SSL 9K hissssss...

[scott2000]

isn't shielding only a concern when we talk about hum?

Hum ,Buzz and Noise are all fair game

 

[moamps]

....When I connect the microphone directly there everything is ok, nice sound, not his at all. However, when I plugin a microphone cable the hiss rises a lot. Also, with a long cable (10 meters) I get distortion in the unit. ..

Test it with connected shields of the short cables for gain pot to the ground.
Also try it with added small caps of 100-500pf from input pins to ground.

 

[bernatvm]

Test it with connected shields of the short cables for gain pot to the ground.
Also try it with added small caps of 100-500pf from input pins to ground.

I don't understand. Do you mean connecting the chasis of the potentiometer to the ground?

 

[moamps]

I don't understand. Do you mean connecting the chasis of the potentiometer to the ground?

As I see, the short cables you are using for connecting potentiometer are shielded. Where is this shield connected?
If it isn't connected to the ground, connect it. You have obviously problem with stability/oscillation of the preamp. One of the cause can be positive feedback/coupling between stages because that shields on cables aren't grounded. 

 

[bernatvm]

They weren't connected but doing it didn't change the behaviour. The caps in the input rised the noise. I think I'm gonna wait until i have them racked for further troubleshoting.

 

[bernatvm]

Okay so... not in the metal case yet but wired 2nd channel and same behaviour. With the long cable, a part from hi level hiss, I get the mic signal distorted, as if I was saturating the preamp's input.

Without the cable starange pot response (imagine it going from 0 CCW to 10 CW):
- 0-1: Mic saturated
- 2-7: Gain increasing, clean sound
- 8-9: Saturation again at lower volume than what I got at 7
- 9-10: HUM

Also, I have to wait like 1 second for the preamp to get stable when I move the pot.