Signal to noise ratio -how to work out ?

Discussions on sound production outside the synthesizer such as mixing, processing, recording, editing and mastering.
Post Reply
User avatar
snod_donkey
Junior Member
Junior Member
Posts: 248
Joined: Tue Aug 05, 2008 1:45 pm
Gear: Moog Minimoog - SCI Pro-One - Roland Sh-101 - Yamaha XS6 - Oberheim OB-Xa - Roland TD8 - Evans super Echo Tape Loop - Memeory Man Deluxe

Signal to noise ratio -how to work out ?

Post by snod_donkey » Wed Nov 09, 2011 3:51 pm

I am trying to work out the signal to noise ratio of a valve preamp unit i have....

I am rather unsure how to do this but this is what i do know

With the preamp input and output controls all the way up i get - 52 db noise output into 10k load with no audio input
With 0.003 mv at 1k hz on the mic input i get 1.1 volts out so a gain of around 52 db i think

Can the signal to noise be worked out from this?

thanks

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Signal to noise ratio -how to work out ?

Post by Stab Frenzy » Wed Nov 09, 2011 4:17 pm

That's not an accurate picture though because in use you would never have the input and output controls set like that.

To measure accurately make sure the output impedance of your test tone is low like a mic, or better yet run your test tone into a mic and then into the pre. Set the gain so nothing's clipping, get your level to about -12db (I'm assuming you're running into a digital system) and then stop the signal but make sure your input impedance doesn't change. Measure your noise level now, add 12 (or whatever your signal was at) and that's your signal to noise ratio.

User avatar
meatballfulton
Moderator
Moderator
Posts: 6055
Joined: Wed Apr 13, 2005 9:29 pm
Gear: Logic Pro X

Re: Signal to noise ratio -how to work out ?

Post by meatballfulton » Wed Nov 09, 2011 6:47 pm

If you're anal about the final number you need to understand "weighted" ratios. More (as usual) at wikipedia.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

Post Reply