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Modular Power Starvation
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Modular Power Starvation
Cat-A-Tonic
A friend of mine modded his Serge power supply to starve the entire system simultaneously. That was AWESOME!!! It sounded like an animal, really organic, amazing. love
Such a demonstration shows how the analog circuitry controls the flow of electricity organically in the same way that a woodwind or a horn controls the flow of air.
I don't think it can be done with the digital modules though.
I still haven't gotten around to making this a reality for myself; too busy building modules and enjoying the learning curve of patching.
I asked about modding a Blacet power supply a while back on the Blacet list with the same thing in mind, or building a variable power supply. Maybe people here have other ideas.

Some of the things mentioned about the topic on the Blacet list:
Is it just a simple dimmer switch as used for household lighting?
Quote:
Seems pretty simple - a potentiometer placed between the supply and
module (or power distrubutor) chokes off the voltage.

Quote:
I'm no engineer or qualified expert, but I wouldn't
crack into my PS500 --you could definitely do
unnecessary damage.
Try instead buying a pair of adjustable voltage
regulators (LM317)--one positive, one negative -- for
a couple bucks from Radio Shack and build a mini
adjustable supply for yourself. Follow the schematic
on the package, add 15v +/_ from your PS500 and you
will have an variable +/_ supply that adjusts from 1v
to 37v via 10k trim or panel pot(s). Or maybe two
trim pots (+/_)running into one master panel pot that
drops both poles at the same time. You can experiment
with dropping the power on individual modules and note
the results, and I don't think you'll hurt anything
--just don't let it get above 15v!

Quote:
The plus and minus rails must drop equally. I usually experiment with
this on mic pre-amps that use single ended, adjustable (+24v) power
supplies that are easy to adjust.

I thought you can damage op-amps in a bi-polar circuit if the plus and
minus rails do not raise and lower evenly. Correct me if wrong. Perhaps
there's protection for that in newer op-amps used.

It might be real cool to make an adjustable supply module that uses
mechanical and CV controllable potentiometers to carefully scale the
output voltage with proper protection (as a fail safe) if some component
fails.

My advice is leave your supply alone and do this circuit on a module
with it's own regulator and op-amp buffer circuit. Maybe build it with
several 'channels' just in/out and mabe dual (inverting, non-inverting)
input as previously mentioned. Then you can patch through it for the effect.

Quote:
don't think you would hurt anything by trying out a dimmer switch. You could also use a variac.

Either of those things should let you get a lower voltage, but I'm not sure if they will give you a stable low voltage, because the voltage regulators are still going to try their best to give you +/-15v DC, even if the AC input they are getting drops too low. When the input voltage goes too low they may present a sudden drop in their voltage output, followed by (I think) a sort of linear drop in output voltage as you lower the input voltage.

If you look up the spec sheets for a common voltage regulator, like the LM117 / LM317, there is probably a graph that shows possible output voltages for a given input voltage. The transformer in the power supply probably puts out around 18-20 volts AC when presented with 120V AC input, and it's output is going to drop as you lower it's input. In turn the voltage regulator will try to respond to the input voltage drop. After a certain point (depending on the regulator IC), probably around 16-17VAC input voltage, the 15vDC output voltage will start to drop or become unstable.

If you want to be able to adjust the voltage at will, and keep it stable at a voltage of your choice, you might want to get a power supply that has a 'remote sense' voltage feature. Remote sense means that the power supply has an input that you feed it's voltage output back into. This way, if the output of the power supply travels over a long cable, you can wire it back in a loop to the power supply to try and get it to compensate for the voltage drop caused by the cabling.

If you had an alternate voltage present at the voltage sense input, you should be able to use this to adjust the supply voltage from the front panel. This is just an idea and I have not tried it myself.

Power one makes power supplies with remote sense abilities. You would want to feed back a higher voltage than the input voltage if you wanted it's voltage to drop, and a lower voltage if you wanted it's voltage to rise.

Here is a link to a project for guitar pedal voltage starvation:
http://www.smallbearelec.com/Projects/SmWart/SmWart.htm
eyehue
sounds dope! but i am WAY too nervous to fuck with my power supplies on my modular.

other circuits, however, i will definitely try it out. and while again i don't know about digital "modules" getting starved, on digital oscillator circuits it definitely is effective, a lot of circuit bending uses this idea on digital stuff.

using this same concept, some people have been applying CV to the +V chip pin on some of these digital "lunetta" style circuits to great effect.

saw this mentioned on the electro-music forum:
http://electro-music.com/forum/topic-28219.html

try and share some of those serge samples, i am very curious!
eyehue
oh yea, i used to own a boss harmonist pedal, it shrieked crazy digital shit when the battery was dying. i miss that pedal.
Cat-A-Tonic
Quote:
try and share some of those serge samples, i am very curious!

I wish I had some samples of it. d'oh!
It was this guy named Anthony's Serge. He lives in SF.
3 big towers of Serge. 2 towers, each full of 6 panels of 1973 units bought from Berkley U. and 1 tower half full of new Serge.
I remember being particularly impressed with the Frequency Shifter.
That system was pimped. 8)
He controlled it from a 606 and a 303 that he claimed to have modded more than anyone else in the world. Their sizes were doubled by mods.
These were run from the same power supply so the whole rhythm got starved as well. SlayerBadger!
Roycie Roller
eyehue wrote:
oh yea, i used to own a boss harmonist pedal, it shrieked crazy digital shit when the battery was dying. i miss that pedal.


I LOVE it when the batteries in my sk-1 are dying. The loops sound like great big, clunking wheels trying to turn over.
Having a modular that's being starved would be great!
It would create a whole new world of timbre and sound from existing modules.
Kwote
Cat-A-Tonic wrote:
Quote:
try and share some of those serge samples, i am very curious!

I wish I had some samples of it. d'oh!
It was this guy named Anthony's Serge. He lives in SF.
3 big towers of Serge. 2 towers, each full of 6 panels of 1973 units bought from Berkley U. and 1 tower half full of new Serge.
I remember being particularly impressed with the Frequency Shifter.
That system was pimped. 8)
He controlled it from a 606 and a 303 that he claimed to have modded more than anyone else in the world. Their sizes were doubled by mods.
These were run from the same power supply so the whole rhythm got starved as well. SlayerBadger!


damn! so sicc!!

PS: change your avatar please. it's highly disturbing.
Cat-A-Tonic
Quote:
PS: change your avatar please. it's highly disturbing.

I thought you were literally "in to" sheep and lamb.
What's the problem with a lobster being attracted to a human female?
Besides, I gotta represent for Salvador Dali.
Where would we be without him?
...well I guess the one eyed sheep from Un Chien Andalou would probably have been happier without Dali, but look on the bright side...
You've got a Time Machine so now you can go back and skull fuck that sheep! Mr. Green


And now I return you to your regularly scheduled program:
Power Starvation!
Kwote
if you could make your avatar the whole picture it's totally cool. i had no idea what i was lookin at. it just looked fucked up for some reason. now that i know what is i'm completely aro..... woops .. uh. i'm cool. yeah it's cool.
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