Another look at the leaky transistor buffer!
I was looking back at some of the recent articles and it suddenly occurred to me that the AC128 buffer using the leaky transistors that I posted a week ago could easily be adapted to work on a negative ground system.
All we have to do is flip the transistor over and it can be powered from the same supply as the rest of your pedals. Note that there are some slight changes to the ground reference of the pulldown resistors and also the orientation of the output capacitor C2.
The low gain (Av=0.9) will prevent this circuit from causing problems when used in this configuration, unlike what can sometimes be encountered with the high gain fuzz circuits used like this.
Try this simple buffer with your leaky germaniums!
Jack, can the gain on this buffer be pushed up to unity? Does it start to clip? I’m liking the way it preserves all the content in my guitar signal, but would prefer it without the attenuation.
I should have built it with a variable in R4 to play with the gain…
If you’re interested here is the buffer off/buffer on comparison: http://dl.getdropbox.com/u/870088/sounds/name-that-effect.mp3
That’s over a long cable run (~45′) with the buffer sitting mid-way.
You can make the circuit go closer to unity by selecting a high HFE transistor, but it will never get to gain = 1, nor will any simple transistor buffer whether silicon or germanium.
Will this only work with leaky germaniums? cause I prototyped this with 2N3906′s, and i get no sound. Interestingly, though, the amp does respond to me touching the strings and bridge in the usual way. (humming when i’m not touching them, stopping when i do).
Also, i used 10uF polarized caps.
Are “leaky germaniums” necessary or what?