Diodes as mixing resistors?

[Tobyk]

Since diodes only transfer current one way, will they work well as mixing resistors?

[maxkracht]

Only if you want to clip the signals you are mixing.

[Helmholtz]

Result would be half-wave rectified signal as a diode only conducts during one half-cycle of the AC signal.

[Tobyk]

Only if you want to clip the signals you are mixing.

Yes I want to split the signal for a frequency dependant clipping, and then mix that signal back again. But I’d rather not use mixing resistor that would lower gain. So basically no signal will flow through the diode the wrong way?

[Helmholtz]

A Si diode starts to conduct when its anode is around 0.5V more positive than the cathode.
For better advice please post a drawing.

[maxkracht]

This isn't the kinda clipping you are looking for. As Helmholtz says, you are rectifying the signal. Use resistors, you're not really losing gain, and making a high gain amp is all about cutting gain anyway. Could also use some other means of splitting the signal, like a phase inverter.

[TUBEDUDE]

Are you looking for a method to rout the signals to two separate chains, then recombine them after they are modified by your multi band distortion? Or are you looking for a way to split and independently distort said bandwidth?

[Tobyk]

Thanks all. I had something like this in mind, a low pass filter so that only bass frequencies gets clipped (to emulate speaker distortion). Will it work? Yes, I'm a noob..

schem.png

[Helmholtz]

With this wiring the diodes will act as a symmetrical (bidirectional) clipper (as used with many distortion units) to both the direct and the low-passed signal.

BTW, speaker bass distortion is insignificant within its rated power.

[TUBEDUDE]

You need a significant resistance between the D3 and C3.
I suspect it won't be the tone you're looking for.

[Tobyk]

You need a significant resistance between the D3 and C3.
I suspect it won't be the tone you're looking for.

But then it will be an ordinary mixing resistors circuit .
I was hoping i could use D3 instead to stop the current going backwards. Guess it’s not possible then.
About the tone, it’s possible you’re right, but I’d like to experiment some.

[Tobyk]

With this wiring the diodes will act as a symmetrical (bidirectional) clipper (as used with many distortion units) to both the direct and the low-passed signal.

BTW, speaker bass distortion is insignificant within its rated power.

Yes, but I’m trying to use D3 to stop the direct signal from going backwards, as I only want the bass frequencies clipped. Is there a way? Or is a mixing resistor the only way to do it?
I think speaker distortion (like in a small 6” speaker) is mechanical hard clipping in the lower frequencies, no?

[Helmholtz]

Yes, but I’m trying to use D3 to stop the direct signal from going backwards. Is there a way? Or is a mixing resistor the only way to do it?

Signal current is AC, so it's always running back and forth. No predominant direction.
As said, both diodes will also act on the direct signal voltage.
An additional resistor would provide at least some separation.
But the distortion content will be low.
The diode clipper will limit the distorted signal to around +/-0.6V.
Results will strongly depend on input signal level and load impedance.

I think speaker distortion (like in a small 6” speaker) is mechanical hard clipping in the lower frequencies, no?

A speaker might have something like 10% distortion at full power. But only low order harmonics, so way different from hard clipping, which produces a lot of higher harmonics and up to 48% THD.
What makes you think that speaker bass response is desirable?

[Tobyk]

Yes, but I’m trying to use D3 to stop the direct signal from going backwards. Is there a way? Or is a mixing resistor the only way to do it?

A speaker might have something like 10% distortion at full power. But only low order harmonics, so way different from hard clipping, which produces a lot of higher harmonics and up to 48% THD.
What makes you think that speaker bass response is desirable?

Ok, so is something like this is better? Asymmetric distortion for even order harmonics instead. Less low freq signal being clipped. I want to try to emulate the tone of an old cheap 6" speaker 60's Supro amp.

new2.png

[maxkracht]

Is this an amp project or a pedal project? It's rather easy to acquire cheap speakers and most of the old valco/supro amps weren't too complicated. If it's a pedal thing, you could also put a tiny speaker in a box with a microphone and get the real deal. Something like a spring reverb circuit would be a good start, just replace the tank with a speaker and a mic.