Hello, most probably a beginners error, but here it goes.

I've just got an Erica BQVCA and to my surprise it bleeds, it is never fully closed. Is this a common feature of this module? VCA's that bleed its such a bummer, and FOUR!!?? I have an Erica powered skiff case, so it shouldn't be an issue of cheap power source.
I also got a Black Dual EG/LFO, didn't like it either, it just doesn't go slow enough, very limited in this respect, pretty dissapointing, think I should've spent the money on a MATHS... Anyway, has anyone tried or has a QUAD VCA? Is there a way to fix this bleed? Should I contact Erica Synths?

Many thanks!

Cheers!


Hi Pricto,

Not sure if it's normal for the Erica Synths - Black Quad VCA to bleed, perhaps indeed the best is to check this out with Erica Synths. I don't have this particular module, so I can't test it for you. I have quite a few other Erica Synths modules but haven't notice any bleeding.

I do have a Black VCA though, so I just tested it to be sure but it doesn't bleed. So yes, perhaps better check with Erica Synths.

On the other hand, I have the Doepfer A-138p mixer and that one does bleed a little bit. If it's totally quiet in the room and I haven't opened the volume (completely at zero) of the channels then I still can hear them very far away. At the moment of writing, if I carefully listen, I can hear some sound now (the bleeding from the A-138p). I also just all switched the mute switches to mute but still can hear it a bit (the A-138p I am talking about here). But I don't have that with the Black VCA.

Not sure if this helps, better check with Erica Synths and please do let us know. Good luck and kind regards, Garfield Modular.


Hi GarfieldModular,

In my Black Quad VCA the bleed it's also dim, and just found out that it becomes louder if the pre-amplification from the mixing board is high (of course), if the pre-amp is low it's practically inaudible. Maybe it is because I'm going straight from the VCA output to the mixer. I also have a Black Dual VCF, and if I patch the oscillator into the VCF and then to the VCA and turn the in level from the VCF all the way down, it shuts the sound completely (as expected). Leaking only appears on the VCA at high pre-amping from the mixer but not from the level control of the filter.

Another curious thing I've noticed is that when I turn up any knob from the Quad VCA, signal starts to appear (at low level pre-amplification on the mixer) at about 11 o'clock, before that point is completely silent. From then on the sound comes up smoothly and gradually, and starts to reach amplitude in what seems a rather exponential fashion. Don't know if this is normal either (maybe I'm just being too picky, I'm a sound technician).

Thanks for the reply, I'll try to contact Erica.

Cheers,

Pricto.


Hi Pricto,

Ah yes... if you don't use an Audio interface with output to your external mixer then your output signal is "too hot". Eurorack signals have a higher audio voltage than the usual audio lines, so that might be one reason. Try to use an audio output interface module to provide a good signal level to your external mixer.

I know there are lots of members here who do this directly without an audio interface module, like you do at the moment but since you are a sound technician, I do think you should do it the proper way :-) I.e. with an audio interface module. But up to you of course.

Your description of the Black Quad VCA that the signal starts to appear only at about 11 o'clock onwards, that's what I roughly recognise and experience with my Black VCA too, so perhaps that's just Erica Synths?

I don't think you are too picky, checking on certain things and make sure that everything is all right, is in my opinion, not being picky.

Let me know what Erica Synths tells you about that Black Quad VCA and good luck. Kind regards, Garfield.


+1 on Garfield's comments here. People shouldn't be trying to feed synth-level signals to outboard devices. OF COURSE it'll sound like it's leaking...because you're taking about signals that can swing up to +/- 10V, and feeding these into something that either wants to see 1.4 or .775V. Since you're an audio tech, I shouldn't have to explain why this doesn't work, and also why an isolated, balanced output will improve matters as well.


Ok, It's what I thought. I suppose it's an impedance issue. The thing is that if it sounds, even pre-amplified, it should be leaking, at least at a very low amplitude, maybe not noticeable when the output signal level is attenuated. I made the comment because I've read that some Buchla VCA's in the seventies leaked and it was part of their charm, I thought that maybe Erica went for something similar. The thing that I would like to know is if all VCA's leak at a very low level, or are there completely silent devices, so as if I connect a very compressed distortion at the end of the VCA it wouldn't pull up the leaking. Anyway, I'm waiting for a Befaco line output module, hope it stops the leaking completely.

Many thanks,

Cheers!


Hi Pricto,

You are welcome and please let us know once you received the Befaco - Out v3 if you still have any leaking issues, and if yes, how serious they are.

Good luck and kind regards, Garfield.


Some VCAs do leak. But most decent-quality modern ones (like what Erica uses) don't...at least, not without a reason. Another thing worth checking is whether there's an accidental low-level offset voltage getting into the control side, as this will definitely cause audio leakage from the VCAs not being able to fully close down. It doesn't take MUCH...just a tiny fraction of a volt.

Another possibility could be voltage from an outside source. Case in point: many years back, I was working with our local community radio station in several capacities. One of these was maintenance. One evening after close-down, I and another engineer were trying to figure out why the station's Harrison AIR7 would suddenly switch channels off or on without warning. It was definitely a primo radio console in its day (hell, I've used Harrison desks as far back as my first year of undergrad), so the behavior was downright weird. But it's also worth noting that, when it was installed, they also put in the remote-start lines...but then never connected them to the turntables, cart decks, etc. So they were just hanging there...cables to nowhere, only a few feet long.

At the same time, we also had an FM station dead-smack in the center of town, pumping out 10 kW. I knew already that it had an annoying tendency to creep into audio lines both at our station and at other broadcast facilities in the area. So, how could that be an issue here?

Well, it so happened that, after a bit of antenna length calculation on my part, the disconnected remote-start lines...which, of course, also connected to each channel's ON/OFF logic...were cut so that they were all around a quarter-wave's length at 92.5 MHz, which was the other station's operating frequency. After I cut all of those (as they weren't in use anyway), the "ghost" of the AIR7 was successfully exorcised.

So what the hell was going on? Simple. There was enough induced voltage on each wire that it would send voltage back to the board's ON/OFF logic for each strip. And when there was a particularly loud signal on the one station, it would "hi-state" the strip's logic...which in this case, was being interpreted as an OFF signal.

So you might check around for sources of RF in addition to the typical synth bugaboos. After all, it doesn't take very much voltage to open a VCA a tiny bit...even less than I had to chase down in the story above.


I've been using the device always in the same room and area, I'll try other spots of my apartment and outside to discard the possibility of a specific RF creeping somehow in the device and keeping the VCA's slightly open. Still waiting for the Befaco - Out v3 module, will inform of what happens.

Thank you very much for the advice!

Cheers,
Pricto


Hi guys, received the Befaco - Out v3 and still leaks as I predicted. I've tried in other places in my apartment and the same. Also when I use the Black Dual EG/LFO, the VCA never closes completely after a CV opening and closing of the VCA, when I pull the volume up of the VCA when it is supposed to be closed by the EG, I get almost a full signal out of the VCA... Don't know if the EG is not working properly either. Will send video to Erica Synths to see if it's working properly or not.

Cheers,
Pricto


Hi Pricto,

Sounds to me that the module might have an issue. Let's see what Erica Synths says. You might need to send the module to them for repair or check; but up to Erica Synths of course to analyse this accurately.

Good luck and kind regards, Garfield.


Hello, I've just got an answer from Erica Synths and they say it is normal for this VCA to leak a little bit.
Guess I'll have to get myself something different, thanks for everything.

Cheers,

Pricto.


Hello Pricto,

Thank you very much for your feedback and I am sorry for you that your VCA doesn't meet your expectations :-( Good luck with the search for a VCA without bleeding. It would be nice to know once you have found "your VCA", which one that would be :-)

Kind regards, Garfield.