Signal Modulation Box?

[mgsrake]

Dear diyers,
I'm surfing the web for some information.
I'm looking for some circuit that can "mix" two signals, but I don't need just a mixer (summing the signals)

What I want to build it's a kind of combo-stompbox which includes 2 input (signal A - signal B) and 1 output.
Then with a selector you can chose which kind of modulation you want to apply on A and B (or either B and A).
Finally you send the modulations summed out.
the picture may help to understand the flow, actually I'm still thinknig with box model.

When I talk of modulation, I take in exam the well-known modulations for analogs signals (FM frequency,AM amplitue,PM phase, any other??).

I know that you can might ask "hey man we always use a single instrument, why did you need to modulate some others signals?"
Yes you're right, buuuuut
my idea started long time ago, when I've built a sort of "chaos box" for a frind of mine, which is just a signal (function) generator.

I wouldedd like to ear working togheter the guitar but actually haven't nothing to try i on, my question were

• "how does they sound toghter?"
• "how about modulating A over B, or B over A?"
• "what kind of modulation?"

So the question to you is:
How did i build the modulations circuits?
I can't find easy layout that I can reproduce on veroboard, did you know some source?
I'll be happy to share this idea with you once it get shaped.
thanks in advance
Luca

PS
If you think that this stuff is not feasible just argue about it, and i'll be happy to listen your reasons why.

[robthequiet]

Welcome, mgsrake.

The first thing that comes to mind would be a ring modulator.

For amplitude modulation, having an LFO applied to the gain of a signal is the basis of tremolo boxes. Applying a cutoff to the signal, as in rectification, can be used to control the rate or depth of the effect.

For frequency modulation, in analog circuits you can achieve a very modest but effective phase modulation effect, but for a wider range of effects, a good DSP system would be the best  (only) option.

Let me refer you to this other category where you might find some ideas.

[EBK]

I'm looking for some circuit that can "mix" two signals, but I don't need just a mixer (summing the signals)

Hehe. I can sense your struggle as you tried to find the words to say you needed a mixer and a mixer. 
I've sometimes found myself wishing that someone had settled that add/multiply ambiguity long ago.   

[blackieNYC]

I'm not sure I understand what you are after yet, but there are a couple things about modulation in pedals that are somewhat universal.
waveform shape, usually described as the Low Frequency Oscillator, or LFO.  Square, Sine, Triangle, Sawtooth, random.
and type of modulation.  FM and AM aren't terms we use much - you'll find more resources describing circuits that do Flanging, Phasing, Tremolo, Chorusing, and (slightly rare) Pulse Width Modulation and LFO-controlled filtering, which can be like an LFO controlling a wah-wah pedal instead of your foot.
Most of these effects listed don't really do anything when the LFO modulation is not On, unless you get creative. 

So are you saying you want to split your signal to several effects, maybe a flanger and a phaser and a tremolo, and then mix them?

What ever it is you choose, it sounds to me like you need to start with a splitter, and a mixer

if you need level controls, there is this.

[robthequiet]

The other one that comes to mind is a vocoder.

[mgsrake]

First,
Thanks to all of you for the fast answers and intrested .
I'm also very happy and excited to talk about this project with people who like to think out of the box, so many thanks.

So just for recap
In the box-model i need two circuital components that I don't actually know how to implement in this specific field.
1) the boxes that made the modulation
2) the final mixer (an esay one should just be a couple of resistors of the same resistance, correct me if I'm wrong)

The application specific frequency range is the audible spectrum (20-20KHz), so we can assume that the two signals are in this range.

Note that the modulations boxes already have the two signals as input, they don't need to generate them, eg:

• 2 instrument
• 1 instrument and voice (or voice and instrument)
• 1 instrument and a function generator (or function generator and instrument)

and so on..

so the "functions" to be modulated are already defined, and the carrier can be picked from one of them (imagine just to swap the cables, but as stated before a double deviator switch should do the trick).

Now lets try to respond XD

@robthequiet
Ouch, DSP you say? (( 
I would like to try some kind of ring modulation or others modulations, if you can help me to find some good schematic, i'll breadboard it!

@EBK
Hahahahha yeah! This word is very overloaded! Anyway I also need a "real mixer" in the final step

@blackieNYC
Thanks for your lesson, I'm really upset with the correct terminology of this field, I appreciate it.
What I need is the modulation scheme itself, because the two signals (carrier and modulating) are already given, by input.
I found very usefull the mixing step. So the mixing stage should just be parallel with resistors of same resistance right?

@robthequiet_2
Yeah it's something like that, but first I would like to try the "old simple modulations". If I remember, the vocoder mix on some specific parameter (Freq, Amp, Phase or some combination of them). This is really near to what i'll like to do with the freedom degree of chosing the modulation scheme.

[EBK]

Have you considered modulator-specific ICs?
Here's the datasheet for one Smallbear sells for $0.75 USD:
https://www.egr.msu.edu/eceshop/Parts_Inventory/datasheets/mc1496p.pdf

[robthequiet]

I'm going to suggest that we expand the range of options to include the world of synthesizers and electronic music in this universe. A simple circuit that combines (better word?) two signals so that one acts upon the other (or they act together, (words again)), is most likely going to be the ring modulator.

Just an example of a synth diy project, from the late Ray Wilson's Music from Outer Space:

Schematic, Ring Modulator Using AD633

A633 Datasheet

This may be an area to explore.

Edit: The MC1496P chip that Eric mentioned is less expensive and probably does the same thing, also worth exploring.

Cheers,

Rob

[blackieNYC]

So you are looking to modulate audio with audio content, as opposed to the idea of modulating audio with a LFO of 20Hz or less. That sounds like ring modulation to me.
Usually ring modulation (real ring modulation) will allow you to tune out the modulating signal (the "bleed-thru"), to remove it from the output, while the effect of it upon the carrier is all that remains. Like a ghost.
That chip might be a great way to do this, IF that trimpot will let you KEEP the modulation signal in the output. Otherwise there is most basic ring modulator:
http://delptronics.com/documents/RingModulatorSchematic.pdf

You can skip the 555. The diodes mix the two signals as a multiplication and not an addition. I think that's accurate to say. 
Edit - that 633 circuit looks great

[mgsrake]

Yes guys,
you've putted very intresting things on the table. 
So as stated by @blackieNYC I'll surely need the mixing stage. 

Then i'm going to try some of your ring modulation on, i'm going to check if I try some scheme on vero layout.

I'm not expert with electronics, so my wish was to find some good scheme of modulations on this field.
Anyway yes, I understand what you mean when you talk about flanging, chorusing etc...but they sound to me as a particular case of what I'm looking for: They already have a "built-in" LFO or a split of the signal itself to apply the modulation with.
My general case is to suppose that this signal is produced outside of the box, with wather you want. So again, i need to find some scheme of modulations. 
Thanks again, I keep you updated

[robthequiet]

Just one more thing to mention is that there is a chip called the FV-1 which already has a lot of programming on it out of the box. In fact, I think you can just build a circuit around it to use the default built-in effects such as echo and reverb with just switches and pots. It comes from Spinsemi.

Several forum members have launched projects with this.

[mgsrake]

Just one more thing to mention is that there is a chip called the FV-1 which already has a lot of programming on it out of the box. In fact, I think you can just build a circuit around it to use the default built-in effects such as echo and reverb with just switches and pots. It comes from Spinsemi.

Several forum members have launched projects with this.

Thanks for the hint again.
You know, i'm a software engineer but i've never putted the hands on a DSP or similar kind of programmable hardware, so i'm a little bit "scared" and I don't know really where to start with them. I think that, as in every tech field, you have to be really aware of what you're doing with it.
Despite bare hardware sometimes can be obvious, this is not the same with software...
Keep in touch,
thanks for your help

[EBK]

You know, i'm a software engineer but i've never putted the hands on a DSP or similar kind of programmable hardware, so i'm a little bit "scared" and I don't know really where to start with them. I think that, as in every tech field, you have to be really aware of what you're doing with it.
Despite bare hardware sometimes can be obvious, this is not the same with software...

Well, the nice thing about something like the FV-1 is that you can treat it like bare hardware, relying on its preloaded programming (as Rob suggested) until you are more comfortable writing your own code for it. 

Besides, the following little excerpt from the data sheet sounds friendly, right? 

For all practical purposes, the FV-1 can be treated as an analog part. Although the FV-1 is fully digital internally, it has been designed with internal power supply bypassing and careful attention to signal pin protection devices so that only a clean power supply and expected analog techniques are required at the PCB level.

[ashcat_lt]

Pretty much any effect can be adapted with a little work to have any of its parameters modulated via a control voltage.  How depends on the specifics of the circuit and what you're trying to achieve.  What it will do when the CV is an audio-rate signal also pretty much depends on everything.