I found this speech compressor while looking for something else.
Might be useful as a guitar compressor.
(http://www.swtpc.com/mholley/PopularElectronics/Feb1968/PE_Feb_1968_pg47.jpg)
(http://www.swtpc.com/mholley/PopularElectronics/Feb1968/PE_Feb_1968_pg48.jpg)
(http://www.swtpc.com/mholley/PopularElectronics/Feb1968/PE_Feb_1968_pg49.jpg)
It's easy tor read PE JPGs by changing the page number of the above links :)
mac
I actually built one of these and adapted it for guitar back in 1968.
It worked OK, but was a little too heavy handed in compressing for my tastes now. It over-clamped the signal to a slightly lower level than after the signal decayed a bit.
Still, it's useful, if quite complex.
I'm guessing here but by the age of it,the tape application.
I assume it was intended for use with a ribbon or crystal mic right?
My 1973 Sams Transistor Substitution Handbook lists the ECG102A and SK3004 as subs for the 40395, and BC107B/108 and ECG123A as subs for the 2N2925. There are other subs listed but those would be the more common and obtainable....in case heavy handed is what you want.
Things I'd tweak:
- time constant given by R11 and C9
- R10 and/or R12 to have some control over gain,
or make R14 a pot, connecting C10 to the wiper.
- R13 to fine tune bias
mac