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SparkyCal

Mar 11, 2020
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Now that I have managed to build overdrive pedals with the 4558D op amp and with the TL082, I have gone back to my breadboard which holds the base circuit. I told myself that after I built the pedals, I'd go back and experiment with different diodes and the like, in the distortion loop.

I've done so, and have gotten some interesting effects. For example, I had a bunch of fatter looking diodes (black with silver mark for cathode), and got a lower in volume distortion effect, but it sounded fatter and tighter- which was cool.

I wonder if lasers can be set up to act as diodes in the distortion loop? After all, lasers are diodes- correct? I tried and it did not work, but I wonder whether it is because they require a voltage source?
 

VenomBallistics

Aug 30, 2018
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The actual term for the distortion loop is NFB loop ( negative feed back).
This will be on the Quiz as things evolve toward amplifiers.
You can put all kinds of stuff in the NFB loop.
Band pass filters so it processes different frequencies at different gains.
Transistors driven by input amplitude. This might give you a dynamic distortion, or a quick and dirty compressor.
Parallel distortion stages with a variety of filters and treatments so it can be more optimized for the ranges you want touched, crunched, or pulverized
It's not so much about throwing crap at it to see how it twitches, as it is sculpting things. That's where we find sophistication.
 
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SparkyCal

Mar 11, 2020
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The actual term for the distortion loop is NFB loop ( negative feed back).
This will be on the Quiz as things evolve toward amplifiers.
You can put all kinds of stuff in the NFB loop.
Band pass filters so it processes different frequencies at different gains.
Transistors driven by input amplitude. This might give you a dynamic distortion, or a quick and dirty compressor.
Parallel distortion stages with a variety of filters and treatments so it can be more optimized for the ranges you want touched, crunched, or pulverized
It's not so much about throwing crap at it to see how it twitches, as it is sculpting things. That's where we find sophistication.
@VB. I was interested in what you wrote because I was unaware of those possibilities.

I am particularly interested in two questions

1. How would I set up a parallel loop?

2. Back to the laser idea. I noticed that when I used red LEDs in the loop, they glowed red light when I hit chords hard. I thought it would be cool deploying lasers to do the same thing, except of course, it would emit the laser beam. Is there a way to do this?
 

VenomBallistics

Aug 30, 2018
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@VB. I was interested in what you wrote because I was unaware of those possibilities.

I am particularly interested in two questions

1. How would I set up a parallel loop?

2. Back to the laser idea. I noticed that when I used red LEDs in the loop, they glowed red light when I hit chords hard. I thought it would be cool deploying lasers to do the same thing, except of course, it would emit the laser beam. Is there a way to do this?
You don't actually parallel the loop, you employ multiple op amps and build each to a desired spec, and run those in parallel.
At some point you are going to discover that the stomp box creates its lead tone while stripping, or perhaps burying your rich meaty low frequencies. It may or may not annoy you and you may or may not want your low end back .. parallel stages might help you recover it similar to how the Klon Centaur mixes in a low freq bypass.

Your laser idea ......
"Hey kid ... You'll shoot your eye out"
this need not be part of a distortion pedal, and probably best that it isnt.
I'd work on building an envelope follower. All it does is monitors your signal strength, and expresses it as a DC voltage.
It should have a fairly fast attack and a moderate release, meaning, it'll swing to voltage quickly and kinda hold onto that reading just a bit.
This output signal from the envelope follower is what you'd use to trigger lasers, motors, disco balls ... raw meat catapults ...... speed dial for your attorney.
The envelope follower is a useful building block for this and much more.
It can replace a control in a pedal. Like how you saw the LED's light up when you dug into it. It works like that. But instead of making light, it might be turning up your distortion instead. or turning up your feedback in a delay to produce more echos.
Or as a sustain, where it runs your gain up as your note decays to extend it's duration.
 

Audioguru

Sep 24, 2016
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A laser can easily destroy your vision unless you limit its current and aim it away from people and reflective things.
 

bertus

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Hello,

The attached PDF shows you a lot of properties of the diodes.
Have a special look at page 7 of the PDF, wich shows some graphs.

Bertus
 

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SparkyCal

Mar 11, 2020
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Thanks everybody. I was not planning to use the laser dangerously. I was hoping to point it somewhere harmless. But I am not clear if it is even possible to use it in this circuit. Bertus; I will have a read. Thanks
 

VenomBallistics

Aug 30, 2018
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Even if you got it to work, it's stationary nature would likely fail to excite a cat anyhow.
It's belongs in a whole new set of projects.
 

SparkyCal

Mar 11, 2020
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You don't actually parallel the loop, you employ multiple op amps and build each to a desired spec, and run those in parallel.
At some point you are going to discover that the stomp box creates its lead tone while stripping, or perhaps burying your rich meaty low frequencies. It may or may not annoy you and you may or may not want your low end back .. parallel stages might help you recover it similar to how the Klon Centaur mixes in a low freq bypass.

Your laser idea ......
"Hey kid ... You'll shoot your eye out"
this need not be part of a distortion pedal, and probably best that it isnt.
I'd work on building an envelope follower. All it does is monitors your signal strength, and expresses it as a DC voltage.
It should have a fairly fast attack and a moderate release, meaning, it'll swing to voltage quickly and kinda hold onto that reading just a bit.
This output signal from the envelope follower is what you'd use to trigger lasers, motors, disco balls ... raw meat catapults ...... speed dial for your attorney.
The envelope follower is a useful building block for this and much more.
It can replace a control in a pedal. Like how you saw the LED's light up when you dug into it. It works like that. But instead of making light, it might be turning up your distortion instead. or turning up your feedback in a delay to produce more echos.
Or as a sustain, where it runs your gain up as your note decays to extend it's duration.
Assuming the present circuit, two op amps both send their out pins to the 1Uf cap , then to the 270R resistor, then to the tone pot, to the volume pot and out? Trying to envision it.
 

VenomBallistics

Aug 30, 2018
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Assuming the present circuit, two op amps both send their out pins to the 1Uf cap , then to the 270R resistor, then to the tone pot, to the volume pot and out? Trying to envision it.
we'd add an op amp to mix things down before the volume pot, and they wouldn't necessarily share the tone control either as the goal is to abuse different frequency ranges with varying levels and methods of sadism. High freqs like hot wax, while lows respond better to a good old fashioned flogging
 

SparkyCal

Mar 11, 2020
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Is this what you mean. (See attached pic)
 

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SparkyCal

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Sorry. So you mean to keeps things independent until just before the volume. Pot, correct?
 

VenomBallistics

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As I was reading the supplied material, the creator made mention of something I observed way back.
He had a preference for the use of LEDs over small signal diodes due to the higher clipping voltages.
In my own experience, different colors of LEDs also had different effects.
I imagine that these things could be leveraged to good effect in a quadrafuzz derivative.
 

bertus

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Hello,

I have enhanced the contrast of the picture:
sparky schematic 5 high contrast.jpg
You can not connect outputs of opamps together.
With some resistors in the output leads will work, or a mixing scheme like @VenomBallistics suggested.

Bertus
 

SparkyCal

Mar 11, 2020
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Actually, I am veering off this idea. What I am finding with the different op amps is that at a point, that happens fairly early, the change in sound is negligible. Especially given the nature of distortion. As a guitar player, and musically, the difference is not significant. But I love learning.
 
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