Author Topic: Boost pedal with 11 vactrols  (Read 1297 times)

somnif

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Boost pedal with 11 vactrols
« on: June 07, 2018, 03:13:07 AM »
In my ever ongoing quest to find the most absurdly overstuffed, compact, crowded PCBs in pedaldom, I happened across a gutshot of the Chase Bliss "Brothers" "Analog Gain Stage" pedal. Seems fairly straight forward, two channels of JFET/IC boost with various flavorings and colorants selectable.

Then I noticed that there were 11  vactrols siting on the PCB. What the hell? What on earth could they possibly be used for.

http://www.bestguitareffects.com/wp-content/uploads/Chase-Bliss-Audio-Brothers-Review-02.jpg

Digging around a bit more I found another of their pedals, a '3005 based delay ("Tonal Recall" https://i.redd.it/u22aycu8jwax.jpg ) , and it has 12 vactrols on it! I can understand using a couple for a bit of modulation, but 12?!? I don't get it, are they going for some convoluted opto-isolation thing (and why not use cheap photoFETs in that case)? It just seems bizarre to me.

Any thoughts on what in the world all those little photoelements might be doing?

EBK

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Re: Boost pedal with 11 vactrols
« Reply #1 on: June 07, 2018, 05:32:45 AM »
A lot of trimpots too! (Actually the first time I've seen SMT trimpots -- interesting).

Maybe all of that is to thwart copying and doesn't actually do anything. Or, perhaps an April Fool's day prank.  All the other reasons I could come up with were more absurd.  :P
« Last Edit: June 07, 2018, 05:35:02 AM by EBK »
Technical difficulties in abundance.  Please stand by.  ;-)

zombie_rock123

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Re: Boost pedal with 11 vactrols
« Reply #2 on: June 07, 2018, 05:55:38 AM »
It maybe related to the presets/dipswitches the chase bliss stuff has. Midi capable and CV options (IIRC) through to a microcontroller could warrant them to change pot values I guess

culturejam

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Re: Boost pedal with 11 vactrols
« Reply #3 on: June 07, 2018, 08:50:59 AM »
It maybe related to the presets/dipswitches the chase bliss stuff has.

It's this, I do believe. I think he uses vactrols in conjunction with switching (somehow). Dude is on a mission to get selenium into landfills in 50 years, haha.  ;D

ryanisradd

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Re: Boost pedal with 11 vactrols
« Reply #4 on: June 07, 2018, 11:30:11 AM »
The Chase Bliss pedals are the most fun/inspiring pedals I've ever played! I haven't played a Brothers but I have a Blue and Red Knob Tonal Recall and they are divine. The new Thermae is some of the coolest innovation I've seen in an analog (digitally controlled) pedal platform. (no affiliation, just a uuuuuuge fanboy) 
I make some pedals with my wife from time to time, we're called EAR electronics.

somnif

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Re: Boost pedal with 11 vactrols
« Reply #5 on: June 07, 2018, 02:10:51 PM »
Looking around that could be the case. Their Phaser has 10 of them ( http://www.modezero.com/images0000/wombtone-original-Fx.jpg ), their tremolo has 5 ( http://www.bestguitareffects.com/wp-content/uploads/Chase-Bliss-Audio-Gravitas-Review-Best-Analog-Tremolo-Pedal-04.jpg ), the flanger has 6 of them ( https://static1.squarespace.com/static/58ab033b44024386af7ae399/t/58c9fe2bebbd1a094563b461/1489632818011/ )

At least we know who is keeping silonex in business these days.

stecykmi

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Re: Boost pedal with 11 vactrols
« Reply #6 on: June 10, 2018, 10:08:01 AM »
It maybe related to the presets/dipswitches the chase bliss stuff has.

It's this, I do believe. I think he uses vactrols in conjunction with switching (somehow). Dude is on a mission to get selenium into landfills in 50 years, haha.  ;D

my guess is that he uses the DIP switches to set different bias points and uses that to control the resistance of the vactrol. basically using the vactrols as voltage-controlled resistors. pretty clever! i think this was used in early synths as a way to implement preset voices without digital controls.

culturejam

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Re: Boost pedal with 11 vactrols
« Reply #7 on: June 10, 2018, 08:52:23 PM »
my guess is that he uses the DIP switches to set different bias points and uses that to control the resistance of the vactrol. basically using the vactrols as voltage-controlled resistors. pretty clever! i think this was used in early synths as a way to implement preset voices without digital controls.

Clever for sure. But I would think the variability in min/max values in the LDRs would make it hard to get consistent results. I suppose the manufactured vactrols are tighter in that respect.