Alisa 1387 filter / 1377 waveshaper project

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BARD
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Alisa 1387 filter / 1377 waveshaper project

Post by BARD » Mon Jul 27, 2020 2:25 pm

Hi all

IMG_20200723_223044a.jpg
Long story short, I've serviced this beauty recently - It's Alisa 1387, monophonic synth from Luberetskiy factory. This specimen is from 1987.
1387 is still pretty obscure. That's shame, since it does have rather nice sounding circuitry. I have discovered that the filter could be easily reproduced using common parts, hence this project.

For interested here's more technical info:
http://www.ruskeys.net/eng/base/alisa1387.php

The filter is resonant 12dB lowpass with positive feedback and exponential tracking:
alisa1387-c.PNG
alisa1387.PNG
This differs significantly from Moog ladder filter. It's like between Synthacon and Moog - Using diode currents to filter out sound, but doing it in differential pairs.

I guess there will be some interest on adapation to Eurorack, so I'll slowly post progress updates.

Feel free to use this schematic to build your own copy. I would use standard matched NPNs (original use matched pair DIP ICs) and 741 op-amps (can do with single TL072 as well).

Btw, it's mess inside.
IMG_20200724_113654.jpg
IMG_20200724_113803_1a.jpg


What do you think about it?
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Last edited by BARD on Thu Jul 30, 2020 12:06 am, edited 1 time in total.

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Isaiah
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Re: Alisa 1387 filter project

Post by Isaiah » Mon Jul 27, 2020 5:40 pm

Watching this thread with great interest!

Is the intention that you will develop PCBs for this?
If so, a few polite suggestions/requests:
1. Please include PCB mounting holes so that those of use who don’t build Eurorack can still
Mount the PCB parallel to the panel.

2. The addition of the 1387’s (or 1377’s) VCA would be a good if it isn’t too much of a headache for you. When porting a monosynth’s VCF to modular it’s always nice to have the original VCA available too.
The Manhattan Analog MA35 (Korg MS-10 VCF+VCA) is a good example of this.

3. The 1377’s waveshaper is cool. Maybe just make a 1387/1377 mashup voice module for Eurorack/standalone? I’m half joking haha!

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BARD
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Re: Alisa 1387 filter project

Post by BARD » Mon Jul 27, 2020 6:52 pm

Yep, this probably will be Euro / MOTM kit. The addition of the VCA is a good idea. Only filter / VCA this time, entire voice would devour too much time...

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Re: Alisa 1387 filter project

Post by Tonescape » Tue Jul 28, 2020 1:38 am

Interesting 🙂
Will be following this thread.

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Re: Alisa 1387 filter project

Post by Isaiah » Tue Jul 28, 2020 7:26 am

BARD wrote:
Mon Jul 27, 2020 6:52 pm
Yep, this probably will be Euro / MOTM kit. The addition of the VCA is a good idea. Only filter / VCA this time, entire voice would devour too much time...
Great! A fairly compact PCB with mounting holes in the corners and maybe overlapping Eurorack and MOTM PSU connection footprints would ensure that it would work well in a variety of formats.

I understand. I was just teasing ha! But possible future projects... a VCO? A dual EG? LFO/Noise/Slew or something like that?
A Soviet synth voice realised as 4 or 5 modules. Wishful thinking ha!
Anyway, I'm very keen to see how this turns out!
Last edited by Isaiah on Tue Jul 28, 2020 11:35 am, edited 2 times in total.

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Re: Alisa 1387 filter project

Post by Isaiah » Tue Jul 28, 2020 7:29 am

I forgot to ask, does the VCF self-oscillate?
How is the key tracking?

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Re: Alisa 1387 filter project

Post by BARD » Tue Jul 28, 2020 4:34 pm

Isaiah wrote:
Tue Jul 28, 2020 7:26 am
Great! A fairly compact PCB with mounting holes in the corners and maybe overlapping Eurorack and MOTM PSU connection footprints would ensure that it would work well in a variety of formats.
The boards are designed with thought of making Euro kits, but they will fit nicely if mounted parallelly to panel in 5U builds (If 2U panel width is used). There are 4 mounting holes used to hold rear masking plate that can be utilized in 5U build. Power connector is combined Euro / MOTM.
Just spent last 8 hours making layout since the breadboard prototype works nicely 8-)
alisa_proto.jpg
asdf.png
Besides the motherboard there is also an Eurorack interface board consisting of three LED drivers (serving as overdrive indicators) and Accent generator circuitry. The Accent works by accepting trigger or control voltage on its attenuated input, adding decay tail to it and applying that processed voltage to resonance amount and VCA CV simultaneously. I've thought that functionality will blend nicely with filter character.
Isaiah wrote:
Tue Jul 28, 2020 7:26 am
I understand. I was just teasing ha! But possible future projects... a VCO? A dual EG? LFO/Noise/Slew or something like that?
No plans for any single-synth series. Already made transformer ring mod, 303 oscillator and Korg Poly-800 filter in this visual style.. I just make those circuits that resonates with me :hihi:
2069.jpg
Isaiah wrote:
Tue Jul 28, 2020 7:29 am
I forgot to ask, does the VCF self-oscillate?
How is the key tracking?
Yep, and inherent ladder distortion is clipping resonant wave softly. I have modified feedback circuit so the response of the potentiometer is ~anti-log (in original design nothing changes until the pot is cranked to 70% travel, here the audible resonance kicks in at 20% travel, and last 10% is self-oscillation). Key tracking is not bad for two transistor exponential converter without scaling compensation, it tracks V/Oct within 200Hz - 1.5kHz range, but don't be tempted to use it as audio oscillator.
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Re: Alisa 1387 filter project

Post by Schlumpfhut » Wed Jul 29, 2020 4:58 am

Great project so far.
I will add this filte to my "shut up and take my money" list of future PCB projects both Euro and 5U

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Re: Alisa 1387 filter project

Post by maltemark » Wed Jul 29, 2020 5:49 am

Very interested
Feel free to use my old samplepacks: https://freesound.org/people/altemark/
--

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Re: Alisa 1387 filter project

Post by socom93 » Wed Jul 29, 2020 3:27 pm

Really interested too !!!!!
Thank you for bringing back russian synths !

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by BARD » Thu Jul 30, 2020 12:07 am

Great to see interest in those machines!

Waveshaper seems easy-peasy too, so I guess there will be another module..
alisa1377_ws.PNG
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Re: Alisa 1387 filter / 1377 waveshaper project

Post by Isaiah » Thu Jul 30, 2020 2:20 am

Good work!

Accent sounds like an interesting feature.
If a builder only wanted to use the main circuitry PCB, not the Eurorack control PCB, what functionality would be lost?
LED drivers and Accent circuitry?
Would it also require input summing resistors to be wired off-board?
I don’t know how final your PCB layout is yet, but I wonder if there is the possibility to either migrate all the circuitry from the control PCB, or reduce size of the main PCB.
If the main PCB’s width is an integer multiple of 1”/2.54mm and the mounting holes are 0.3” from the edges that would make it much more easily mounted in a boat of Serge/CGS PCBs too.
Just a thought...

BP input looks like an interesting addition!

Would you mind pointing out where the VCA is on the 1387 schematic please? Maybe I’m being silly but I can’t find it.
It looks like there might be two full-wave rectifiers (I think) linked to the VCO.
Can you give some insight into what they’re for please?
Saw-Triangle shaping and then an octave up Triangle?

Glad you’re looking at the 1377’s waveshaper!

Thanks for working on these projects!

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by BARD » Thu Jul 30, 2020 5:52 am

Isaiah wrote:
Thu Jul 30, 2020 2:20 am
If a builder only wanted to use the main circuitry PCB, not the Eurorack control PCB, what functionality would be lost?
LED drivers and Accent circuitry?
Yep, LED drivers and Accent circuitry. Some mixing / attenuating is also done on control PCB.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Would it also require input summing resistors to be wired off-board?
Not really, but attenuating potentiometers (if needed) has to be wired to input jacks offboard.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
I don’t know how final your PCB layout is yet, but I wonder if there is the possibility to either migrate all the circuitry from the control PCB, or reduce size of the main PCB.
I thought about that, but in either option board becomes too crammed.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
If the main PCB’s width is an integer multiple of 1”/2.54mm and the mounting holes are 0.3” from the edges that would make it much more easily mounted in a boat of Serge/CGS PCBs too.
Just a thought...
Sorry, too late for this already, but I'll pay attention to this if I'll make any other kits soon!
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Would you mind pointing out where the VCA is on the 1387 schematic please? Maybe I’m being silly but I can’t find it.
There isn't VCA in this schematic. It's just standard current controlled differential transistor pair + opamp, nothing special here. Will post the schematic when BOM gets an update.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
It looks like there might be two full-wave rectifiers (I think) linked to the VCO.
Can you give some insight into what they’re for please?
Saw-Triangle shaping and then an octave up Triangle?
Can't understand what part of the circuit you mean. In case of snippet from original schematic - those square blocks are representing operational amplifiers used in amp/feedback part of the filter, it's just Russian notation.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Glad you’re looking at the 1377’s waveshaper!
Yeah, I probably will come with the board designs tomorrow. Those waveshapers are nothing esoteric, yet still sounding pretty nice. Mine would come little stripped off options, but significantly smaller than SSSR Labs SM630 AWS - such single option would benefit much from slimming ;)

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by Isaiah » Thu Jul 30, 2020 6:57 am

BARD wrote:
Thu Jul 30, 2020 5:52 am
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
If a builder only wanted to use the main circuitry PCB, not the Eurorack control PCB, what functionality would be lost?
LED drivers and Accent circuitry?
Yep, LED drivers and Accent circuitry. Some mixing / attenuating is also done on control PCB.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Would it also require input summing resistors to be wired off-board?
Not really, but attenuating potentiometers (if needed) has to be wired to input jacks offboard.
That should be fine. I think lots of non-Eurorack builders are used to wiring input sockets and potentiometers off-board.
The issue would be if the input summing resistors had to be soldered off-board too.

BARD wrote:
Thu Jul 30, 2020 5:52 am
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
I don’t know how final your PCB layout is yet, but I wonder if there is the possibility to either migrate all the circuitry from the control PCB, or reduce size of the main PCB.
I thought about that, but in either option board becomes too crammed.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
If the main PCB’s width is an integer multiple of 1”/2.54mm and the mounting holes are 0.3” from the edges that would make it much more easily mounted in a boat of Serge/CGS PCBs too.
Just a thought...
Sorry, too late for this already, but I'll pay attention to this if I'll make any other kits soon!
Ah, that's a pity but nevermind. Out of interest, how wide (HP) will the module be?
Yeah, CGS PCBs (with only a few exceptions) are integer multiples of 1" wide and 6" tall.
Obviously 6" is too tall for Eurorack, but it your future PCBs positioned the mounting holes at (n x 1")+0.7" horizontally and vertically it might allow Serge/CGS builders to include your PCBs in a Serge build a bit easier if they used this PCB:
http://www.synthpanel.com/modules/cgs120_rail.html
That might be a lot of work to maybe only gain just a few extra users, I don't know... Might be easy to accommodate or might not be worth the trouble.

BARD wrote:
Thu Jul 30, 2020 5:52 am
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Would you mind pointing out where the VCA is on the 1387 schematic please? Maybe I’m being silly but I can’t find it.
There isn't VCA in this schematic. It's just standard current controlled differential transistor pair + opamp, nothing special here. Will post the schematic when BOM gets an update.
Thanks!

BARD wrote:
Thu Jul 30, 2020 5:52 am
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
It looks like there might be two full-wave rectifiers (I think) linked to the VCO.
Can you give some insight into what they’re for please?
Saw-Triangle shaping and then an octave up Triangle?
Can't understand what part of the circuit you mean. In case of snippet from original schematic - those square blocks are representing operational amplifiers used in amp/feedback part of the filter, it's just Russian notation.
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
At the bottom of the page in the middle labelled Y (or is that U?) :
http://www.ruskeys.net/pasp/alisa1387/c/alisxem3.jpg
The schematic says 32', 16' and 8', so maybe they take a triangle input and derive triangles at two and four times the input frequency.

BARD wrote:
Thu Jul 30, 2020 5:52 am
Isaiah wrote:
Thu Jul 30, 2020 2:20 am
Glad you’re looking at the 1377’s waveshaper!
Yeah, I probably will come with the board designs tomorrow. Those waveshapers are nothing esoteric, yet still sounding pretty nice. Mine would come little stripped off options, but significantly smaller than SSSR Labs SM630 AWS - such single option would benefit much from slimming ;)
Excellent! Will this PCB have mounting holes too?

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by devinw1 » Thu Jul 30, 2020 12:34 pm

Cool!

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by sirjpink » Thu Jul 30, 2020 12:55 pm

Very cool, consider me interested as well. Really nice that you would include the waveshaper too; I dig the sound of that sssr version.

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by degeneratedsines » Thu Jul 30, 2020 2:00 pm

Nice!
I remember the SSSR Labs' waveshaper to include a few specific chips like уд708 and kp159ht1

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by Zaibach » Thu Jul 30, 2020 2:21 pm

Watching this thread with interest! Also interested in the waveshaper...

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Re: Alisa 1387 filter / 1377 waveshaper project

Post by BARD » Fri Aug 07, 2020 1:50 pm

It even doesn't look bad with this blue panel 8-)
DSC_0019a.JPG
DSC_0020b.JPG
Yet it does still require some care. I'll have to adjust the ranges of pots and fix some quirks within the PCB design. I'll probably release this to you soon as PCB+Panel set. No full kits this time though :twisted:
Isaiah wrote:
Thu Jul 30, 2020 6:57 am
Out of interest, how wide (HP) will the module be?
16HP
sirjpink wrote:
Thu Jul 30, 2020 12:55 pm
Very cool, consider me interested as well. Really nice that you would include the waveshaper too; I dig the sound of that sssr version.
To be clear - the waveshaper would be another module.
degeneratedsines wrote:
Thu Jul 30, 2020 2:00 pm
Nice!
I remember the SSSR Labs' waveshaper to include a few specific chips like уд708 and kp159ht1
My designs are using standard double op-amps, as most of the sound in this case rather comes from the diodes / topology itself..

Cheers
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Re: Alisa 1387 filter / 1377 waveshaper project

Post by BARD » Sat Aug 08, 2020 3:33 am


Made some sound samples today :)

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