DTA (Discrete VCA) - Next Module Up From Manhattan Analog

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negativspace
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DTA (Discrete VCA) - Next Module Up From Manhattan Analog

Post by negativspace » Thu Mar 22, 2018 4:28 pm

Alright, after way too long a wait this thing is finally ready. DTA stands for Discrete Transistor Amplifier and the module itself is a riff on the classic Minimoog VCA. (I know it's not the most imaginative name, but there's only so much room for text on these 4hp panels. :hihi: )

This was originally part of the 3-section discrete monosynth backend I designed a few years ago. The other two sections have been made available as the DTM and Discrete SVVCF, of course. With this, the signal chain can finally be completed.

If you'd like an audio demo to whet your appetite, the SVVCF demo on my Soundcloud (embedded below) was recorded with that original backend prototype and from the 2:24 mark until the end the VCA is on display. (The first 2:23 was recorded straight from the VCF out.) It should give you an idea of the way this thing sounds when overdriven a bit, but it won't really help with displaying the clean behavior that it is most certainly capable of. We'll get there - the prototype is only 24 hours old. Early days.

I have another round of prototyping to do before I can order this one, the first layout needed a couple tweaks as did the panel, but there's no reason it shouldn't be available by the end of April, give or take a week or two. It will also be available as a DIY project as usual.

http://soundcloud.com/negativspace/discrete-svf-test-01


A link to the DIY thread for builders is HERE

Image
Last edited by negativspace on Tue Sep 25, 2018 4:08 pm, edited 4 times in total.

Futuresound

Post by Futuresound » Thu Mar 22, 2018 5:11 pm

YES!

I love my DTM, and every time I use it I think 'I wish this was a VCA too'!

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lasesentaysiete
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Post by lasesentaysiete » Thu Mar 22, 2018 5:42 pm

sounds great!

regarding knobs:

volume is initial gain, cv is an attenuator, and drive is drive?

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Post by basicbasic » Thu Mar 22, 2018 5:51 pm

Love it!

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Post by negativspace » Thu Mar 22, 2018 6:28 pm

lasesentaysiete wrote:sounds great!

regarding knobs:

volume is initial gain, cv is an attenuator, and drive is drive?
In practice, sort of? "Drive" is a simple input attenuator. At higher settings the audio input can really overdrive the module, depending on its amplitude obviously.

From there it gets a little bit more interesting. This isn't one VCA, it's two in series and you have to open both of them to get any output. "CV" is the control signal input for the first stage, "volume" is the control signal input for the second stage. Both controls have +V normalled through the jacks so you can still open the VCA(s) without any external inputs.

In the original, "CV" was the hardwired Contour Generator (EG) input and "volume" was an input for an external expression pedal. In the modular context it could be used for a velocity signal pulled from a MIDI>CV converter or step sequencer, a joystick, ribbon controller, expression pedal, etc. It could also be used simply as a second CV layer for any signal you want to throw at it... or you can just forget about it, leave the jack empty, and use that knob as a master volume control.

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Post by Hi5 » Thu Mar 22, 2018 6:41 pm

Very nice. Perfect for accented voices
tetno: https://soundcloud.com/richard-holhburn
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Re: DTA (Discrete VCA) - Next Module Up From Manhattan Analo

Post by Joe. » Thu Mar 22, 2018 6:45 pm

negativspace wrote: It will also be available as a DIY project as usual.
Will it have 10,000 parts like a discrete Op-Amp?

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Re: DTA (Discrete VCA) - Next Module Up From Manhattan Analo

Post by alanza » Thu Mar 22, 2018 7:10 pm

LoFi Junglist wrote:
negativspace wrote: It will also be available as a DIY project as usual.
Will it have 10,000 parts like a discrete Op-Amp?
likely no: the MS20's VCA has been described as "just a transistor", so I think the source of the character in this module is likely to also be its relative simplicity
"I always thought that the DX was potentially a warm instrument... Lots of people felt otherwise." —Dave Bristow

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Re: DTA (Discrete VCA) - Next Module Up From Manhattan Analo

Post by negativspace » Thu Mar 22, 2018 7:19 pm

LoFi Junglist wrote:
negativspace wrote: It will also be available as a DIY project as usual.
Will it have 10,000 parts like a discrete Op-Amp?
Nope, it all fits on a board roughly the same size as the DTM. 9 transistors, a few caps, and ~25 resistors. Still settling on a final layout.

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Post by Azarius » Thu Mar 22, 2018 7:21 pm

Futuresound wrote:YES!

I love my DTM, and every time I use it I think 'I wish this was a VCA too'!
I totally agree! Love the character of the DTM... this is going to be great!

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Post by lohacker » Fri Mar 23, 2018 6:01 am

like the sound and was looking for a two inputs vca, well done! :tu: :party:

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Post by droningspaghettimonster » Fri Mar 23, 2018 6:23 am

MA are the best!

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Post by matttech » Fri Mar 23, 2018 1:40 pm

lohacker wrote:like the sound and was looking for a two inputs vca, well done! :tu: :party:
Definitely interested in this. Not sure it has two inputs though does it?

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Post by lohacker » Fri Mar 23, 2018 2:11 pm

matttech wrote: Definitely interested in this. Not sure it has two inputs though does it?
Well, technically there are 2 vcas with an input each (Vol and CV), if I didn't misread this post
negativspace wrote: From there it gets a little bit more interesting. This isn't one VCA, it's two in series and you have to open both of them to get any output. "CV" is the control signal input for the first stage, "volume" is the control signal input for the second stage. Both controls have +V normalled through the jacks so you can still open the VCA(s) without any external inputs.

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Post by matttech » Fri Mar 23, 2018 3:28 pm

Aha! It sounds like a similar idea to the ajh synth minimod vca in that case, which would make sense if they are both based on moog designs

I think the idea behind their one is that the first CV shapes your sound via envelopes in the usual way, and the second (master) one was for overall pedal control

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Post by joem » Fri Mar 23, 2018 3:45 pm

I'm definitely interested in this. Coincidentally, I just got a DTM pcb and panel a few days ago that I'm planning to build this weekend.

Do the Volume and CV controls have different characteristics? For instance, if you turn Volume up and voltage-control CV, does it sound different than turning CV up and voltage-controlling Volume? I haven't played around with VCAs in series before, so I'm not sure if the order changes things.

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Post by ugokcen » Fri Mar 23, 2018 4:07 pm

Looking forward to this, any idea when it will hit the stores?

The two cv controls mean that you can keep a constant amount of saturation and add accents for volume or keep a constant volume and add saturation as accents, am I getting this right?

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Post by negativspace » Sat Mar 24, 2018 6:46 am

joem wrote:Do the Volume and CV controls have different characteristics? For instance, if you turn Volume up and voltage-control CV, does it sound different than turning CV up and voltage-controlling Volume? I haven't played around with VCAs in series before, so I'm not sure if the order changes things.
On a circuit level the two stages are slightly different, but in practice I doubt you'd ever notice. As long as both are open you'll get sound, and it's not real picky about how or in which order.
ugokcen wrote:Looking forward to this, any idea when it will hit the stores?

The two cv controls mean that you can keep a constant amount of saturation and add accents for volume or keep a constant volume and add saturation as accents, am I getting this right?
I'm hoping it'll be out by the end of April, give or take a week or two. From here it's just a matter of fixing three minor board errors, verifying with another prototype, and then gathering parts while the production PCBs and panels are manufactured. I've done enough of these 4hp designs that they happen rather quickly once I get them working.

The saturation happens at the input, so yes, you can set the timbre as you like it with the 'drive' control and the VCA modulation/output level won't mess things up.

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Post by negativspace » Tue May 08, 2018 1:34 am

Alright, finally some news on this project. :party:

I've managed to nearly hit my mark on release timing - PCBs and panels have been ordered, delivery expected by the end of the month. I should have DIY sets available in my shop by June 1 and built units a couple days after. They'll start appearing at retailers - starting with Analogue Haven - as soon as I can get some built and shipped.

I'm really pleased with this one and excited to get them out there. Won't be long now!

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Post by negativspace » Thu May 17, 2018 3:48 pm

One down... PCBs have a shorter lead time than panels, so the boards are here. I suppose anyone who wants a PCB-only version of this thing can go ahead and order, effective immediately. I'll update my web shop by the end of the day to reflect that option.

Panels should be here soon, and then we're set for the rollout.

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Post by zed888 » Fri May 18, 2018 4:52 pm

Will there be kits available from you or elsewhere?

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Post by sempervirent » Fri May 18, 2018 6:03 pm

Very cool, great to see a new MA release.

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Post by negativspace » Fri May 18, 2018 6:29 pm

zed888 wrote:Will there be kits available from you or elsewhere?
If you mean full kits with components, that's mostly up to Thonk/Synthcube/Modular Addict. Generally speaking I don't do full kits. But I'm usually willing to put them together if you pester me through PM or email, so... :hihi:
sempervirent wrote:Very cool, great to see a new MA release.
:party:

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Post by cackland » Fri May 18, 2018 6:53 pm

Interested in this too :)

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Post by ben_hex » Sat May 19, 2018 1:35 pm

Great to see this negativspace. To be picky leaving volume open and cv over drive would have bee; my choice. That way velocity or accents can provide a tonal / saturation change as well as have the volume under cv control. I’m familiar with the VCA and the two VCA method from the Minimoog though and love your DTM mixers. So I’m definitely in for this one :party:
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