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Blacet Quad VCA
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author Blacet Quad VCA
i was just lookin it over on the blacet page:

and i noticed on the bottom it say this:

* Requires resistor changes

call me a moron(go ahead. do it!) but what would this entail?
de solder and remove 4 resistors and replace with a different value

then break 4 tracks on the pcb and soldering in 4 new resistors

this is from memory so I could be wrong it was over a year ago that I converted 1 for my MOTM format system

cheers Paul D

ok, its a mod that you dont need if you are only using a frac modular.
thats about it!

the mod is for us morons who think we can just mix and match 5v CV modulars with 10v CV modulars.

actually, you might want the mod if you were using motm envelopes in your frac rack.

PS: why did i think the QUAD vca was discontinued?
The manual for it has details about it near the bottom:

The normal control voltage range of the VCAs is 0-10V. This can be changed to 0-5V by doing the following:
- Change RA (R17, 18, 19, 20) to 66.5K (four places).
- Cut the RB traces (solder side of PCB) and install four 100K 1% resistors (standing up).
- Change R11 to 49.9K
- Change R7 to 82K.
- Adjust RT1 for 5.0V (See “Calibration”.)

Channel D has 10X gain. To make this 1X, replace R8 with a 100K 5% resistor.
consumed wrote:


consumed wrote:
the mod is for us morons who think we can just mix and match 5v CV modulars with 10v CV modulars.

i see. that would explain the 5v option on the blacet order page.

but yeah i don't think i'll be doing any mixing and matching. someday i plan on moving into the Wiard 300 system. but that's a whole other kettle of wogglebugs.

consumed wrote:
why did i think the QUAD vca was discontinued?

it's on it's last run as far as i know. once they're gone, they're gone.
Muff Wiggler
yeah, they were discontinued at the same time as the Dual Manual Filter, Final Filtre and Frequency Divider. Mid summer 2006 was the announcemt, I believe.

At the time John said "once the current stock is out, they are done". At the time he also told me he had enough QuadMix VCA stock to last 'over a year'. So there's still probably a few left.

The default configuration for it expects 0-10v to fully open the VCAs. This is also true of the other Blacet VCA (Dual Lin). The Blacet EG1 creates 10v peak envelopes (but it has an attenuator knob so you can scale that down if you are firing a VCA that expects less voltage).

As has been often discussed, MOTM envelope generators peak at 5v, and MOTM VCA's expect only 5v to be 'fully open'. You can fire a MOTM VCA from a Blacet EG1, you just need to attenuate the output of the EG1 down to 5v by using the knob.

However, MOTM envelope generators only create a 5v peak. If you try to fire a Blacet VCA with one, you will only get the VCA 'half open' in the default Blacet configuration.

The 'resistor change' option for the Blacet VCA changes the behaviour so that the module fully opens up with only 5v applied - perfect for using the VCA with MOTM envelope generators.

You can also order the VCA assembled from Blacet in a 5v configuration. It's on their order page.
Does someone remember the price of quad vca new please ?
Muff Wiggler
$186 assembled, $130 kit.
i have a quad vca kit and i populated the pcb. i never got around to building it. pm me if interested.
I'll be selling 2 of them, modded for 5V, in the near future.
Thanks Muff
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