# Exploring Audio Signal Manipulation with Circuits

In summary: I'll get to the circuit diagram later. In summary, I'm just trying to think outside of the box and experiment.
TL;DR Summary
I wanted to get help before trying this in a circuit. Wanting to know what effect an Inductor with AC current would have on an Inductor with DC current passing through it.
I'm just playing around with circuitry, working with manipulation of Audio Signals in active circuits(My guitar, going to build an internal preamplifier). I've been trying to find an answer on this all day with no luck. As eager as I am to see what the effect would be it would be nice to know that a battery isn't going to blow up in my face or my circuit catch on fire. I'm curious about what effect an AC current passing through(back and forth) an inductor(Pickup Audio signal) would have on an inductor with DC passing through it. Two cases I wanted to try were to have them set up like a transformer, facing eachother with a magnetic core and the other, I felt it would probably have a bigger impact for the inductor with the AC to be the core of an inductor with DC passing through it supplied by a standard 9v battery with a resistor in-line.

Yes, I'm aware that the AC(Audio Signal) would be effecting the DC signal, what I have in mind is a bit more complex than using my Audio signal to effect the DC circuit. I'm just trying to think outside of the box, experiment. The bigger experiment would be some of my audio signal converted into DC but keeping the wave form, not making a constant current out of it, then manipulated by the rest of my audio signal(AC) then converted back to AC(i haven't really explored how I would do so, stuck on the topic question) then amplify in a homemade preamplifier circuit, guitar effect is the goal.

TL;DR Summary: I wanted to get help before trying this in a circuit. Wanting to know what effect an Inductor with AC current would have on an Inductor with DC current passing through it.

I'm just playing around with circuitry, working with manipulation of Audio Signals in active circuits(My guitar, going to build an internal preamplifier). I've been trying to find an answer on this all day with no luck. As eager as I am to see what the effect would be it would be nice to know that a battery isn't going to blow up in my face or my circuit catch on fire. I'm curious about what effect an AC current passing through(back and forth) an inductor(Pickup Audio signal) would have on an inductor with DC passing through it. Two cases I wanted to try were to have them set up like a transformer, facing eachother with a magnetic core and the other, I felt it would probably have a bigger impact for the inductor with the AC to be the core of an inductor with DC passing through it supplied by a standard 9v battery with a resistor in-line.

Yes, I'm aware that the AC(Audio Signal) would be effecting the DC signal, what I have in mind is a bit more complex than using my Audio signal to effect the DC circuit. I'm just trying to think outside of the box, experiment. The bigger experiment would be some of my audio signal converted into DC but keeping the wave form, not making a constant current out of it, then manipulated by the rest of my audio signal(AC) then converted back to AC(i haven't really explored how I would do so, stuck on the topic question) then amplify in a homemade preamplifier circuit, guitar effect is the goal.
I ended up just curious, in general, about what effect an inductor with AC would have on a conductor with DC. Another thing I'm curious about would be, if you were to keep a the waveform of AC in a conversion to DC, being the DC votage and current changes(if that's correct that they would both go up and down like my audio signal does, would DC in a waveform like that also be able to induce current?

Welcome to PF.

I think you need to draw a circuit diagram that shows how the coils are coupled. Attach the circuit to your next post.

A DC current through an inductor with an iron core will cause the saturation to be asymmetric, which may result in even harmonic generation.

I believe you are entering the world of magnetic amplifiers.
https://en.wikipedia.org/wiki/Magnetic_amplifier

tech99
Baluncore said:
Welcome to PF.

I think you need to draw a circuit diagram that shows how the coils are coupled. Attach the circuit to your next post.

A DC current through an inductor with an iron core will cause the saturation to be asymmetric, which may result in even harmonic generation.

I believe you are entering the world of magnetic amplifiers.
https://en.wikipedia.org/wiki/Magnetic_amplifier
Ha, as I was giving it more thought I was curious if that could be, at least, part of a process for amplification. I don't have a design for the circuit yet. I'm first trying to find ways of manipulating the audio for effects. I've read about some ways to achieve distortion with JFETs(I have 4 to 5 of them, 10 NPN's, 1 PNP, several op amps and a LM3886TF Amplifier). While I have copied many circuit examples and saved resources, like how to calculate what value of resistors and capacitors I would need based off the specs of any JFET(I have J741's) I'm still gathering information and learning about the many different ways to go about amplification. While I'm definitely going to be designing my own rather than copying one I haven't gotten to that phase yet. I'm getting ahead of myself with trying to learn ways as well as think of possible ways to manipulate audio signals for custom effects. I'm autistic and have ADD, so I'm kinda all over the place because it's all very interesting to me thus I don't have a circuit design yet.

Thank you for the link though, this is going to help a lot as for being able to explore that specific area, I wasn't even aware that magnetic amplification was a thing so odds are I may had never stumbled onto that one which will answer my questions or at least some of them. Thank you again.

Last edited by a moderator:
Baluncore said:
I believe you are entering the world of magnetic amplifiers.
Bravo @Baluncore, magnetic amplifiers are not remembered by many.

I remember because I worked with the most famous magnetic amplifier application over my head. GE had two of those signs at its Schenectady works, They had a dimming cycle, roughly 10 seconds long; one sign on while the other was off to make the sum of the power draws constant. All controlled by magnetic amplifiers. That iconic sign still pops up and people recognize it.

@Crimadella , without saturation or other nonlinearities, circuits are linear. Put two signals A and B into a linear circuit and it is the same as A+B. So you could have the same AC but with a DC offset.

@Crimadella if those inductors are not magnetically coupled then DC has no effect on nearby AC whatsoever.
It's usually the other way around , AC can have some effects on nearby conductors including inductors because of stray fields , the AC creates a changing magnetic and electric field which propagate outwards and can induce currents into nearby conductors.

A DC current can only affect your inductor if it is coupled as @Baluncore said to your circuit.
For example like having a Dc current in one of the windings of a transformer.
DC current would then build up a static magnetic field which would decrease the maximum headroom for the field in the core therefore limiting how much AC can be transferred through the core.

It's like going to a well with a bucket that is already half full with water. You now can take less water with you.

Ha, as I was giving it more thought I was curious if that could be, at least, part of a process for amplification. I don't have a design for the circuit yet. I'm first trying to find ways of manipulating the audio for effects. I've read about some ways to achieve distortion with JFETs(I have 4 to 5 of them, 10 NPN's, 1 PNP, several op amps and a LM3886TF Amplifier). While I have copied many circuit examples and saved resources, like how to calculate what value of resistors and capacitors I would need based off the specs of any JFET(I have J741's) I'm still gathering information and learning about the many different ways to go about amplification. While I'm definitely going to be designing my own rather than copying one I haven't gotten to that phase yet. I'm getting ahead of myself with trying to learn ways as well as think of possible ways to manipulate audio signals for custom effects. I'm autistic and have ADD, so I'm kinda all over the place because it's all very interesting to me thus I don't have a circuit design yet.

Thank you for the link though, this is going to help a lot as for being able to explore that specific area, I wasn't even aware that magnetic amplification was a thing so odds are I may had never stumbled onto that one which will answer my questions or at least some of them. Thank you again.
The only way you can interfere with a signal by using DC through a transformer is to decrease it's amplitude.
This is in fact how the magnetic amplifiers already mentioned here worked.
You can also pulse the DC and then decrease the amplitude of your signal only in certain parts, but either way I don't think this is what your after. I have never heard of a guitar effects circuit using a magnetic amplifier, maybe I'm just not informed but they are definitely not a mainstream thing.

artis said:
@Crimadella if those inductors are not magnetically coupled then DC has no effect on nearby AC whatsoever.
It's usually the other way around , AC can have some effects on nearby conductors including inductors because of stray fields , the AC creates a changing magnetic and electric field which propagate outwards and can induce currents into nearby conductors.

A DC current can only affect your inductor if it is coupled as @Baluncore said to your circuit.
For example like having a Dc current in one of the windings of a transformer.
DC current would then build up a static magnetic field which would decrease the maximum headroom for the field in the core therefore limiting how much AC can be transferred through the core.

It's like going to a well with a bucket that is already half full with water. You now can take less water with you.The only way you can interfere with a signal by using DC through a transformer is to decrease it's amplitude.
This is in fact how the magnetic amplifiers already mentioned here worked.
You can also pulse the DC and then decrease the amplitude of your signal only in certain parts, but either way I don't think this is what your after. I have never heard of a guitar effects circuit using a magnetic amplifier, maybe I'm just not informed but they are definitely not a mainstream thing.
When you convert AC to DC through a 4way rectifier you get a DC current, forward movement only, that is a replica of the AC wave but without a reverse flow, or -v. This is how I understand it anyway, please do correct me if that's wrong in some way. What is it that is waving in this DC signal before using capacitors to smooth the signal out to a DC constant current. Is it just Voltage that's changing, is it just current(Amps) that's changing or is it both Voltage & Current rising and falling back to zero?

To have the Inductors coupled means to have a magnetic conductor as the core which runs through both coils(each coil of the transformer). Right?

I've read a lot of, odd to me, debates about whether or not a forward bias current that is waving up and down(changing in current or Voltage or both) is viewed by some as an AC signal with a forward bias and by others as just a changing DC current just like a pulsing DC current. Why would anyone assume it's an AC signal with a 'forward bias' if it never alternates polarity, doesn't it's lack of alternating polarity mean it isn't an alternating current? Some were saying that they see it as AC because DC is a steady flow but when I looked the definition up the only thing it says is DC only flows in one direction, didn't anything about the current needing to be stable/steady.

I'm pretty sure it's safe to say that no one uses the technique I was pondering in a guitar effect circuit, at this point I doubt what I was thinking about would even work. Plus, I can't think of any way possible to be able to convert that fluctuating DC signal back to an AC signal without completely erasing the original wave structure because from what I've been looking into it doesn't seem possible. While that ends my plans to try to use that in a guitar effect I'm still curious why the fluctuating DC current wouldn't be able to induce current in another inductor. Like say for example, just making a transformer, two coils in close proximity sharing a magnetic conductive core with fluctuating DC current entering the primary coil(as it would fluctuate from a AC/DC conversion without a process to smooth the signal out). I know it would make absolutely no sense to ever do that, it would just waste power, but why wouldn't it work? Would it not create a changing magnetic and electric field to smoothly wave up and down in current and voltage? Does it have to reverse polarity, and is the reversal of polarity the main thing that causes AC to induce current into nearby coils? In both cases, as with a common core(shared magnetic conductor) and wothout.

These are my last questions on this, just out of curiosity and to gain a better understanding of this process(transformers) because it's not really looking like this is going to be useful for how I was wanting to use it. I dove into the magnetic amplifiers and that seems to work in the opposite way that I was trying think about, a DC current controlling the flow of AC.

Thanks to everyone who replied.

anorlunda said:
magnetic amplifiers are not remembered by many.
Because if you had to use them you've spent decades trying to forget. Mag amps and tape cores, ugh... Thank god for power transistors and good ferrites.

anorlunda
artis said:
The only way you can interfere with a signal by using DC through a transformer is to decrease it's amplitude.
And generate harmonic distortion due the the non-linearity of the magnetic core. As @Baluncore said before.
Mag Amps used core material with a very square B-H loop so they would act like a (really crappy) switch. But those cores are very uncommon now. Odds are he's got ferrite cores which are very non-linear when you over drive them; a more rounded off B-H loop.

When you convert AC to DC through a 4way rectifier you get a DC current, forward movement only, that is a replica of the AC wave but without a reverse flow, or -v. This is how I understand it anyway, please do correct me if that's wrong in some way. What is it that is waving in this DC signal before using capacitors to smooth the signal out to a DC constant current. Is it just Voltage that's changing, is it just current(Amps) that's changing or is it both Voltage & Current rising and falling back to zero?
You undoubtedly have a voltage source so the output of the rectifier would be just voltage PROVIDED that there isn't anything connected to it. In the real world, there's always stuff connected to it. So then, that voltage will generate current flowing through the whole circuit: source - rectifier - load. In practice, it's always voltage AND current they create each other because of the circuit they are connected to. In some (not many) circuits we approximate them as only voltage or only current because the other is too small to matter. This can get pretty advanced and subtle. But for your purposes, it's both.

To have the Inductors coupled means to have a magnetic conductor as the core which runs through both coils(each coil of the transformer). Right?
Yes, basically. You can have some coupling without a common core (an AM radio may work this way at large distances). But you will want good coupling to see the effects we are discussing, so you want a core that is well coupled to both windings.

I've read a lot of, odd to me, debates about whether or not a forward bias current that is waving up and down(changing in current or Voltage or both) is viewed by some as an AC signal with a forward bias and by others as just a changing DC current just like a pulsing DC current. Why would anyone assume it's an AC signal with a 'forward bias' if it never alternates polarity, doesn't it's lack of alternating polarity mean it isn't an alternating current? Some were saying that they see it as AC because DC is a steady flow but when I looked the definition up the only thing it says is DC only flows in one direction, didn't anything about the current needing to be stable/steady.
When you have a circuit that mixes AC and DC signals, you will see effects from both. Often we will discuss them separately, since the analysis techniques are different and in most circuits you can just add up the results at the end of the analysis (search for "superposition in linear systems" for more about this). But this doesn't work with non-linear circuits, like a rectifier, or a saturating magnetics. Sorry, no easy answer here. When people talk about AC or DC, there is an implicit assumption that they are separable or that one just isn't present. Sometimes that doesn't work.

I can't think of any way possible to be able to convert that fluctuating DC signal back to an AC signal without completely erasing the original wave structure because from what I've been looking into it doesn't seem possible.
There's nearly always a way, somehow. But, my god, it can get complicated. This sounds way above your current level of experience. In any case you would have to be precisely clear about EXACTLY what you want to do before you start. I don't really understand the details of your question here.

Frankly, you are sort of jumping into the deep end of the pool here. Which is OK for safe projects like signal processing (no hazardous voltages, currents, high temperatures, etc.). But you won't really understand it without learning some of the fundamental stuff first. Khan Academy has some really good tutorials about electronics. I would look into those since you are interested in this stuff.

berkeman
Yes, I know there has to be a circuit, or atleast a path to ground ideally with resistance so you're not just starting a fire. You answer my question on that one, still though, so thank you.

Don't worry, I'm not going to be playing with sources of real power, that's why I don't even want to try to build an Amp, plus I don't really have use for an Amp, that's where/what I'm getting my parts from. I can stick my tongue across a little 9v battery, did that plenty of times when I was a little kid so I'm not worried about that, so long as the battery doesn't explode or catch on fire. But I'll know what I'm doing, or at least knowing mostly what I'm doing and what not to do before I go to build my preamp circuit. I've already done a lot of fooling around with the passive circuitry, in my guitar, and for the preamp schematics I've already viewed a lot of them and based off of many different types of Transistors. I'll check out the link you supplied. I've been obsessively reading about this stuff for maybe two months now. I figured a changing DC current and voltage would also induce a current I was just making sure I'm right because I interpret things differently and until I registered here I didn't have a way to ask questions.

I was reading a lot about all of this about a half a year ago also, at that point, as an example, I couldn't comprehend what impedance was because of how they were trying to explain it, which now that I do know it doesn't really make sense why they would dance around it with metaphors rather than just stating that it's specifically the resistance an AC signal/current will have to pass through in a circuit, because of inductance and reactance AC and DC together in a circuit will have a different amount of resistance they encounter.

Hmmm, I don't see an edit button, I just needed to correct a tiny statement. Not, "Inductance and Reactance" but "Inductance and Capacitance", which is Reactance.

Hmmm, I don't see an edit button, I just needed to correct a tiny statement.
Below the text of your post is a line with two extra buttons.
Report - "Edit" - "Delete" + Quote - Reply
Highlight them by moving your mouse to that position.

Baluncore said:
Below the text of your post is a line with two extra buttons.
Report - "Edit" - "Delete" + Quote - Reply
Highlight them by moving your mouse to that position.
Maybe it's because I'm on a phone, or possibly because I'm new here? I don't know but, for me there is only; Report, [a lot of empty space], Quote, Reply.

Edit: Lol. Aha! I see it now. For me there is a little 'drop down' menu that isn't very noticeable and within it is the Edit & Delete button. Very odd considering there is plenty of space for Edit and Delete to not be within a drop down menu.

## 1. What is audio signal manipulation?

Audio signal manipulation is the process of altering the characteristics of an audio signal using electronic circuits. This can include changing the volume, tone, or other qualities of the sound.

## 2. How does audio signal manipulation work?

Audio signal manipulation works by using circuits to modify the electrical current of an audio signal. This can be achieved through various techniques such as filtering, amplification, and modulation.

## 3. What are some common circuits used in audio signal manipulation?

Some common circuits used in audio signal manipulation include filters, amplifiers, and mixers. Filters are used to remove or enhance specific frequencies in the audio signal, amplifiers are used to increase the strength of the signal, and mixers are used to combine multiple audio signals.

## 4. What are the benefits of exploring audio signal manipulation with circuits?

Exploring audio signal manipulation with circuits allows for a deeper understanding of how sound can be altered and manipulated. It also provides opportunities for creativity and experimentation in creating unique and interesting sounds.

## 5. Are there any potential drawbacks to using circuits for audio signal manipulation?

One potential drawback is that circuits can add noise or distortion to the audio signal if not designed or used properly. Additionally, using circuits for audio signal manipulation requires technical knowledge and expertise, which may be a barrier for some individuals.

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