AMEK 2500 mic pre: how does it work?

[modulay]

Ok.
Thanks Jay.

 

[ilikeit]

hi
my amek works very fine
this the frequency render
in orange the amek
in blue midas XL42

:razz:

i have use a sound device USBPRE

 

[modulay]

How much noisy is this preamp?
I've built one channel and I'm testing it (not still with a correct grounding and enclosure).
In my opinion, noise level is good when mic (modified tube condenser APHEX 460) is not connected to input or when mic power supply is off...but noise level increases a lot when mic is on.

What could be the reason of this?

Grounding and EMC?
Transistors matching maybe?
Inappropiate signal capacitors? (I've used ceramic caps instead of polypropylene)

 

[pedroplanet]

Can someone help me on how the components are placed on the pcb?