AMEK2500 preamp Troubles

[bolotov]

noise is audibly also with the attached mic,
it is all the same whether resisted is or mic

 

[Samuel Groner]

Is the noise proportional to gain--i.e. if you lower the gain by 10 dB, you get 10 dB lower noise as well?

Samuel

 

[bolotov]

if I switch gain down, then also noise lower

 

[Samuel Groner]

And you are sure that you used the right value for R5/R6/R11/R12/R17? What transistors do you have for T1-T8?

What happens if you switch phantom power on/off?

Do you have a scope to check stability? Probably not the problem, but just to make sure.

Samuel