Yesterday I noticed something while recording the output of my rehearsal mixing desk into Sony Soundforge. Soundforge gives you a constant monitoring of the level of signal coming in in a detailed way. As soon as I routed the main outputs of my soundcraft spirit folio desk to the inputs of my soundcard, it showed a level of -71.8 db. When I unplugged the desk from the inputs, nothing showed up, so it's no noise picked up from the cables to my soundcard or interference within my computer. No fader was up on my desk, no phantom power enabled, nothing. It was just self-noise from my mixing board....

Is this possible? Can a mixer really show up a background level of -71.8 db? Or is something wrong with mine?

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"Do not fear mistakes. There are none."
Miles Davis

Sounds about right for an analogue board that is not engineered to a very high standard (Neve/SSL land). It's actually fairly quiet compared to some!

You will have some influence over it if you are able to mute unused channels, which would be good practice as a matter of course. If you don't have mutes the self-noise of each and every pre-amp on the board is being summed, and it all adds up. Look out also for things like EQ boosts left in place on unused channels.

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Dynamite with a laser beam...

It sounds about right - the mixer is about the weakest link in the recording chain and adds the most noise.

It also depends on how the gain is set and what the EQ is doing (by-pass the EQ if possible to get the noise down).

That's why I only use a mixer when I have to and use the quietest I could find.

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John - Sound-Link ProAudio
President - Federation Internationale des Chasseurs de Sons

Depending on the type of connections, a noise floor of 70db is not unexpected. Many unbalanced connections are noisy - unbalanced inserts are a major pain in getting a good noise floor. IIRC, most of the modern mixers have a noise floor in the -90s or better, but older ones may have higher readings. However, it's still not really desirable so it may be worth checking out how everything is connected.

Obvious point to consider : is you gain structure correct throughout all the signal path? If there is too much gain in one area, then it may raise the noise floor in the subsequent path. I'd also check to see if any inserts are plugged in (though you may get a spanking from the studio owner if you pull them out).

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Veni, Vidi, Aesculi
(I came, I saw, I conkered)

Ok thanx guys.
I can't mute signals or bypass the EQ (it's a budget desk), but i'm glad to hear that this is fairly normal. I usually bypass the desk for recording and go straight into my soundcard, so it's not an issue for recording (only for vocals do I use the pre-amps because I like them on our singers voice). It does make me think about my monitoring chain though, because I use the desk also as a big monitoring controller...
I have a sm-pro audio IN5 coming to me from ebay, that can also be used as a monitor controller, i'll check if that's any quiter, and otherwise it will have to be a SM pro M-patch2.

Anyway, thanx a lot for setting my mind at ease.

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"Do not fear mistakes. There are none."
Miles Davis

Yep, as other have said, sounds about right, so just carry on making music. Don't let your eyes make sound decisions for you.

Tony.

How close is the desk to clipping when the input reads 0dB? You might gain some more dynamic range by matching the operating levels more accurately.

Cheers

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

If you have bus or main out inserts, take the audio from there, (TRS 'monoed') and miss out the noisy summing-amp.

I did this with a Spirit Live Mk1 and got much better results.

G

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PA stuff on FB

Quote Guy Johnson:

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If you have bus or main out inserts, take the audio from there, (TRS 'monoed') and miss out the noisy summing-amp.

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??? - I think you mean avoid noisy balanced output stages - if you avoided the summing amp then there's no way you could have more than one input channel coming out of the main inserts.

The other tip that I would add is to avoid having any unnecessary channels routed to the output you are using - even if they are turned right down they could still add a small amount of noise to the output.

Cheers

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Tnx for the tips guys, but I think my mixing board is not as flexible as should be...there's no way to take any of the channels out of the main out, no routing to busses or mute or anything. Also no direct outs on the channels. There is an insert for the main bus that could be used as a direct out, but on this particular desk, that one output is not functioning properly (accumulated dirt and dust I suppose). As I said, it is old, but I like the sound of it.
I will look into the whole gain structure again, I think I got it as good as it's going to get, but it never hurts to look again.
Anyway, it's not a major burden, since it's not going anywhere in my recording chain unless i'm recording vocals (and then i'm using a AUX send to route to my computer), and even for that it's going to be replaced by a better pre-amp very soon. And for monitoring the return from my computer it's getting replaced in the next few days. So basically, it's for monitoring my synths before I record them, for rehearsals, for quick checks etc...

As long as I know it's not broken, i'll survive. But I will take all your tips close at hand and look at the whole structure again. Thanx anyway lads.

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"Do not fear mistakes. There are none."
Miles Davis