be more useful to put an external attenuator from Audio Out (or maybe MIX Out) to Ext In, for better control of the point where it starts to bite.
Old 19th February 2019
  #182
Here for the gear
As a bit of a noob with DIY synth mod's would it be possible to have a really easy drawing of what wires connect to where..etc
just want to be 100% sure I don't screw up my 'D'
Old 19th February 2019
  #183
Gear Addict
 
Maffez's Avatar
Quote:
Originally Posted by Lorez22 View Post
As a bit of a noob with DIY synth mod's would it be possible to have a really easy drawing of what wires connect to where..etc
just want to be 100% sure I don't screw up my 'D'
hey, any particular mod you're after? some of them are super easy and others need a little attention (sync mod in particular)
Old 20th February 2019
  #184
Here for the gear
Hi Maffez, (thank you for your fantastic work in making these mods possible), I'd like to make a panel with Direct wave outs, 1V/Octave pitch CV output, VCA direct input, 1v/oct pitch CV per VCO, PWM and More noise types , the sync mod looks a bit tricky but maybe I'll do it at a later date.
Old 21st February 2019
  #185
Gear Addict
 
Maffez's Avatar
Quote:
Originally Posted by Lorez22 View Post
Hi Maffez, (thank you for your fantastic work in making these mods possible), I'd like to make a panel with Direct wave outs, 1V/Octave pitch CV output, VCA direct input, 1v/oct pitch CV per VCO, PWM and More noise types , the sync mod looks a bit tricky but maybe I'll do it at a later date.
Cool! & fairly easy

you just need to find which lug of your sockets are tip and which ring. all rings are wired together and grounded (you could even do without that, but it's not a great effort). ground either to gnd on your eurorack rail or the gnd TP on the backside of the boog; if need be you could also stick a female dupont wire to the gnd pin of the boog's eurorack plug or case connector (depending on whether you keep the boog in its case or in a eurorack case)

the tip lugs of your individual sockets are wired to the respective points indicated in the modding guide.

for vca in, if you want the easiest, just connect your input to the point marked on the panel; tad more complicated (maybe for when you find yourself using this mod often enough and confident) is to take out one leg of the yellow cap shown in the guide (desolder the whole thing and put the leg on the vca side back in) and wire tip to tip lug and the connection from the empty whole to normalling lug of your plug (this way the internal vcf-vca connection remains unchanged as longs as no cable is plugged and as soon as you lpug one in, the external vca in is activated) - check trs jack pic below for illustration

et voila!


here's a pic of normalling 3.5 trs jacks

https://cavisynth.com/wp-content/upl...0921561321.jpg

1 = gnd
2 = tip
3 = normal in
Old 21st February 2019
  #186
Gear Addict
 
Maffez's Avatar
oh, and of course put resistors in between where indicated

point on boog ---- cable --- resistor -- lug on jack

(all cableing could alsogo to a little breadboard, which youc could connect to your panel by means of removable connectors (molex or similar)
Old 18th March 2019
  #187
Gear Addict
 

Awesome things going on here. Thanks for the alchemy lab work.

I wonder if that paraphonic mod is somehow usable with midi (without conversion of midi to cv x3 first) or did i get sth wrong and it allready is?

And i didnt clearly get if there is a mod to take full effect of the ADSR for external audio? I think thats not possible stock?
Old 18th March 2019
  #188
Lives for gear
ion-five,

MIDI to CV conversion is a function of the microcontroller, so it can't be made to do anything different, without changing the firmware.

Each envelope only has an output and a trigger - there are two envelopes, and there are sockets to do that on both, already installed. So, you do already have full use of them... but maybe not to do what you want.

Audio doesn't pass through an envelope / ADSR. An envelope just controls something else, like a VCA or a filter.

If you wanted to control the level of audio, and not use the VCOs in the synth, you have a couple of options - either do the VCA In mod, or just feed the audio to Ext In, via the mixer and turn the VCOs off.

If you do it the second way, you don't need to mod it and you also have the use of the filter and filter envelope (aka "contour").

The bit you maybe don't have is a way of triggering the envelopes, at the start of a note. If you can be more specific about what hardware you want to use, and what you want it to do, people might be able to suggest ways of doing it.
Old 18th March 2019
  #189
Gear Addict
 

Yes i meant the amp envelope to shape audio just like and vco.

So paraphonic only with actual cv outputs converted from midi notes outside the synth?
Old 18th March 2019
  #190
Gear Addict
 

I dont have the synth at hand so i dont know if i can get external audio through the shaping EG on stock or if the vca mod opens this possibility?
Idealy pre filter but both options would be great to keep a signal unfiltered
Old 18th March 2019
  #191
Lives for gear
Yes, ion-five, the CPU will still only generate one pitch CV, so you'd need external gear to generate more.

For audio shaping a MIDI controlled external synth, you can send the same MIDI to both, turn off the VCOs in the mixer, and feed the external synth into Ext In. That works without any modifications.

If you don't want the filter to do anything, you could leave it open (set lowest resonance, maximum cut off frequency and set filter Contour Amount to zero). Or, you could do the VCA In mod, bypassing the filter.

For any other external sound to trigger the envelopes, you'd need a level detector, or an envelope follower.

For sending the same MIDI to two synths, you can use a MIDI Through (aka MIDI THRU) box , or just a Y cable. Those tend to work fine if the cables are reasonably short.
Old 18th March 2019
  #192
Gear Addict
 

So the shaping through the EG amp is possible stock? Great and thanks for clarifying, been a while i had an analog synth on hand.
I am asking more to process lets say epiano or similar patches through the ADR of the moog.

I figure most mods really only make sense for modular CV gear around?
I have a one dual LPG left from my modular journey and i think i can even feed its 2 CV ins with stock CV outs of the model D

Sooooo... the mod thta make smost sense without CV gear around it must be still the waveform out/ pwm (vibrato) for self patching stuff like fm?
Old 18th March 2019
  #193
Gear Addict
 

Btw thank you for all your help so far

I just have one more question about the stock path of external audio. Is it possible to feed audio through it without any degradation of sound, so i can quickly get into kind of bypass?

I am trying to find a way to incorporate audio like an vco blofeld style and to see what of all these coold mods help in that approach


Btw can i use the lo and hi outputs in parallel? Because one could be send to tape echo wich would be handy!
Old 18th March 2019
  #194
Lives for gear
Audio shaping should work stock, yes. I think it's possible to get clean audio provided the level isn't too high... I'd have to experiment to make sure.

AFAIK, both Low and High outputs should work in parallel. I'll check soon. Feel free to remind me tomorrow.

The individual wave outputs mod should be useful with just an external mixer, to Ext In, to get different waveforms. PWM with just manual control from a pot (potentiometer) would be useful too, to make a different width pulse waveform. The polyphonic mod could be used to do FM with just pots / passive attenuators, I guess, or maybe a mixer.

I haven't done any of the mods yet, and I'm not going to until my warranty ends, in a few weeks.

If you only want to use the "Loudness Contour" with the VCA, to shape sounds, you could maybe use the filter envelope ("Contour") to drive one of your vactrols, but I'm not sure if it could supply enough current for the LED. You might need a buffer - e.g. an NPN transistor fed via a base resistor, between the negative LED terminal (to the collector) and ground (to the emitter), or make a simple op amp buffer.

I think it would probably be more interesting to apply the filter and filter envelope to the external sound. An amplitude envelope on its own would let you do something like a bowed sound, with slow attack, but applying the filter and filter envelope can do a lot more.
Old 18th March 2019
  #195
Gear Addict
 

Thanks for drawing it out before my visual eye always helpful.

Yes the vactrol can be driven easily i dont think that would be an issue.

I am not sure i completely get your examples:

- mixing a few selected single out waveforms together and sum into external in would be somewhat like a waveshaping oscillator? Could bee cool indeed, but would i need all waveform outs for this or are a few enough?
Also this would be additional to the „clean“ waveforms in the model d mixer? Sounds interesting

- pwm, so instead as in the documentation CV inputs you say a simple pot (per vco?) to the solder point would allow pwm by pot? Wow yeah much better for me without much cv around....uhm....no cv around.

-poly mod, i lost you there. Cant follow how to use a pot there, or you mean only an attenuator that still gets cv in to attenuate? Because again, i suppose a pot would help me more. Or maybe a mix of both, leaving one cv jack for synth internal cv and 2 pots..... but i think i got it wrong...no fm without incoming signal right.


Okay maybe you are right and going the stock way through filter is better to hit the EG but i am not sure i can work subtile that way like from kind of bypass any shaping to shaped. Thats important to me since i use acoustic or kind of realistic sounds



On a sidenote, i am building a transformer color Di box and i wonder if i can take out attenuated DC out of the synth witout sacrifices in patching to (somehow) feed the transformer to taste into saturation
Old 18th March 2019
  #196
Lives for gear
You could, for example, take the saw output of OSC1 as a separate waveform, set the rotary switch to triangle, and connect the new saw output to Ext In. You could then blend that in, making a different shape than the standard "shark tooth" - which is also a blend of triangle + saw, but at a fixed ratio.

I have a modular synth with a Doepfer A-111-3 VCO. That has outputs for triangle, saw and pulse, and I can vary the pulse either with a knob on the VCO, or by voltage control. I use a passive mixer to blend those three parts together, to make more interesting waveforms.

The most you could add to the Behringer Model D is individual waveforms for just that - triangle, saw and pulse, for all three VCOs. You could add any one of those outputs, or all of them, and mix them in via Ext In.

PWM, strictly speaking, means modulating the pulse width. The mod lets you do that, and also lets to control the pulse width with just a variable resistor - or a vactrol. You could use an attenuator feeding a voltage, or you could just use a pot as a variable resistor - which also means you could use a vactrol. There's an LFO CV output you could use too.

With the poly mod, you could take an individual VCO waveform output, run it through an attenuator, and feed it to the control voltage of another VCO, to get some sort of FM.... Exponential FM, I think.

If you need just a bypass switch, why not use an A/B switch, maybe just a passive one, made for guitars?

You could drive your DI safely by using any guitar pedal that has a buffer (not one with "true bypass"), to take the signal from the Boog. For example, all the cheap plastic cased Behringer guitar pedals had a buffer, and most of them are quite clean sounding - so you don't even need to use the effect, just power the pedal and use the buffer.

They don't necessarily all work well for low bass notes though, but they can be improved quite easily, by soldering bigger capacitors in parallel with the input and output ones.

Either of their bass chorus pedals is a good bet - and they're a really good chorus for synths.... There's a BUC400 and a BCH100, I think. I suspect they're exactly the same inside.

Unlike the sort after Juno style one ("Space C"), they made a lot of them, and they were still available new until quite recently. I saw about a dozen of them hanging on the wall of a guitar shop, not long ago, very reasonably priced. There are plenty of used ones on ebay.
Old 18th March 2019
  #197
Lives for gear
Quote:
Originally Posted by ion-five View Post
Okay maybe you are right and going the stock way through filter is better to hit the EG but i am not sure i can work subtile that way like from kind of bypass any shaping to shaped. Thats important to me since i use acoustic or kind of realistic sounds
Your best bet for a clean signal would be to do the full VCA In mod - allowing you to disconnect the signal from the filter. Even so, if you keep the signal level fairly low, so it doesn't clip, and keep the filter open, it could sound quite clean via Ext In.... I will try it at some point, but my idea of clean might not be the same as yours
Old 19th March 2019
  #198
Gear Addict
 

500 kOhm / Sealed Variable Resistor Potentiometer..... are those okay for the PWM poti mod? And maybe suitable for any other mod?
Old 19th March 2019
  #199
Gear Addict
 

Quote:
Originally Posted by AndyHornBlower View Post
Your best bet for a clean signal would be to do the full VCA In mod - allowing you to disconnect the signal from the filter. Even so, if you keep the signal level fairly low, so it doesn't clip, and keep the filter open, it could sound quite clean via Ext In.... I will try it at some point, but my idea of clean might not be the same as yours
Exactly. I am scared of mickey mouse effect. Lets say (extreme stupid example) you run an acoustic piano through there... at least you need to have a setting of a clean pass through.....of course thats silly but the idea


Not really into chorus or effct pedals, a modified cassette deck gets me through tape echo and doubler effect
Old 19th March 2019
  #200
Lives for gear
Quote:
Originally Posted by ion-five View Post
500 kOhm / Sealed Variable Resistor Potentiometer..... are those okay for the PWM poti mod? And maybe suitable for any other mod?
500k is definitely too big to have a useful effect on PWM. I'd have to think about it, for other mods, but probably still too big.

FWIW, Doepfer's site recommends 50k pots, for general attenuators in Eurorack (running on similar voltages, with broadly similar components). In some cases, a smaller value works better. Too small a value could cause problems, but if you look at the section of the schematic the mods relate to, you'll get some idea. Trying one that's too big in value won't hurt anything, but trying one that's too small might.

If you look at page 6 of Maffez's mods document, version 4, you see the part of the schematic that relates to PWM. I'm not clear which point on that diagram is the one he recommends... I'm guessing it's the junction of the 1k resistor with the 7k5 resistor, at the output for the narrowest pulse setting.

Doing anything there with a 500k pot would only have a noticeable effect near one end of its travel. I guess if you used a 10k fixed resistor from that point, (and a diode to keep it below zero volts) you could connect the other end of the resistor to anything from ground to -10V, and see some effect.

So, you could try a 1k to 10k pot wired between ground and -10V, and connect the wiper to that PWM IN point, via, say, a 10k resistor. Maybe add the diode anyway, so it's safe to connect other things later.

You could try a bigger fixed resistor first. I'd expect a more subtle effect on the pulse width. You could maybe try a smaller one, but I wouldn't go below 1k, without thinking about it some more. A bigger vale is safer; a smaller value is likely to be more effective.

If the pot value is too big, the response curve will seem strange - not linear, with all the changes happening near one end of its travel.

Whatever size pot you choose, it will behave the same at the two end points - only the size of the fixed resistor, between the pot and the PWM IN point, matters there.

Once you've chosen a fixed resistor, any pot value is safe, but a smaller value will draw more current from the supply. 500k definitely is too big, and would behave almost like a switch, at one end of travel. 50k might be okay. I would guess 10k, or even 5k, would be better, for that purpose, but you could try 50k first.
Old 19th March 2019
  #201
Lives for gear
Quote:
Originally Posted by ion-five View Post
Not really into chorus or effect pedals, a modified cassette deck gets me through tape echo and doubler effect
I don't like the fast chorus effect, that guitarists sometimes use, but if you set a chorus on a very low rate, it gives the impression of detuned VCOs - or more VCOs than you actually have.

It's an easy way to get a pseudo stereo effect from a mono synth too. There are two outputs on the BUC400/BCH100, one of which is fairly clean, the other carrying the chorused sound. If you treat it as a stereo output, it's reasonably convincing.

It doesn't really matter what effect pedal you use though, so long as there's no "true bypass" option. You probably wouldn't damage the synth connecting it to your DI directly, but if there's a buffered pedal in between, that eliminates any chance.

Any preamp that can handle the output from the synth would be fine too.
Old 19th March 2019
  #202
Gear Addict
 

Understood most of it hehe....will try around 30-50k variable resistor then
@ Maffez could you clarify pwm point for potentiometer?

And one generel question. All mentioned grounding wires go to one case ground destination? Will be quite spagetthi in there?
Old 19th March 2019
  #203
Gear Addict
 

I see what you mean, i look from exactly the other side. Tape and synth can do most effects by themself.

I think you got the transformer DI thing maybe different then i meant. I do that ultimately for effect. I have some vintage UTC and allready heraded the effect on drums pretty good even with laughable monitoring. I got a second one now and try to think ramping it up and down again so 1:1 on both ends....but since they are only up to 500 ohm that would force me to low ohm input.
When i tried the one on hand it was fed by modular level and i assume maybe dc helped with driving it, so i think about putting a little cv jack to the DI for attenuated CV.
The stock DI has a 10:1 xformer and i am not sure if implementing it with my 2x 500:500 ones or pull it out. (Again aim is driving the utcs to taste) any idea?



Oh you meant by current of the transformers i could damage the model D? Ough...

And then back to topic i think (sry Maffez)
Old 19th March 2019
  #204
Lives for gear
Quote:
Originally Posted by ion-five View Post
All mentioned grounding wires go to one case ground destination? Will be quite spagetthi in there?
As far as I know, there's only one ground plane - not separate digital and analog grounds. The digital part is quite small anyway; just the CPU and other parts near the MIDI sockets.

The large flat looking areas you see on the underside of the PCB are the ground plane. You'll find plenty of legs of "through hole" components, soldered to it, e.g. the outer pins of each 3.5mm CV socket.

Good practice, for anything with audio, is "star grounding", which means just picking one point as ground, and making all connections to there. You could do that, if you find something chunky looking to connect to, or you could just run ground wires to any convenient point, when you do each mod, and hope for the best.

The worst that can happen is a ground loop / hum antenna effect - you can always rethink it, if that happens.
Old 19th March 2019
  #205
Lives for gear
Quote:
Originally Posted by ion-five View Post
Oh you meant by current of the transformers i could damage the model D? Ough...
Yes, if the impedance of the transformer is quite low, the current could be a problem. There's also "back EMF" to worry about - coils kick back, when you take a voltage away. As the magnetic field collapses, it causes a current to flow in the coil, in the opposite direction from the current that was driving it before.

So, personally, I wouldn't drive a transformer DI directly from the output of a synth. I'd use a buffer, as a condom. Preferably, a fairly cheap one, like a used guitar pedal - but the buffered bypass sort, not one with "true bypass".
Old 19th March 2019
  #206
Gear Addict
 

Now i got it, thanks for the warning!
Yes its variable from 150 to 500ohm.
I suppose some buffer directly at the Di for general condomness would be best . would be more elegant but not sure if theres a simple way to implemet it to the DI or Jack.
Or would a 500ohm „face „ be definitely safe?

I cant see the ground planes. I assume a grounding screw in the case is either present or would work out fine!?
Old 19th March 2019
  #207
Lives for gear
I've attached part of one of Maffez's labelled pictures of the underside of the PCB.

All of the blank, featureless, yellow areas are the ground plane. Along the bottom of this picture, you can see the pins for the 3.5mm jack sockets - each one has four pins.

The pin on the outside edge (bottom of the picture) is connected to ground, so those would be an easy place to solder to, but it might be best not to keep soldering on more wires to the same socket... It looks like both of the outer two pins on each socket are ground.

If you have a meter with continuity (e.g. one that beeps), put one probe on one of those, and look for other points that are connected.
Attached Thumbnails
Behringer Model D - DIY Mods-cv-jacks-etc.jpg  
Old 19th March 2019
  #208
Gear Addict
 
Maffez's Avatar
hey fellas - so nice you're keeping at it & good info!

about pwm mod point, see pic. i just used the pin of the rotary switch. remember using a 500k poti for its switch-like behaviour atthe end of its travel, as andy cleverly pointed out, because i liked it that way. in the meantime i just use input jacks and use external cv from my modular. but yes, smaller values are more useful. when ordering pots for the first time maybe make sure to get some variety of values to experiment with (10k, 47k, 100k, 250k, or so)

and oh: hi/lo outputs work in parallel
Attached Thumbnails
Behringer Model D - DIY Mods-wf.jpg  
Old 19th March 2019
  #209
Gear Addict
 

Not sure what you meand with additional 500k

I would take a 25k one now and try

The pwm 1 mark is the solder point for the pot? Okay

Last edited by ion-five; 19th March 2019 at 11:56 AM..
Old 19th March 2019
  #210
Gear Addict
 
Maffez's Avatar
Quote:
Originally Posted by ion-five View Post
Not sure what you meand with additional 500k

I would take a 25k one now and try

The pwm 1 mark is the solder point for the pot? Okay
Yup & keep us posted how it goes!

Sorry for the 500k; that's another mod (the boogdrive) - wrote pre coffee this morning.

For pwm 25k pot (and, if desired, 1-2k resistor for protection) should sort you out!
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump