Minimal discrete preamp just for kicks

[L´Andratté]

Found this from Jessica Rylan´s personal synth, she is a (now inactive?) noise musician, so take it with a grain of salt, just wanted to put it out for reasons of (real basic) study.

It´s really minimal, with the 75R resistor replaced with a pot, it could approach useable, what do you think?
Not totally clear about that 220k pos. fb?

Found nothing on supply voltage, but I think it is battery powered...

 

[JohnRoberts]

unless this is a joke or argument, it may be in the wrong sub forum.  ;D

Found this from Jessica Rylan´s personal synth, she is a (now inactive?) noise musician, so take it with a grain of salt, just wanted to put it out for reasons of (real basic) study.

It´s really minimal, with the 75R resistor replaced with a pot, it could approach useable, what do you think?

adjustment range is probably limited on low gain end by 1k resistor, high gain limited by open loop gain. You could vary the gain after a fashion but lower your expectations.

Not totally clear about that 220k pos. fb?

the 220k is first establishing the DC operating point for transistors. The connection of bottom of 220k to darlington emitter bootstraps the input impedance making it higher.  The 1M connected to -15x output will also establish DC operating point while lowering  effective input impedance.

Found nothing on supply voltage, but I think it is battery powered...

15k collector load is going to a +V supply not ground as drawn.  Knowing what the +V is only matters if want to build this historical footnote.  :

JR

 

[Walrus]

Almost identical to the Shure M67 mixer input stage......

 

[iampoor1]

If anyone wants 5 of these on a board, Ill send you some Shure M68 mixer PCB's  ;D