SSL 9K hissssss...

[Neeno]

Hi ppl !
I've solved most of the noise problems mounting my 4 ssl preamps inside a rack unit, i've connected them with star ground and i've also changed the transformer for a toroid 20-0-20 and now they sounds clean and noise free... :grin:

Now i have a hiss problem, only when nothing is connected to the mic input. The hiss is terrible loud...

Anyone can help ?

Neeeeeeeeeeeeeeno

 

[BYacey]

This is normal for a lot of preamps. When the input isn't loaded with a low impedance source such as a mic, the noise goes up.

 

[Svart]

does the hiss change when you turn the gain up/down?

 

[Neeno]

[quote author="Svart"]does the hiss change when you turn the gain up/down?[/quote]

yes... it changes if i turn the gain control...
do you know ho to solve this issue ?

 

[Gus]

Try a 1K resistor from 2 to 3 and see if the noise drops.

Transistors can become hiss generators if the junctions get "hurt"

 

[Svart]

check the C/R networks before the input transistors too, make sure they are the correct values.

 

[Neeno]

I've placed a 2k2 resistor between pin2 and pin3 on the input xlr connector. And i solved the input hiss problem, but now i have almost the same problem when i power off the unit... no hiss but hum, it seems a ground problem, even if all the boards are grounded to the same point and i'm sure i don't have any ground loop inside the box...

any suggestion ?

Thanks a lot for your help guys !!

Neeeeeeeeeeeeno

 

[Gus]

phantom on or off? phantom on with power supply ripple can cause your hum. Check the supplies with a scope.

 

[Neeno]

i get hum when the unit is off....

 

[BYacey]

Sounds like perpetual motion or something like that...
Is the hum coming from the next piece of equipment being driven? If it is humming when the SSL is powered down, then this sounds like a grounding problem.

 

[SSLtech]

The original preamp in the console has a set of optional resistances that can be switched in between pins 2 and 3 to provide alternate impedances. Try a couple of resistors, like 1.5k, 560Ω and 200Ω.

Keith

 

[SaMpLeGoD]

Hello, I know this topic is old, but I finished my SSL9K, just one channel of 4 that I want to build, and I get a little sad with the noisefloor of it... there is a hissssss that become louder with the gain...
I'm using JLM Go Between + DI.
Connecting a Mic, I think the noisefloor is hugier than my Neve 1290 that's dead quiet... althrough I separarte the PSU from the main box (I have the psu outside) I connected the pins 1 to the ground as used to be. One guy told me that maybe there's a problem with the MAT02... maybe they are not propertly matched... humm.. too strange I think.
I need to test in my studio... but at first sight, didn't like it
That resistors across pin 1 and 3 can solve this hiss problem without interfering the gain? Is there any inconvenience doing that?
Any ideas and experiences?

Cheers,

Eddie  :-\

 

[Svart]

There can be a hundred reasons for hiss/hum/noise.  I didn't match my mat-02s and I don't have a hiss problem.  I wouldn't worry about that.

That resistor can affect gain.  I believe that you have a different problem here.

Can you tell us a little more about how you built the unit?

 

[3nity]

the MATs are already matched transistors isnt?
i dont think its that...

 

[Svart]

yep you are right, I was thinking of something else.

 

[SaMpLeGoD]

Hi! I tested yesterday in my studio, there's a slight humm (50Hz)... it's just a simple ground issue I can manage... about the hissss, it is there in extremely gain values... actualy at this time I don't know if is a real problem with something or if it it some SSL9k's characteristic. It sounds good, but a little bit muddy... I'll compare with a friend's one so I can tell the differences... I builded mine with JLM Go between plus Fet DI and substitute the pot for a 24 pos dual gang rotary switch (2x 2.5K log).
Work fine...
I'll compare and will post some photos!
Cheers,

Eddie 

 

[bernatvm]

It's an old thread, but let's give it a try...

I finished my first ssl 9k preamp out of two and I have strange hiss behaviour. I have a short xlr female connector wired into the preamp for testing. 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. Is like if the longer the cable, the higher the gain it is providing...

Also, I'm running everything +-17V for testing RN

I attach a picture.

 

[radardoug]

So you have the board just sitting on the bench, no shielding? What do you expect? Put it in a shielding box before you make final judgements. Its a 60 dB gain preamp.

 

[Ricardus]

So you have the board just sitting on the bench, no shielding? What do you expect? Put it in a shielding box before you make final judgements. Its a 60 dB gain preamp.

More like 75.

 

[bernatvm]

Sorry for t'he noob question, but isn't shielding only a concern when we talk about hum?