Stuff you wanted to know but were afraid to ask

Very do-able.

In the case where you might need a 3-terminal (TRS) interface, you could connect the Vactrol's LDR between Tip & Sleeve and connect a fixed resistor, something in the neighborhood of 10K to 100K, between Tip & Ring.
 
I thought they were TRS(the 2 "hot" or tip wires)was because only 1 cable/jack is involved and how would you send the signal back?
 
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Ok here's a big learning moment for me and a duh! moment for you.

I know the value of volume pots in guitars affects how bright they are. The more resistance they have, the less high end bleeds to ground and the brighter the guitar is.
So I suppose this applies to pedals as well.

If I want to make a pedal brighter, should I use a larger volume pot? And vice versa.

So a Fuzz Face has a lot of bass and it uses a 470/500k volume pot to retain high end. Makes sense.

Why does Analogman reduce the bass by using a 1uF input cap only to darken the pedal by using a 250k volume pot?
Doesn't that essentially make the pedal mid-heavy?
 
that's what I thought... constant voltage out, pedal replaces normally seen knob on the rheostat/potentiometer, return voltage determines volume. other than the rotating foot pedal, should be amongst the easiest to build, IE got a housing rest is brain donor hard.
 
Here's the low-down on volume controls:
On guitars, Volume controls interact with the pickups, the cable and the next device in the chain.
Pickups have a DC resistance, that's the number we see quoted in advertisements. "Our hot humbuckers are wound to 12K." Pickups also have an AC impedance and that varies with frequency. All magnetic pickups have an electrical resonance, usually in the 3KHz to 8KHz range. At resonance, the pickup signal is strongest, and the pickup's output impedance is also at its highest. Any loading of the pickup, whether it's from the Volume control, Tone control, cable, or the stuff on your pedal board, will affect the pickup's frequency response, especially at resonance. It's the resonant peak that is responsible for a large part of a pickup's brightness. Higher value Volume controls provide a lighter load to the pickups and let more of the "sparkle" come thru.
When we turn the Volume control down, we're putting some resistance between the pickups and the cable, and everything downstream of the cable. The Volume control's resistance and the cable capacitance form a low-pass filter which darkens the tone. This is reason for installing a Treble Bleed on a guitar's Volume control. The Treble Bleed helps compensate for the high freq loss in the cable. It's not perfect, but it helps.
When we introduce resistance between the pickups and the first (active) pedal in the chain, we can affect that pedal's behavior. The Fuzz Face is a prime example. It has a very low, non-linear input impedance. It loads the pickups, reducing the treble and creating distortion right at the input of the pedal. When a pedal advertisement touts "responsive to guitar volume," that's one of the reasons why.

In summary, larger value guitar Volume controls can result in a brighter tone and stronger interaction with pedals.

OK, so much for guitar Volume controls, What about pedal volume controls?
Most pedals have their Volume control at the very end of the circuit. Notable exceptions are any pedal with buffered bypass. Pedals generally have a much lower output impedance than pickups. They are less susceptible to loading from the pedal's Volume control. But, the pedal's Volume control will form a low-pass filter with the capacitance of any cable that comes after it. A larger value Volume control will have a lower cutoff freq. The filtering effect is strongest when the volume control is at the electrical midpoint. That's noon with a B-taper pot, but more like 2:30 with an A-taper pot. At 7:00 and 5:00, the volume control's resistance is zero and then it's not part of a low-pass filter. The original Fuzz Faces did not have tone controls or any filtering at the end. Pedal builders installed large value (500K) Volume controls so that they'd get some filtering from the Volume control and the cable capacitance.

Larger value pedal Volume controls result in a darker tone IF the pedal's Volume control is at the very end of the circuit. The pedal's Volume control can also interact with the next pedal in the chain, much like a guitar's volume control.

Lotta words, I know. Hopefully it makes sense.
 
Chuck D. Bones said:
Here's the low-down on volume controls:
On guitars, Volume controls interact with the pickups, the cable and the next device in the chain.
Pickups have a DC resistance, that's the number we see quoted in advertisements. "Our hot humbuckers are wound to 12K." Pickups also have an AC impedance and that varies with frequency. All magnetic pickups have an electrical resonance, usually in the 3KHz to 8KHz range. At resonance, the pickup signal is strongest, and the pickup's output impedance is also at its highest. Any loading of the pickup, whether it's from the Volume control, Tone control, cable, or the stuff on your pedal board, will affect the pickup's frequency response, especially at resonance. It's the resonant peak that is responsible for a large part of a pickup's brightness. Higher value Volume controls provide a lighter load to the pickups and let more of the "sparkle" come thru.
When we turn the Volume control down, we're putting some resistance between the pickups and the cable, and everything downstream of the cable. The Volume control's resistance and the cable capacitance form a low-pass filter which darkens the tone. This is reason for installing a Treble Bleed on a guitar's Volume control. The Treble Bleed helps compensate for the high freq loss in the cable. It's not perfect, but it helps.
When we introduce resistance between the pickups and the first (active) pedal in the chain, we can affect that pedal's behavior. The Fuzz Face is a prime example. It has a very low, non-linear input impedance. It loads the pickups, reducing the treble and creating distortion right at the input of the pedal. When a pedal advertisement touts "responsive to guitar volume," that's one of the reasons why.

In summary, larger value guitar Volume controls can result in a brighter tone and stronger interaction with pedals.

OK, so much for guitar Volume controls, What about pedal volume controls?
Most pedals have their Volume control at the very end of the circuit. Notable exceptions are any pedal with buffered bypass. Pedals generally have a much lower output impedance than pickups. They are less susceptible to loading from the pedal's Volume control. But, the pedal's Volume control will form a low-pass filter with the capacitance of any cable that comes after it. A larger value Volume control will have a lower cutoff freq. The filtering effect is strongest when the volume control is at the electrical midpoint. That's noon with a B-taper pot, but more like 2:30 with an A-taper pot. At 7:00 and 5:00, the volume control's resistance is zero and then it's not part of a low-pass filter. The original Fuzz Faces did not have tone controls or any filtering at the end. Pedal builders installed large value (500K) Volume controls so that they'd get some filtering from the Volume control and the cable capacitance.

Larger value pedal Volume controls result in a darker tone IF the pedal's Volume control is at the very end of the circuit. The pedal's Volume control can also interact with the next pedal in the chain, much like a guitar's volume control.

Lotta words, I know. Hopefully it makes sense.
Click to expand...
Thank you Chuck!

Most of it went whoosh over my head but basically volume pot resistance works opposite in pedals, more resistance means a darker pedal right?

Time to test that on a breadboard to see it in action. Let's see if I can darken a Fuzzrite and brighten a Fuzz Face.
 
Here’s another one that I only just thought ab whilst messing with my Sonic Reducer pedal that leaks a high pitched whine even when in bypass. Why does the common footswitch wiring ground the input of the circuit when in bypass, when conceivably those pedals that may exhibit clock/lfo noise or digital whine when in bypass might benefit (presumably) from grounding the circuit out when in bypass. I guess to answer part of my own question, sometimes the noise is passed from those chips by virtue of proximity to the wiring/insulation.
 
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There are a few reasons for grounding the input to a pedal circuit when in bypass mode.
1. High-gain circuits can pick up and amplify radio interference when their inputs are left floating. That amplified noise can then bleed into the bypass signal.
2. High-gain circuits can oscillate when their inputs are left floating. The oscillation can then bleed into the bypass signal.
3. Grounding the input ensures that the input side of the input coupling cap has zero volts on it in bypass mode, which prevents popping when the stomp switch is toggled. An anti-pop resistor serves the same purpose.

Everything inside the pedal is coupled to some degree due to proximity and shared power and ground. We do what we can to minimize stray coupling by carefully routing the traces and wires, using a ground plane on the PCB, grounding the enclosure and pot bodies, etc.
 
Diynot said:
Here’s another one that I only just thought ab whilst messing with my Sonic Reducer pedal that leaks a high pitched whine even when in bypass. Why does the common footswitch wiring ground the input of the circuit when in bypass, when conceivably those pedals that may exhibit clock/lfo noise or digital whine when in bypass might benefit (presumably) from grounding the circuit out when in bypass. I guess to answer part of my own question, sometimes the noise is passed from those chips by virtue of proximity to the wiring/insulation.
Click to expand...
I was going to ask if the Input goes to Ground in Bypass to stop Bleed from the Circuit on your build.
It's a well known mod to do to older style pedals & standard practice nowadays!

Chuck answered it for you!
 
Chuck D. Bones said:
Here's the low-down on volume controls:
On guitars, Volume controls interact with the pickups, the cable and the next device in the chain.
Pickups have a DC resistance, that's the number we see quoted in advertisements. "Our hot humbuckers are wound to 12K." Pickups also have an AC impedance and that varies with frequency. All magnetic pickups have an electrical resonance, usually in the 3KHz to 8KHz range. At resonance, the pickup signal is strongest, and the pickup's output impedance is also at its highest. Any loading of the pickup, whether it's from the Volume control, Tone control, cable, or the stuff on your pedal board, will affect the pickup's frequency response, especially at resonance. It's the resonant peak that is responsible for a large part of a pickup's brightness. Higher value Volume controls provide a lighter load to the pickups and let more of the "sparkle" come thru.
When we turn the Volume control down, we're putting some resistance between the pickups and the cable, and everything downstream of the cable. The Volume control's resistance and the cable capacitance form a low-pass filter which darkens the tone. This is reason for installing a Treble Bleed on a guitar's Volume control. The Treble Bleed helps compensate for the high freq loss in the cable. It's not perfect, but it helps.
When we introduce resistance between the pickups and the first (active) pedal in the chain, we can affect that pedal's behavior. The Fuzz Face is a prime example. It has a very low, non-linear input impedance. It loads the pickups, reducing the treble and creating distortion right at the input of the pedal. When a pedal advertisement touts "responsive to guitar volume," that's one of the reasons why.

In summary, larger value guitar Volume controls can result in a brighter tone and stronger interaction with pedals.

OK, so much for guitar Volume controls, What about pedal volume controls?
Most pedals have their Volume control at the very end of the circuit. Notable exceptions are any pedal with buffered bypass. Pedals generally have a much lower output impedance than pickups. They are less susceptible to loading from the pedal's Volume control. But, the pedal's Volume control will form a low-pass filter with the capacitance of any cable that comes after it. A larger value Volume control will have a lower cutoff freq. The filtering effect is strongest when the volume control is at the electrical midpoint. That's noon with a B-taper pot, but more like 2:30 with an A-taper pot. At 7:00 and 5:00, the volume control's resistance is zero and then it's not part of a low-pass filter. The original Fuzz Faces did not have tone controls or any filtering at the end. Pedal builders installed large value (500K) Volume controls so that they'd get some filtering from the Volume control and the cable capacitance.

Larger value pedal Volume controls result in a darker tone IF the pedal's Volume control is at the very end of the circuit. The pedal's Volume control can also interact with the next pedal in the chain, much like a guitar's volume control.

Lotta words, I know. Hopefully it makes sense.
Click to expand...
I still don't quite understand phrases "it loads the pickups down" or "(thing) loads (previous thing in chain)". What does that mean, exactly?
 
mhshizz said:
I still don't quite understand phrases "it loads the pickups down" or "(thing) loads (previous thing in chain)". What does that mean, exactly?
Click to expand...
That’s pretty technical. Loading refers to how much current the next stage absorbs. Or to be more precise, how low the input impedance is. For guitar pickups you usually want the first stage to absorb as little current as possible otherwise the sound gets dark. Intuitively you can imagine that a passive pickup cannot provide a lot of current to the next stage because it is, well, passive. The technical explanation is more complicated and has to do with impedance mismatch and the frequency domain but I find that the intuitive one is pretty decent.
 
Indie rock was what happened when you couldn't stand Def Lepers or Bon Jovi and wanted to listen to the Pixies instead. It was kinda like punk again except with weirder music. But of course the label is, indeed, meaningless these days. "Indie" comes from independent, as in "not on a major label". Again, meaningless these days. Just as "punk" no longer has any meaning. What passes for punk these days is nothing like the original. It has become its own corporate genre and I'm not sure how modern punk is any different from modern anything else!

Indie is the term people use these days when they used to say alternative. But the genre thing is pretty meaningless. It's a kind of lazy shortcut to indicate which kind of noise we like. It's not great but what else do we have?
 
giovanni said:
That’s pretty technical. Loading refers to how much current the next stage absorbs. Or to be more precise, how low the input impedance is. For guitar pickups you usually want the first stage to absorb as little current as possible otherwise the sound gets dark. Intuitively you can imagine that a passive pickup cannot provide a lot of current to the next stage because it is, well, passive. The technical explanation is more complicated and has to do with impedance mismatch and the frequency domain but I find that the intuitive one is pretty decent.
Click to expand...
So when something is "loaded down" it's not being allowed to pass along as much current as it otherwise could?
 
mhshizz said:
So when something is "loaded down" it's not being allowed to pass along as much current as it otherwise could?
Click to expand...
I think it means we are trying to absorb too much current from it, affecting high frequencies (the energy we are trying to absorb is not there and comes off the high frequencies first).
 
mhshizz said:
So when something is "loaded down" it's not being allowed to pass along as much current as it otherwise could?
Click to expand...

What's all this Impedance Stuff About?

I'll keep the math to a bare minimum, but you can't describe impedance without a little math. When I was in college, the professor in an introductory course on circuit theory shared this anecdote: "As part of their oral exam, PhD electrical engineering students were asked to define the term...
forum.pedalpcb.com forum.pedalpcb.com
 
giovanni said:
I think it means we are trying to absorb too much current from it, affecting high frequencies (the energy we are trying to absorb is not there and comes off the high frequencies first).
Click to expand...

benny_profane said:

What's all this Impedance Stuff About?

I'll keep the math to a bare minimum, but you can't describe impedance without a little math. When I was in college, the professor in an introductory course on circuit theory shared this anecdote: "As part of their oral exam, PhD electrical engineering students were asked to define the term...
forum.pedalpcb.com forum.pedalpcb.com
Click to expand...

spi said:
I found this post helpful in understanding buffering and loading:
Buffers, impedance and other internet lore – Mr. Black (mrblackpedals.com)
Click to expand...

I truly appreciate all your efforts. Chuck's post seems to be above my head technically, while Mr Black's article features a painfully juvenile writing style and analogies I can't quite parse.

It seems this is a "me" problem, so I'll just go back to telling myself to not worry about and trust that people I respect behind the projects I like know what they're doing.
 
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