LED thing idea

[livingnote]

I'm wondering about something...you know how in a guitar effect you can make LEDs act as
a clipper? How about...pointing those LEDs back at a photocell in the input stage feedback?

Or am I way off because an LED diode clipper doesn't light up enough? Just a curiosity because
if you could make something like compression dependent on distortion, then, the more distortion
you cause, the more sustain you get...maybe Don't know but just another one of those ideas...

Anybody tried something like that and then tossed it or so?

You know...like - 3 opamps or 4 afaic, one is input with gainset photocell in FB, one amplifies pretty
rotten and gets the LEDs in its FB to light causing distortion and optocompression, and then one on the output
to kinda tame the tiger again?

And, maybe just use number 4 as Vref?

 

[tv]

You would need to drive the led clippers really hot. This could be done in theory, but there must be a practical reason it hasn't been done in "known" circuits.

Basically, you are trying to "shrink" the bixonic expandora circuit (opto-comp/sustainer into rat-like clipper)

Rockman (Scholz) used a fet-based sustainer/eq into a diode clipping stage.

http://www.synthtopia.com/synth_review/Bixonic/BixonicExpandora.html


IME leds dont sound good if driven with too much current. Driving them like that may be better left for compressors, but hey, you may find some cool use for it (sound-wise). Perhaps times have changed.

Perhaps try to use two anti-parallel vactrols for clippers and dual-vactrol gain-reduction action a-la Manley.

 

[livingnote]

I was thinking as much - that if you have enough current for compression, now the distortion isn't nice anymore.

Probably in-general smartest to be able to control them separately...gonna try some LEDs in a comp sustainer
and see what happens 

There was this schemo around, like:

And I designed a layout for it using a vactrol, seeing you guys talk down there in the other thread I thought
"hey maybe two antiparallel vactrols?" Gonna try that one for sure...

 

[tv]

Probably nothing truly usable, because you are trying to:

a) defeat the purpose of a "clean" sustainer
b) because to have a good dist. sound, you need to pre-shape and post-shape eq. the circuit.

So if you try to cram all-into-one, it will be a "composite" distortion unit and not a compressor-sustainer anymore. But it is doable, I had such home-made unit in use. (fet-based gain-reduction into 1N4001/Red-LED clipper)

To retain both functions, you will need to separate the processing into two different stages (comp ---> dist) and make it switchable.

But hey, you like playing with relays...

 

[tv]

Just to defeat the "ugly number".

 

[livingnote]

Ugly number? Like, the discrepancy between what LDR likes and what clipper likes?

Yeah, relays...my power-hungry friends

There's another thing I don't understand about commercialEffectsWorld. Even though practical and handlable
for the mechanical department, 9V batteries have got to be the stupidest idea they could all come up with it
would seem. I mean, you know, not a lot of voltage, not a lot of battery life, expensive battery, the rechargeable
ones suck to high heavens...Now I have this 15V battery pack for everything consisting of 10 AA batteries, way
better.

Like: Cheaper, more bat capacity, opamp says thank you, stompbox has power forever...only drawback is "heavy".

Who would wanna trade "Heavy" for "Totally sucks and costs money"?

Is there some Estée Lauder-cosmetic "Ooooh look at how cute the little lid pops up and then that nice little
lightweight battery just fits right in, ahhaaaaaa I'm gonna put that in my purse" component I'm missing here?

I mean, surely you could add 1cm of depth to your common Boss pedal and allow for 6 AA batteries to make 9V, right?

And then make this charging wall-wart adapter with autoshutoff?

 

[tv]

No, the "ugly number" was wrt. to "post count" - my post above got the "beast" number.

But, wrt 9volts being "bad", I'm not so sure. In certain period of my life, I spent my every spare moment dicking around my home "sound-recording-system" (It didn't really deserve the "studio" name, but hey..).

This also meant producing and playing with a shitload of home-made circuits and fx (the "better" ones actually got to "live" in plastic soap-boxes, they were even more colorful than boss-pedals..) AND this also implied that I designed and made custom PSUs for the lot.

Now to the interesting part: contrary to "pro" circuits, that usually demand a full-spec voltage for the opamps, I "discovered" (well, slightly later than Jean-Michelle Jarre) that guitar circuits actually sound better when powered with 8Volt supply, i.e. slightly "starved".

The 9V battery is actually a very good power source (light-weight and one-piece), IF you design circuits with low power-demand. (LINE6, do you hear me?!)

Effect makers should get inspired by onboard guitar-pre makers in that regard.

 

[ppa]

I was thinking as much - that if you have enough current for compression, now the distortion isn't nice anymore.

Probably in-general smartest to be able to control them separately...gonna try some LEDs in a comp sustainer
and see what happens 

There was this schemo around, like:

And I designed a layout for it using a vactrol, seeing you guys talk down there in the other thread I thought
"hey maybe two antiparallel vactrols?" Gonna try that one for sure...

It's possible using one vactrol only using two opamps in balanced configuration with two diode , if you want I can post the schematic.

Pier Paolo

 

[ppa]

I was thinking as much - that if you have enough current for compression, now the distortion isn't nice anymore.

Probably in-general smartest to be able to control them separately...gonna try some LEDs in a comp sustainer
and see what happens  

There was this schemo around, like:

And I designed a layout for it using a vactrol, seeing you guys talk down there in the other thread I thought
"hey maybe two antiparallel vactrols?" Gonna try that one for sure...

however the two vactrol should have the two res in parallel if you want use two vactrols

 

[boji]

The mark of the beast is on you TV. You can not just wash it away with a fake post.

-God

 

[conleycd]

Just to come back to the topic.  I'm not a whiz or anything but what if you did this...

Instead of using the LED in the clipping circuit why not run an additional opamp buffer out of the output of the first opamp.  So... you leave the distortion circuit essentially the same (same with the LED clipper) but you drive another LED with this second opamp which is effectively isolated from the distortion circuit.  The LED would glo stronger with more signal depending on the gain structure of that second buffer opamp.  You could then use that LED for your photocell experiment in the first opamp feedback loop.

CC

 

[ppa]

this is the first schematic I've intended, that I've just designed. It's the same posted by Livignote but with the two oapmps and the two diodes circuit added, but I've in mind another more simple but less elegant.

 

[tv]

Nice one.. for a quad opamp.

Let me guess: A simpler one would look similar to this one

Or alternatively the diodes will be connected directly to the "audio-chain" opamp, and the "anti-phase" one, and the "buffered Vcc/2" will be replaced by a resistive divider?

 

[livingnote]

Basically it wasn't so much voltage I was getting at as it was the general battery format consideration...
you can totally outdo 9V blocks if you just link up some AA batteries...but what was that with 8V? Like,
does that work on cleaner effects too? I have added a nice universal power straightener-outer circuit
inside the box, and wouldn't be too hard to give it a ca. 8V Zener...

 

[tv]

8v - Theres something in a way that circuit reacts, a "response" thing.

You can do it cheaply - just insert a standard Si diode and a resistor (or a standard Si+schottky) to get the ~~1V drop. Test it for yourself, ... tamildaa. http://www.pacifier.com/~ascott/they/tamildaa.htm

Some fx I had worked better at 12V (f.e. my TC electronic phaser) ..but rare. My other pres ran @18V.

As for the format, it's way more convenient to have to pop a single piece if youre under pressure - imagine replacing n-x AA batteries in your guitars/gear when youre doing your tone check? Even the single 9volters are a MAJOR nuissance then..

But if youre aiming at recording situations, I imagine having a big-bad-totally silent and sag-less battery block having a certain advantage over the 9volters - you could make a "supersilent" PSU out of your batt-block and power several fx-boxes with it..

 

[ppa]

the other schamatic

 

[mr coffee]

There was an old circuit like you described using two vactrols back-to-back (or maybe Clairex photomods) that appeared in Polyphony or Electronic Musician decades ago where the LEDs of the optocouplers acted as signal clippers for the guitar signal.

I never heard the circuit, but it was described as having a Keith Richards kind of sound. I think the idea was mild compression and mild clipping combined. IIRC.

Don't see why the LEDs need to be green. Seems like the photocoupler LEDs were in the feedback loop of an op amp and had series resistors as well as a parallel resistor that gave linear feedback and signal amplification below threshold. I liked the general idea, but never built it.

The circuit is probably floating around the 'net somewhere.

mr coffee

 

[tv]

Hey, mr.coffee - still have your "active pickup shield" schem somewhere.

Green led would have a higher threshold compared to red.. so if used as a clipper device -and- as a photoresistor-driver at once, this combined would have a different net impact on the circuit "response".