Doepfer A-133-2 Mod Input uses?

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nomenklature
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Doepfer A-133-2 Mod Input uses?

Post by nomenklature »

Hi -- I'm thinking about getting the Doepfer A-133-2 Dual Voltage Controlled VCA / Polarizer / Inverter / Ring Modulator and was wondering what exactly the Mod input does, and how you use it.

Is it just another way to control the signal level being sent through the VCA, in addition to the manual knob and the regular CV input?

The manual says: "In addition the CV signal can be modulated via the modulation control input Mod by means of another control voltage. The Mod socket is normalled to + 5V, ie a constant positive voltage is used as modulation CV provided that no plug is inserted into the Modsocket. The control voltage range for this socket is bipolar and can be adjusted to the user's requirements by means of a trimming potentiometer. The factory setting is -5V ... + 5V (ie -5V no modulation, 0V about 50% modulation, + 5V full modulation)."

thanks
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authorless
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Re: Doepfer A-133-2 Mod Input uses?

Post by authorless »

Sounds like it is a VCA that controls the level of CV input.
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helix
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Re: Doepfer A-133-2 Mod Input uses?

Post by helix »

It is to polarize the signal
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Re: Doepfer A-133-2 Mod Input uses?

Post by flashheart »

helix wrote: Tue Feb 09, 2021 4:33 pm It is to polarize the signal
No, the main CV input does that (like on the original A133), the mod input controls the amount of CV. Confusingly the mod input CV range is -5v to +5v with -5v being zero modulation (though apparently this can be changed). You could use that input for conventional VCA duties with no CV in the main CV.
I'm not buying a maths though, not my idea of fun...
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Re: Doepfer A-133-2 Mod Input uses?

Post by nomenklature »

thanks for these replies! helpful. this module seems quite useful and underrated.
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Re: Doepfer A-133-2 Mod Input uses?

Post by R.U.Nuts »

flashheart wrote: Tue Feb 09, 2021 5:30 pm
helix wrote: Tue Feb 09, 2021 4:33 pm It is to polarize the signal
No, the main CV input does that (like on the original A133), the mod input controls the amount of CV. Confusingly the mod input CV range is -5v to +5v with -5v being zero modulation (though apparently this can be changed). You could use that input for conventional VCA duties with no CV in the main CV.
Wow that's a really neat feature but after reading the manual I think MOD only affects the CV and not the manual control. This means you can patch a conventional VCA by plugging a positive constant voltage into the CV input and modulating this with a CV at the MOD input.
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Re: Doepfer A-133-2 Mod Input uses?

Post by dip_registered »

Have you guys got this module? It doesn’t seem popular but it looks really powerful

I read this review and wondered if people felt the same?

The centre point (0) of the manual knobs are not near the middle. They are at ~ +0.7. To rotate them visually 'in the middle', you need to use the dual light LED for that.
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Re: Doepfer A-133-2 Mod Input uses?

Post by woetjo »

dip_registered wrote: Wed Apr 21, 2021 11:36 pm Have you guys got this module? It doesn’t seem popular but it looks really powerful

I read this review and wondered if people felt the same?

The centre point (0) of the manual knobs are not near the middle. They are at ~ +0.7. To rotate them visually 'in the middle', you need to use the dual light LED for that.
Yes, I have this module. I bought it pimarily to use as a two channel attenuverter but it turns out to be an awesome multifunctional little module.

I experienced the same issue with the zero center point being somewhat off at +0.7. I though it was a manufacturing error but you seem to have the exact same problem.

And what is up with the faceplate 9 o’clock position numbering for the manual pots? It says ‘2’ but should read ‘-3’. Right?
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Re: Doepfer A-133-2 Mod Input uses?

Post by wonkychris »

This is looking like a great module in 4hp. I suppose it is very similar to Make Noise ModDemix but without the mixing of channels onboard?

Anyone using this much yet? I can't see any demos on YouTube
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Re: Doepfer A-133-2 Mod Input uses?

Post by transistorresistor »

It is similar to moddemix wo the mixing but doesnt sound anything like it, it is much much cleaner sounding in comparison. I have both and usually reach for the doepfer first, fantastic module.
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Post by Gordon Cole »

woetjo wrote: Sun Aug 15, 2021 1:47 am And what is up with the faceplate 9 o’clock position numbering for the manual pots? It says ‘2’ but should read ‘-3’. Right?
So funny, I hadn't noticed that. Apparently neither did anyone else!!
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wonkychris
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Re: Doepfer A-133-2 Mod Input uses?

Post by wonkychris »

transistorresistor wrote: Sun Jan 09, 2022 12:14 pm It is similar to moddemix wo the mixing but doesnt sound anything like it, it is much much cleaner sounding in comparison. I have both and usually reach for the doepfer first, fantastic module.
OK thats great thanks. I only plan to use it for CV (DC) so not worried about the nice grimy sound from ModDemix. Clean is better for me!
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Re: Doepfer A-133-2 Mod Input uses?

Post by mandarinpile »

woetjo wrote: Sun Aug 15, 2021 1:47 am
dip_registered wrote: Wed Apr 21, 2021 11:36 pm Have you guys got this module? It doesn’t seem popular but it looks really powerful

I read this review and wondered if people felt the same?

The centre point (0) of the manual knobs are not near the middle. They are at ~ +0.7. To rotate them visually 'in the middle', you need to use the dual light LED for that.
Yes, I have this module. I bought it pimarily to use as a two channel attenuverter but it turns out to be an awesome multifunctional little module.

I experienced the same issue with the zero center point being somewhat off at +0.7. I though it was a manufacturing error but you seem to have the exact same problem.

And what is up with the faceplate 9 o’clock position numbering for the manual pots? It says ‘2’ but should read ‘-3’. Right?
From what you are saying it sounds like it doesn't have center indent pots. Am i right?

I was hoping it has, because everything else about this module sounds really great and I am considering getting several for all the different things it can do. And the price is right. But trying to find the center position without an indent can be a chore. Does the LED help? the LED represents the output voltage, correct? So if at that particular moment the input is seeing 0v the LED will be off and will not be useless for finding the center position.

I have A-141-2 VCADSR which has polarizers knobs on CV inputs for envelope stages. The same thing as with A-133-2: It is a fantastic module except for the fact that it doesn't have center indents on those 4 polarizer pots.
My A-138e quad crossfader on the other hand has center indents. And the center is off a little bit on all 4 subunits (see the picture with all knobs in center position), but it doesn't matter to me much, because I can easily feel when I have reached the center position.

Does anyone have an idea if the A-133-2 (and A-141-2 for that matter) can be moded with center indent pots?
271433966_655925295591888_9010291330766347064_n.jpg
transistorresistor
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Re: Doepfer A-133-2 Mod Input uses?

Post by transistorresistor »

The A-133-2 doesnt have center detent pots and for good reason, as you are already experiencing on your 138. I recently posted this in a different thread:

some general thoughts on center detents, it is *very* difficult for most potentiometer manufactures to have a center detent w tolerances that will reliably work for a circuit that has zero null. If you got a bipolar control and the detent was on one side or the other of where you need it to null, which it almost is guaranteed to be if its made by any company in business today, it could be especially maddening trying to hit the null. Manufacturer is doing you a giant favor by putting a regular pot on there so the user can *absolutely* null it out. Not so much fun searching for the null in use but this is not a part that manufacturers are deciding not to buy and install, its a part that is extremely challenging for the pot factory to make on the lines they run for the prices the pots cost. If one was committed to using a detent pot on a circuit like this I personally would expect to reject a huge qty of pots in assembly in order to make the circuit work unless I was able to secure an unusually accurate batch of pots which does not my reflect my experience at all. Just some food for thought. For sure I agree that a detent to null would be wonderful, but this is kinda one of those parts that many people dont realize is a unicorn.
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mandarinpile
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Re: Doepfer A-133-2 Mod Input uses?

Post by mandarinpile »

transistorresistor wrote: Fri Jan 14, 2022 12:54 pm The A-133-2 doesnt have center detent pots and for good reason, as you are already experiencing on your 138.
Thanks for the input. I was suspecting the situation with the detent pots to be something like this.

However, the a-138 is actually the good example here. Maybe i didn't make it clear. The detent is not physically in the center, but it is at the null point of the control. I am getting silence when the pot is the detent position. It is visually a bit off-puting, but so easy to perform with - when i need silence i just turn the knob until I feel the detent.

So why can a-138 have center detent pots that work as expected, but not other modules. The relativly low price of a-138 tells me Doepfer didn't hand select exceptionally precise parts.

Any other input would be greatly appreciated. I will also look up the thread you reffered to.
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Re: Doepfer A-133-2 Mod Input uses?

Post by transistorresistor »

looking more closely at this, the 138e uses a 4 terminal tapped pot so this is not a fair apples to apples comparison and my comments regarding standard inexpensive 3 terminal pots w center detents dont necessarily apply here. It appears that the 133-2 and the 138e are using different pots all together. I dont have one of those to look at closely so I should refrain on commenting further cause I dont want to publish bad information. Only thing I'll add is that if the shaft isnt keyed to the panel (likely isnt) you can remove the knobs, loosen the nut, and center the shafts so your detents line up at noon if its setting off your OCD.
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mandarinpile
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Re: Doepfer A-133-2 Mod Input uses?

Post by mandarinpile »

transistorresistor wrote: Fri Jan 14, 2022 3:05 pm looking more closely at this, the 138e uses a 4 terminal tapped pot so this is not a fair apples to apples comparison and my comments regarding standard inexpensive 3 terminal pots w center detents dont necessarily apply here. It appears that the 133-2 and the 138e are using different pots all together. I dont have one of those to look at closely so I should refrain on commenting further cause I dont want to publish bad information. Only thing I'll add is that if the shaft isnt keyed to the panel (likely isnt) you can remove the knobs, loosen the nut, and center the shafts so your detents line up at noon if its setting off your OCD.
Thank you for your input once again, transistorresistor. At least i understand now that utilizing center detent pots in module design is much more complicated than I imagined.

And back to the main topic - mod input uses.
I find this input very promising for my setup. I have a fader bank that i use for performances. With this i will be able set the vca in motion, so to speak, with faders. The mod input is like a vca for the cv for the main vca/polarizer. Brilliant :). I keep on returning to Doepfer because of modules like a-133-2
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