38 replies to this topic

[Antix]

Hi Seppoman,
it is the second time that I take part for a buy and I am not so experienced.
Where do I have to compile the form for SSM2164 PCB bulk order?
I have not a Paypal account but often I buy through Paypal with my card, is it the same?
Thank You for any answer
Regards

[seppoman]

so finally I managed to do a little demo using both the ssm2044 filter and the 2164 vca (with mbsid and 6581 sids).

0.00 - a sound with very high resonance, cutoff is modulated by key velocity. The filter is at the beginning of self oscillation.
0.15 - same sequence but using the vca to mute the oscillation during pauses.

0.28 - another high resonance sound with cutoff frequency tracking the played pitch, i.e. using the filter as a sine oscillator.
0.35 - same sequence using the vca.

0.46 - again a high resonance sound with cutoff as a high octave.
0.54 - same sequence using the vca, playing around with gate length and vca offset ("influence").

I guess everyone can imagine how key velocity controlling note volume sounds so I didn't record an example.

Please disregard the zipper noise present in the second and third example - I did some experiments with capacitor values last week and only remembered that after having recorded the demo and listening to the mp3 with headphones... Problem here is that the AOUT update rate on MBSID is quite low (every 2 ms), so very fast envelopes make the "ramp" of a fast attack consist of only one or a few value changes, i.e. there's huge jumps in the CV signal and the 2164 reacts with some noise. This is compensated by low pass filtering the CV a bit, in this example it's obviously not enough filtering. There's only a fine line between having these noises and filtering too much, i.e. killing the snappiness/punch of the VCA, but I'll specify a good compromise value in the final parts list.

S

Attached Files

•  2164demo.mp3   2.56MB   107 downloads

[Vytantus]

You know what I'd love to know... What parts I need to populate this board... steppoman??? BOM?

[seppoman]

The BOM is online in the WIKI now. Docu will grow over the next weeks but at least you can order parts now

[Vytantus]

yay thanks mate!

[Peake]

Thanks! This is also extremely useful in modular synths, at least one I'm working upon...the Buchla 281 quad envelopes also start as linear and expect external trimming/feedback to wrangle them into different shapes, so they're useful right there...why use a non-Buchla VCA? Because you always run out of VCAs. At least I do. And, the SSM will have more dynamic range a bit bit more attack tightness...useful as an option... And, I'm hoping that they're very useful as modulation controllers. Use the mod wheel or velocity etc. to control the amount of a DC signal such as an LFO, etc.

Brilliant!

[TK.]

This VCA is a good workaround to the SID ADSR bug... you just set the oscillators to A=0 D=0 S=15 R=0 and control volume through the SID engine's envelope.

In addition the "GSA" (Gate Stays Active) flag should be set in the OSC menu, otherwise you won't hear any sound at the release phase of the envelope

Best Regards, Thorsten.

[janvanvolt]

So do i get it right: Would it be possible, to put the SSM2164 and a AOUT_NG in a "extension box" and use the DB25 to connect it (including power !) to the MB6582 ? Or would i need modification on the PSU ?

[strophlex]

So do i get it right: Would it be possible, to put the SSM2164 and a AOUT_NG in a "extension box" and use the DB25 to connect it (including power !) to the MB6582 ? Or would i need modification on the PSU ?

Basicly, yes.
http://midibox.org/f...box-for-mb6582/

[taximan]

Hiya,
I found some well priced 2164 chips here http://www.magsmoke.com/pricelist.asp I was going to put it in the wiki but didn't want to mess it up,could someone pop it on the list please?


Prices ..............................


2164 Quad VCA Chip1 or 2, $3.50 ea;
3 to 5, $3.25 ea;
6 to 10 $3.00 ea

shipping & handling: US / Canada up to 10, $2.50

EU/UK/Aus up to 10, $4.50
shipping & handling $1.50 if ordered with PCB






cheers
Paul

[grizz]

Oh man do I have a dumb question that I can't figure out the answer to myself...

Is the ssm2164 module bipolar or unipolar?

I am leaning towards unipolar since I can get it to work i unipolar and not in bipolar.



Cheers,

grizz

[Shuriken]

Oh man do I have a dumb question that I can't figure out the answer to myself...

Is the ssm2164 module bipolar or unipolar?

I am leaning towards unipolar since I can get it to work i unipolar and not in bipolar.



Cheers,

grizz

Well, the J5 connector on the PCB says +, GND and -. So i would say bipolar.

[grizz]

That makes sense. The +grnd- is why i initially tried to set it up in bipolar mode. I must have done something wrong while trying to calibrate it with my AOUT_NG in bipolar.

Thanks,
grizz

[seppoman]

Uhm, I see I should really get started with doing more docu...

as a general rule of thumb you can assume that everything that doesn't specifically mention a bipolar control voltage will expect an unipolar CV. In the case of this module, IIRC the dynamic range of the regular CV range (0 .. 11.67V) is about 65 dB, with 0V being "silence" and 11.67V being unity gain. I have never thought about what happens if you apply a negative voltage to the CV input...

Regarding your "+ GND -" reasoning - Although the docu doesn't exist yet, one might assume, also by comparison to the 2044 module, that this module will not be powered by love and fresh air So J5 is obviously the only connector where you could come to the conclusion that it might have something to do with power supply. Just like the AOUT(NG), the 2044 board, the MB_FM module etc, it expects a bipolar power supply of +/- 12 V and GND.

Note also that generally a bipolar control voltage (CV) still doesn't mean that there are more than two wires involved, just the one signal can be above or below GND.

S

[xerox]

do you share also a pcb layout and scheme ?

thanks

[wicked1]

I'm wondering the same thing.. Anyone have a schematic for this?

I found one that is quite similar, and I think I've mostly reverse engineered this one by looking at the parts list and photos. The cv inputs have me a little confused. Basically there's a 27k resistor, and I don't know where it goes. Looks like the cv goes in to a 27k resistor that is immediately connected to a 2nd 27k resistor at the input of the 074. I can't tell if anything else is going on at that junction (I'd guess so, else why would there be 2 27k resistors in a row, instead of one larger) I think that's the input filter to smooth cv, but I still don't quite get it, as I don't think the cap there goes to ground like a standard lowpass..... Maybe I need to sketch what I think is going on and have someone look at the schematic.

[wicked1]

Ok, here's a quick schematic of what I think is going on.
I didn't add the 2 electro and 6 smaller power supply bypass caps to my schematic, but those are obvious.

There's the extra 27k res at the input that I need help figuring out.
Also caps 21-24 are next to the VCA chip on the board photos and not on the parts list. Can someone who has built this, or knows what they are doing let me know if this looks right, and let me know where the missing 2 parts go?

I'm guessing the 4 caps at the 2164 are bypassing the cv input to ground.. Not sure on the resistors at the input yet. It looks like they're connected to a trace that goes somewhere and not the ground plane.

Thanks!

Attached Files

•  vca2164.jpg   37.9K   50 downloads

Edited by wicked1, 30 April 2012 - 01:47.

[wicked1]

I'm about to breadboard this VCA, but was thinking...... to the people who have built it, do you really get much use out of it? I built the ssm filters, but don't think I'll have them up to self oscillating very often. Then, since you can only automatically route the volume to it, it must take a bit of effort to re-do your patches and map the EG to the external VCA.
So, is it worth the effort?

Thanks!

[NorthernLightX]

Small bump: I'm getting into modular stuff, partly because this allows me to finish stuff and expand on it later (opposed to the earlier mantra of "let's spend hours upon hours searchin for extra stuff I can add and never get this thing finished").

I've come to the conclusion that I want to make all my Midibox (SID) CV output's bipolar, but this would make them incompatible with this VCA, which expects a CV range of 0-10V.

I have recently aquired one of these VCA boards and want to make a companion board for this to make it compatible with a CV voltage of +/-5V. A simple solution would be to introduce a simple CV level shifter, that would add 5V to the +/-5V, making it 0-10V. I want to add a CV attenuator as well. The necessary components would involve 4 dual opamps (probably TL072) with 2 100n decoupling capacitors each, 2 small electrolytics for power integrity, a couple of resistors, 4 trimmers, and 4 potentiometers.

Is there any public interest for such a companion board? If so, I'll make a design topic for it and offer a small bulk order for the final PCB in the end. If not I'll just dump the components on some veroboard and be done with it