Silicon Mk1 Tonebender ?

[blanik]

i've been looking everywhere for a Mk1 silicon schematic,  it seems only Mk2 and 3 where "siliconized" as anywone here ever made one?

i found this online so i guess it's been done...

http://www.musicground.com/product_details.aspx?pid=234

[mac]

I did it this way using 2n2369 NPN low gain silicons, hfe about 70:

Q1: add a 470k resistor from vcc to base to feed it. Emiter should sit at 4v or so. Also 470 from base to gnd, and a 220k from vcc to base might work better, but input impedance should be much lower than the original so you probably need to increase the input cap.

Q2: Replace the 470k with a lower resistor, say 220k and replace the 1k8 with a 22k and use a 50k pot. Collector should vary from vcc to vcc/2. This is tricky.
Add a small pico farad cap from collector to base to roll off highs.

Q3: My best guess is that collector should be at 7v or 8v, so add a 250 trimmer from vcc to base and set the collector near those values. I bet you need a value close to 100k to 120k if using silicons having a gain less than 100.
Do not forget to add the cap to filter highs.

Avoid high gain silicons.

mac