colorsound supasustain-

[highwater]

I assume that in contrast, an Optocoupler doesn't have this limitation. Would you call it a slew-rate?

An optocoupler is just an LDR and an LED in one package. You could probably find one that responds faster than the LDR you are using, but you could just as easily find a faster LDR.

In any case, I would hesitate to call it a "limitation" in this circuit - if it responded instantly, you'd need a proper envelope detector. On the other hand, then you could customise the attack and release rates.

How much of the effect is negative-feedback controlling gain on Q1 and how much is it dumping output of Q2 to ground?

I know that's probably a unanswerable question.

Not unanswerable, but it's definitely above my pay-grade.

[Hatredman]

I assume that in contrast, an Optocoupler doesn't have this limitation. Would you call it a slew-rate?

An optocoupler is just an LDR and an LED in one package.

Hummm, no...



.

[thehallofshields]

Hummm, no...

Yeah I wish they would have chosen more clear terms.
I would have preferred Optocoupler for the LDR + LED IC, and Optoisolator for Photo-Transistor + LED IC.

I found a PRR post where he said the response time of a Phototransistor was like 1μS which tells me it's somewhere in the realm of 1 Mhz

[thehallofshields]

I also get some noise from the Darlington. Sounds like a Square Wave. Frequency is loosely related to the guitar pitch. It kind of motorboats on release. Disconnect the Base, no noise.

Sounds like your Darlington might turning on/off too fast (needs filtering), and with too drastic of a transition (too much gain). This might be dumping too much current onto the ground rail. That current seems inherent to the design, though, so it might be an artifact of the breadboard and the high-ish resistances it involves. A build with a better ground connection might not have the same problem, though it's probably wise to solve it on the breadboard anyway.

I would try removing Q3, replacing it with a series diode and shunt cap(?) to create an R-C filter. Using a diode in place of the resistor will keep the compression threshold the same as using two transistors. Using a single NPN instead of a Darlington pair may reduce the gain of the LED driver and maybe not turn it on/off so hard.

The quick version of this experiment would be to just lift Q3 collector and let the base-emitter junction be your test diode.

Hopefully you don't need a filter, but a shunt cap to ground between the diode and Q4 base will help slow down transitions if you need to. I have no idea what value to use.

Thanks for all of the suggestions. Here are a few things I tried to improve the sputtering fuzz:

Circuit breaking changes:
- Generic NPN Transistor (2n3904): not enough Gain to light the LED
- Small Cap (150pF) across the LED: kills the diode from lighting
- Small Cap (150pF) from Q4c to Q4b: kills the diode from lighting

Useless ideas:
- Medium Cap (1nF) from Q4b to ground: no change
- Resistor (100kΩ) in series to Q4b: no change
- Resistor (100kΩ) from Q4b to ground: diode always partially ON, less effect

Peculiarities:
- Feed 9V from Opamp Voltage Follower: LED won't light
- Feed 9V from Battery + and - : LED won't light
- Place 2 LED's in series: LED won't light

[thehallofshields]

Anyone have an idea why the Darlington won't turn on when fed by a Opamp Voltage Follower?

I can put a LED + Resistor in that path and it lights up no problem.
This is driving me crazy.

[thehallofshields]

Hummm, no...

I'm thinking of trying the Supastain with Optocouplers instead of Trannies. Inspired by Tone God's Thunder Alley Fuzz Face.

[Phend]

Hello all:
Guess I am waking up an old post here....
I've been looking at the colorsound effects threads on DIYstompboxes, there are quite a few.
Page one of this thread has the circuit.
One question would be the voltage required, the circuit shows 9 v and some descriptions say 18 v.
My main question is this, Is the Colorsound Supasustain a good effect to build ? The LDR seems to be a challenge, in fact the circuit seems to be a challenge after reading thu the threads. Thanks in advance for any input, circuit updates.

[Phend]

Supa Voltage Requirement ?
I see conflicting voltage requirement.
Note 18 and 9
Question will this run on 9 volts ?
Thanks in advance.

[duck_arse]

I was given one of those a long time ago - never got anything out of it. it needs 18V to work properly.

[Steben]

The 220k to ground can be a 250k pot. This could give SOME controllability and could lower the LED intensity. Especially if using a bright LED.

[Steben]

Anyone have an idea why the Darlington won't turn on when fed by a Opamp Voltage Follower?

I can put a LED + Resistor in that path and it lights up no problem.
This is driving me crazy.

mm... does the (biased) opamp follower directly connect to the darlington? If both are not DC decoupled there can be issues.
When using an opamp follower, you could actually use a generic transitor instead of the darlington.

[duck_arse]

odd. a lifetime ago I was given an big black Roland AS1 and a purple Colorsound SupaSustain. the AS1 circuit is the same as the colorsound shown, but japanese transistors (but still 18V), but the board in the colorsound was a jfet-based compressor with BC transistors.

possibly the SupaSustain could be re-engineered for modern LED's, and then it might run rebiased on 9V. the original LDR in the AS1 version was a better quality metal base type. which was nfg when I got it.

[Phend]

I have a LCM6000 and BC169B's on the way in the mail from Small Bear.
Want to try to build an effect with a led/ldr.
Those parts are shown in Phil Bryant's (fuzzcentral) circuit above.
Notice the 9v supply.

[Phend]

Here is a related question to the battery supply of the ColorSound.
Question:
In the layout below is it possible the batteries might drain quickly?
(Like 18 down to 14 volts in 24 hrs)

[duck_arse]

in as much as the batteries are shown always powering the circuit - yes. as for the circuit current draw versus battery life - unknown. you would probably want to interrupt the battery ground wire via a switchy jack setup. all opinion only.