Yet one more Octave up....

[brett]

Hi.
There's another thread around here about op-amp octave up.  It involves a circuit that's a bit more complex than this (The Cicada).  This one has high input impedance and reduced gating because of the jfet booster.

Here's my take...



If you have a low-level signal (such as from a single coil pickup), you might wish to parallel the 2.2k resistor on the jfet with a 4.7uF cap.  That'll lift gain and sustain a lot.

cheers

PS What does it sound like?  It'll give anything from 0 to 90% of very clean octave.  IMO it sound as good (maybe not as wild) as a Tyco and better (more sustained octave) than a Bobtavia or Neoctavia.

[petemoore]

Great Name for an Octave.
 I bet it does that well...looks pretty easy to do and get parts for.'

[jmusser]

Brett, all I'm getting is an X for the Cicada (great name). Would you post the link for it? The only other name I know that's more appropriate, is "Grandma Smith", but you'd have had to hear her scream at you to really appreciate it! :lol:

[brett]

Hi again.

Here's the link;
http://members.optusnet.com.au/~jethro.dog/mypic158.jpg

Oh yeah, I might just clarify the setting up of this thing.  Turn the "Octave" pot to 10/10, then adjust the 100k trimmer for maximum octave (not 1M - there is no 1M).  For some reason, the *exact* spot varies a little with frequency, so I set it for maximum octave for a frequency of about 800 Hz.  This is approx the G string at the 12th fret.

For those interested in modding the design, a good one would be to roll off some of the high-pitched ringing and ear-piercing harmonics (>~8kHz ??).

cheers