Subdecay - Prometheus

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culturejam
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Post by culturejam »

Another innovative, fun, and useful pedal from the folks at Subdecay. :applause:

Here's a link if you're not familiar with this bad boy:
http://www.subdecay.com/prometheus-resonant-filter

This unit was built in 2009, and the board says "Revision 23", although I'm not sure if that is a real rev # or a joke referencing "The Illuminatus Trilogy". :hmmm:

The PCB has the circuit sections/blocks labeled on the silkscreen. :shock: I see "Env Follower", "Step Clock", "State Variable Filter", "CV mix", and "S/H" so far. I imagine this makes troubleshooting a lot easier.

All parts are through-hole (this is neither good nor bad, just an observation), 1/8-watt resistors, step clock uses a cmos 555, all op amps (14 total) are rail-to-rail, and the workhorse chip is the SSM2164 quad VCA (as expected).

I only see a trace or two on the top side (along with a shit-ton of vias and connecting traces), so either there is a ton of tracing on the bottom or it's a 4-layer board. I'll know when I have it removed from the box. More pics to follow when that happens.
Prometheus_01.jpg
Prometheus_02.jpg

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Post by Chrome Dinette »

This is one of my favorite pedals ever, certainly the best filter I have tried, though I want to get the newer version: http://www.subdecay.com/prometheus-dlx- ... ant-filter

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Post by joe_pineapple »

culturejam wrote:Another innovative, fun, and useful pedal from the folks at Subdecay. :applause:

......

I only see a trace or two on the top side (along with a shit-ton of vias and connecting traces), so either there is a ton of tracing on the bottom or it's a 4-layer board. I'll know when I have it removed from the box. More pics to follow when that happens.
great sounding pedal. looking fwd to seeing the pics (tho it already looks beyond my building ability). awesome name to 8)
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Post by Brian M »

Hi guys...

It's a 2 layer board.

The section labels (step clock, cv mix, etc) I originally put on there so I could keep track of where I wanted everything to go as I was working on it. I left them on there mostly because I thought it looked cool. It kind of reminded me a synth i worked on at one point where all the parts and boards were labeled similarly. I also thought it may aid someone in repairs some day. Probably 2/3 of the board is non-audio path so any troubleshooting could be a bit harder than a dirtbox, especially if you aren't sure what each section does.

We later switched to V2164's for the VCA, because getting them from Analog took forever. They are also a bit cheaper. We didn't notice any real difference in sound.
The filter caps in the newer ones are MLCC's

The "advanced vaporware - revision 23" is a joke, although it made a lot more sense in 2008. I had designed numerous prototypes and breadboard projects. Samples and pictures of many of them were posted on our old site going back to 2005. Basically we were accused of vaporware. It got to the point where some people were saying we would never release it. There was a proto with 12 knobs and 5 toggles at one time. Basically I tried several different ways to make a filter, and a lot of different control schemes. It took a while to really compare everything and put it in a package that didn't look ridiculously intimidating.

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Post by rocklander »

Brian M wrote:It took a while to really compare everything and put it in a package that didn't look ridiculously intimidating.
I think you've failed.. at least by the gutshots.. consider me intimidated to f^%k :lol:
great work on this thing.. it's freaking awesome.. 8)
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Post by Brian M »

rocklander wrote:
Brian M wrote:It took a while to really compare everything and put it in a package that didn't look ridiculously intimidating.
I think you've failed.. at least by the gutshots.. consider me intimidated to f^%k :lol:
great work on this thing.. it's freaking awesome.. 8)

At the time I originally did the layout for this board I was a bit intimidated my self. I did this layout with a hand-drawn schematic with eraser marks and smears everywhere. I've definitely become more organized in that regard. I at least do schematics on the computer now, so I can edit them without tearing up a piece of paper to shreds.

The stuff I've been working on more recently is a bit more complicated. The DLX version is on a 4 layer board, and not to hide anything. Even with using mostly smd IC's I needed all the room I could create. So if you think this one is intimidating...

Anyway... good luck tracing this one. I'd love to see a schematic that doesn't look like it was drawn by an angry 4th grader. :D

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Post by culturejam »

Big thanks for all the input, Brian. A class as act, as usual. :thumbsup
Brian M wrote:The DLX version is on a 4 layer board, and not to hide anything.
Of course it's not to hide anything. If there's one thing you've proven again and again, it's that you don't place any value of obfuscating what's going on in your pedals.
Brian M wrote:Anyway... good luck tracing this one.
I'm not really interested in a 100% full trace, honestly. I'm just curious how certain parts of it work. I also have your Baby Quasar, and did start a project of my own (a sloppy one) that is attempting to be an approximation. I've dropped it for now, but will be returning to it in the coming months. I'm thinking there will be an overlap or two between the Quasar family and the Prometheus family. For me, working with the quad VCAs has been not so intuitive, but I'm learning a little at a time.

Thanks again for your input. :applause:

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Post by culturejam »

I *love* the rubber "washer" on the inside of the 9v jack. Very nice way to make the connection really secure.

This thing does a really nice phaser sound as well. :shock:

Here are a few more shots, including one of the bottom side.
Prometheus_03.jpg
Prometheus_04.jpg

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Post by dlab »

@Brian M thanks for the input, I LOVE THIS PEDAL (have a black one).

@CJ, at what settings did you get that phaser sound?

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Post by culturejam »

dlab wrote:@CJ, at what settings did you get that phaser sound?
In Step mode, crank the Step pot all the way up (clockwise). Choose Triangle on the waveform switch. Turn down the Speed as desired. Adjust Depth and Intensity to taste. I like Bandpass filter mode best for this (and it's closer to all-pass phasing). :thumbsup

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Post by teej212 »

im pretty interested in the filter, is it based off anything?

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Post by culturejam »

teej212 wrote:im pretty interested in the filter, is it based off anything?
Not as far as I can tell.

Right now, pretty much nobody in the guitar effects world is doing VCA-based filters (or phasers). They aren't uncommon at all for synth applications, however.

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Post by dlab »

Thx CJ, will give it a shot today when I get home. Also I'm assuming the board hasn't changed, but will check against my Prometheus out of curiosity.

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Post by Seiche »

how does it compare to the MP SWAW? looks alot more complicated but also more versatile (sorry if this comes off as a little ignorant, i have yet to grasp the range of possiblities with this).

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Post by Brian M »

teej212 wrote:im pretty interested in the filter, is it based off anything?
The filter is essentially a state variable filter with adjustable Q you could pull out of a text book, only the dual gang pot is replaced with VCA's.

As far as the rest (control portion) it was designed from scratch, although if you break down all the basic parts of the circuit I'm sure many of you would recognize them. dual opamp triangle oscillator. 555 pulse oscillator, jfet switch for sample hold, etc etc. No real rocket science, but you'd need to be crazy enough to actually want to build it. We really should be selling tube screamers for the same price as this pedal. :D :D

It isn't really based on any other product in particular, although I'm sure there are other 2164 based filters out there, most are probably aimed at the modular synth market. One of the first projects I ever built was a parametric EQ back around 2000, which has some similarity to the state variable filter.

VCA's are not usually 9V friendly, however the 2164 is.

The power input and polarity protection is similar to something on RG's site. That is the only thing I can think of in this pedal that I didn't reference directly from either my brain or a book I own.

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Post by Brian M »

dlab wrote:Thx CJ, will give it a shot today when I get home. Also I'm assuming the board hasn't changed, but will check against my Prometheus out of curiosity.
The boards should all be the same. The only changes we ever made were the capacitor type in the filer section.... and I think we changed a resistor value in the envelope follower at one point.

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Post by pedalgrinder »

[quote][/quote][quote="culturejam"]I *love* the rubber "washer" on the inside of the 9v jack. Very nice way to make the connection really secure

You could use o-rings for vehicles thats what i use there cheap as anything you can get like 50 for $2 there millions of them out there car spare parts place will have bags and bags and bags of them. Just find the correct size for your power jack. Also stops liquids getting in. Well nothing totally stops it but helps.
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Post by pedalgrinder »

can't work out how you guys do that quote thing hmmm got me
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Post by Seiche »

pedalgrinder wrote:can't work out how you guys do that quote thing hmmm got me
you click "quote" over the post. then the quote is in a new reply and then you write over or under it. it's just code:
[ /quote]

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Post by pedalgrinder »

i'd still pretty please love a schematic on this one if it is at all possible. this is a wicked pedal [smilie=a_yumdumdoodledum.gif] [smilie=a_yumdumdoodledum.gif] [smilie=a_yumdumdoodledum.gif]
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