Why does connecting stuff add 19dB to my noise floor?

Immanuel · Post by **Immanuel** » Tue Sep 24, 2002 5:28 am

Why does connecting stuff add 19dB to my noise floor?

I thought, I would give my analog ins a last chance. This is my result:
If I have nothing connected to the cable dongle, my noise floor is at -84dB.
If I connect a cable to the cable dongle, my noise floor is -84dB.
If I connect something in the other end of the cable, my noise floor is -65dB.

I have a Pulsar1 "classic".

Immanuel

orbita · Post by **orbita** » Tue Sep 24, 2002 7:11 am

what are you connecting to it?
it might be responsible for the noise

Immanuel · Post by **Immanuel** » Tue Sep 24, 2002 9:53 am

1) DBX MiniPre balanced out with a handmade xlr -> rca cable

2) Sony TDC-D8 DAT with a factory made stereo mini-jack -> dual rca cable

Post by **garyb** » Tue Sep 24, 2002 11:21 am

pre's are often noisy as the very act of amplifying a small signal means that you are going to amplify noise the same amount(a lot).i won't even comment on the analog outs on that dat............

Immanuel · Post by **Immanuel** » Tue Sep 24, 2002 11:22 am

Also with no power on the MiniPre?

bassdude · Post by **bassdude** » Tue Sep 24, 2002 6:26 pm

Just by plugging it in you are changing impedance characteristics which can affect the noise floor.

Immanuel · Post by **Immanuel** » Wed Sep 25, 2002 2:55 pm

So, do you think a solution would be something like a linedriver, or is there another way for me?

orbita · Post by **orbita** » Wed Sep 25, 2002 3:54 pm

Someone else on these forums recommended Ebtech products for removing hum. Here is their 2 channel line level shifter that increases signal from -10 to +4, makes it balanced and also includes hum eliminator technology to kill mains hum. However it may not remove hiss type noise - that kind you will probably have to reduce with filters and expander/gates.

http://www.audiomidi.com/common/cfm/pro ... ct_ID=1012

jabney · Post by **jabney** » Mon Sep 30, 2002 10:54 pm

Does the DBX pre have an unbalanced out? If so, try that and see if it lowers the noise floor a bit. Ultimately, the cure will probably involve getting a quieter (i.e. more expensive) mic pre, if - indeed - a cure is needed. Depending on where the noise is situated in the frequency spectrum, you may not have that much of a problem. Can you hear the noise?