Octave down effect with tubes

[Lauri]

I was trying to find out if anyone has ever made a octave down effect using tubes, but after searching the internets for hours I didn't find anything useful. So here's a circuit I put together and it works pretty well.

Schematic:
http://www.kolumbus.fi/~kp5188/musiikki/octaver.png
First double triode is just a regular voltage amplifier and low pass filter. Second one converts the signal to square wave and the third one is a flip-flop circuit.

Sound sample:
http://www.kolumbus.fi/~kp5188/musiikki/octaver.flac

[eleventeen]

Oh yeah!! I made something like that (using tubes) when I was a kid. And a ring modulator, too. Trouble is...the sophistication and response time you can get with modern op-amps will probably devastate tube performance by any measure. Cool, though!!

[PRR]

Very clever.

[EL34]

Cool circuit!
Sounds cool too

[jojokeo]

Is this made as a stand-alone effect unit? I've did a bunch of R&D work on an old effects circuit that gives a bit of octave down called the Harmonic Percolator but it's much more subtle and actually more of a side effect of the circuit, not it's main purpose.

[tubeswell]

Awesome Lauri. Thanks for sharing.

[Lauri]

Is this made as a stand-alone effect unit?

Right now it's made on a test chassis. At some point I will either make an amp that will have it integrated in it or a stand alone unit.

[kagliostro]

Ciao Lauri

intriguing circuit 

---

Which is the value of R1 ? Is it the "standard" 1M resistor ?

Thanks

K

[Lauri]

Which is the value of R1 ? Is it the "standard" 1M resistor ?

Yes it can be 1M or whatever you want the input resistance to be.

[kagliostro]

Thanks Lauri

K

[Lauri]

Here's the schematic and a picture of a stand alone octaver unit I built.
http://www.kolumbus.fi/~kp5188/musiikki/octaversch.png
http://www.kolumbus.fi/~kp5188/musiikki/octaverpic.png

[kagliostro]

Thanks for sharing

I've a question for you

I see a pair of CF (U1A = ECC83 - U2A = ECC82) acting on a mix pot and a plate follower U2B = ECC82 as output

Why your choice was to ave a plate follower at the output instead of a CF ?

K

[Lauri]

With cathode follower as the output stage the output signal would be 180 degrees out of phase with the input signal. Which usually isn't a problem but I wanted the input and output to be in phase in case I use it in parallel with something else.

[kagliostro]

I understand, OK


Thanks for the answer


Franco

[Lauri]

Here's another flip flop circuit that seems to work quite a bit better than the one in my earlier posts.
http://www.kolumbus.fi/~kp5188/musiikki/flipflop2.png

[PRR]

> another flip flop circuit

Very ordinary.

But yes, grid-toggled is easier to slap than plate-toggled.

Tube-type is not critical. This specific plan has low-value resistors, so for a higher supply voltage you may need 12BH7 beef. But you could raise all resistances by a factor of 2 or 5 or 10 and use 12AU7. Would probably work with 12AT7 or 12AX7, real snappy.

R1 does not need to be scaled-up.

C2 C3 improve swithing time which might *not* be needed, or even best, for audio. I'd try leaving them out (save 12 cents and several solder joints).

D1 D2 could be 1N914-like small diodes; there's no need for 1 Amp parts here.