API type summing mixer : Noise issue ?

[hugo]

Hi,
I finished a summing mixer, and i have a question regarding noise generally speaking...
My audio interface (at my "diy lab") is a native instrument Komplete audio 6

-With nothing connected to XLRs, i have about -86dbfs on plug ins.
-With summing mixer OUT connected to Komplete IN (nothing plugged to the summing mixer), i have the curve that i posted :
-65/-70dbfs . All channels are muted (but it does not influence the noise level). The main output is fully CW.

Is it normal, bad result ? If it is bad, how to read that curve to understand the problem ?

Thank you

 

[ruffrecords]

As this is an active mixer the number of inputs will influence the noise gain. How many inputs do you have?

Cheers

Ian

 

[hugo]

Hi Ian, thank you for the reply.
There are 16 inputs on this summing mixer

 

[ruffrecords]

Hi Ian, thank you for the reply.
There are 16 inputs on this summing mixer

OK, so you have a noise gain of 24dB so you would expect the noise to be 24dB higher than at the input. Can you post a schematic so I can estimate the noise resistance?

Cheers

Ian

 

[hugo]

OK, so you have a noise gain of 24dB so you would expect the noise to be 24dB higher than at the input. Can you post a schematic so I can estimate the noise resistance?

Cheers

Ian

Thank you so much for your help..really !
I ordered this project from DIY-Racked, and the guy does not provide schematic 
But in your own opinion, would you think there is an issue there ? Or is it good noise level for professional use ?
All channels have one 2520 opamp, and the noise seems to come from there..
The "tech" of the project did recommend me to change the regulators with bigger models. I will firstly try this.
Hugo

 

[Humner]

I'd expect better and think there is an issue somewhere, most likely issue will be a ground loop.

Feel free to post up a quick recording of the noise floor.

I wouldn't start trying fixes until you know what the problem is.

 

[ruffrecords]

OK, no schematic. You should have connected resistors to the hot and cold pins of each input connector. What value are these?

Cheers

Ian

 

[hugo]

OK, so you have a noise gain of 24dB so you would expect the noise to be 24dB higher than at the input. Can you post a schematic so I can estimate the noise resistance?

Cheers

Ian

There are 2 resistors 40k at the input , but since i did not have my MM, i do not know if they are in series or parallel..

 

[hugo]

The unit is fine, dead quiet when tested with a new interface..the noise was sent to the summing mixer vy the previous audio interface, which was not quiet..
Thank you for your support Ian

 

[ruffrecords]

The unit is fine, dead quiet when tested with a new interface..the noise was sent to the summing mixer vy the previous audio interface, which was not quiet..
Thank you for your support Ian

My pleasure. Glad you got it sorted.

Cheers

Ian