Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Lauri on August 05, 2014, 10:24:37 am
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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 (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 (http://www.kolumbus.fi/~kp5188/musiikki/octaver.flac)
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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!!
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Very clever.
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Cool circuit!
Sounds cool too
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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.
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Awesome Lauri. Thanks for sharing.
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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.
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Ciao Lauri
intriguing circuit :smiley:
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Which is the value of R1 ? Is it the "standard" 1M resistor ?
Thanks
K
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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.
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Thanks Lauri
K
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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/octaversch.png)
http://www.kolumbus.fi/~kp5188/musiikki/octaverpic.png (http://www.kolumbus.fi/~kp5188/musiikki/octaverpic.png)
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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
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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.
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I understand, OK
Thanks for the answer
Franco
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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 (http://www.kolumbus.fi/~kp5188/musiikki/flipflop2.png)
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> 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.
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Hi Lauri,
a little bit late to the party, but would you be so kind to repost the schematics for the octave-down effect? The links are not valid any more.
Cheers
willi
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I've lost the schematic for the whole thing I built. I was able to find schematics for the basic tube octaver circuits.
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Thank you very much!! :worthy1:
What voltage would you use for B+? 300 V?
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Anything between 200-350V should work just fine.
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I've lost the schematic for the whole thing I built. I was able to find schematics for the basic tube octaver circuits.
Sounds good. Are you sure that first schematic (octaver.png) actually works???
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Sounds good. Are you sure that first schematic (octaver.png) actually works???
That's the circuit in the octaver in the video.
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Anything between 200-350V should work just fine.
Very convenient, this means I can use my booster instead of building a power supply.
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Sounds good. Are you sure that first schematic (octaver.png) actually works???
That's the circuit in the octaver in the video.
I suppose the volume pot goes after C11.
Where did you place the gain? Next to R5?
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I suppose the volume pot goes after C11.
Where did you place the gain? Next to R5?
Low pass filter goes after C11. There's a amplifying stage for the clean signal and a mix circuit but that's the part of the schematic I've lost.
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Here's a full schematic for a tube octaver. Some resistor values might need adjusting depending on the supply voltage.
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Oh, so this is an amp with built in octaver effect, not a standalone octaver effect...
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Oh, so this is an amp with built in octaver effect, not a standalone octaver effect...
It's a standalone octaver effect.