Any tips for designing/building low noise preamps ?

[rayma]

5532s with no compensation caps across Rf? Are you sure the outputs are not oscillating at some high freq?

They do not require compensation (internal), and are unity gain stable.

 

[babadono]

Mmmmmkay....my experience has been different. Stabilizing opamp circuits is sometimes difficult.

 

[rayma]

Proper pcb layout must be observed, as with any wide bandwidth circuit.

 

[MarcelvdG]

When the feedback network impedance is too high, the pole caused by the op-amp negative input capacitance might destabilize it.

 

[Ivna]

My experience is related to making tube based preamps.
For the lowest noise, I use an external power supply, DC heaters, and SMPS based PSU. I'm of the school that even with all the gain in the world, a preamp playing nothing should be silent at full blast, and I have accomplished this but only using external PSU.

Since you posted in the solid state area, I suggest using batteries for the lowest noise. A pair of 9V batteries gives 18V which is more than enough for the output of a pre I think.

Yeah, I always prefer to use external PSUs. In this case I used +-12v from a PC power supply.

I thought about an old databook I used to rely on from National Semiconductor called "The Audio Handbook" and low and behold I found a PDF on the web..you might enjoy..lots of cool stuff for us nerds.
http://bitsavers.trailing-edge.com/components/national/_dataBooks/1976_National_Audio_Handbook.pdf

Thanks, books like these help me a lot

 

[Ivna]

I had problems once with a ne5532 diy pedal that oscilated when the input jack was disconected...

Proper pcb layout must be observed, as with any wide bandwidth circuit.

Short feedback paths and separated IN and OUT pins, right?

 

[rayma]

I had problems once with a ne5532 diy pedal that oscilated when the input jack was disconected...
Short feedback paths and separated IN and OUT pins, right?

Go by the data sheet layout illustration, using surface mount parts with a ground plane.
Impedance levels must be low as well.

 

[Ivna]

Go by the data sheet layout illustration, using surface mount parts with a ground plane.
Impedance levels must be low as well.

Ok

 

[fubar3]

Preamp power supply https://sound-au.com/project05b.htm