mixer hiss

sellyoursoul · 24th November 2009, 02:00 AM

i'm wondering what the possible causes of hiss are in an audio mixer. i have an older mixer that has an unacceptable amount of hiss. i set all channel faders and gain to zero, but the hiss is still there on all outputs - headphone, main outs, aux outs. the hiss does increase when output levels are increased. can a power supply cause hiss?

Nigel Goodwin · 25th November 2009, 06:47 PM

Normally hiss comes from the front end., if it hisses with faders and gain at zero, then it's got to be later on in the circuit. A circuit, or even a block diagram, would be useful - so you can work out where it may be coming from. Is it on both channels?, if so you're looking for somethijng common to both.

It may be worth scoping the HT rails, see if there's noise on them.

chris661 · 6th December 2009, 08:18 AM

The tone controls (assuming is has some) would be a good place to start.

If it's everywhere, could it be the 0V line has got polluted?

Mooly · 6th December 2009, 08:50 AM

Hiss is broadband white noise and will be caused by the circuit design itself.
It won't be the PSU

If it's an old design it may use transistors in a very basic arrangement for the active stages... or it may use opamps. Would have to see circuit.

But noise (hiss) is caused by the active devices and the cummulative effect of amplifying the noise from all the gain stages.

godfrey · 6th December 2009, 10:45 AM

If it's very old, some of the components may be deteriorating.
Especially resistors, capacitors and potentiometers as well as switches and connections.

TheSeekerr · 6th December 2009, 10:51 AM

What brand is the mixer? Certain brands are notorious for producing junk designs (Behringer, American DJ).

24th November 2009, 02:00 AM	#1
sellyoursoul diyAudio Member Join Date: Feb 2009	mixer hiss i'm wondering what the possible causes of hiss are in an audio mixer. i have an older mixer that has an unacceptable amount of hiss. i set all channel faders and gain to zero, but the hiss is still there on all outputs - headphone, main outs, aux outs. the hiss does increase when output levels are increased. can a power supply cause hiss?

25th November 2009, 06:47 PM	#2
Nigel Goodwin diyAudio Member Join Date: Jul 2005 Location: North Derbyshire	Normally hiss comes from the front end., if it hisses with faders and gain at zero, then it's got to be later on in the circuit. A circuit, or even a block diagram, would be useful - so you can work out where it may be coming from. Is it on both channels?, if so you're looking for somethijng common to both. It may be worth scoping the HT rails, see if there's noise on them. __________________ Nigel Goodwin

6th December 2009, 08:18 AM	#3
chris661 diyAudio Member Join Date: Feb 2008 Location: Lancashire Blog Entries: 6	The tone controls (assuming is has some) would be a good place to start. If it's everywhere, could it be the 0V line has got polluted? __________________ iPod Touch (playing LossLess) > 4th order LR crossover @80Hz > Amp-6b > Fostex FE126eN in folded ML-Voigt Pipes ------------------------------------------------------------> Samson Servo 240 > W6-1139SG Tapped Horns

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6th December 2009, 08:50 AM	#4
Mooly diyAudio Member Join Date: Sep 2007	Hiss is broadband white noise and will be caused by the circuit design itself. It won't be the PSU If it's an old design it may use transistors in a very basic arrangement for the active stages... or it may use opamps. Would have to see circuit. But noise (hiss) is caused by the active devices and the cummulative effect of amplifying the noise from all the gain stages.

6th December 2009, 10:45 AM	#5
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	If it's very old, some of the components may be deteriorating. Especially resistors, capacitors and potentiometers as well as switches and connections.

6th December 2009, 10:51 AM	#6
TheSeekerr diyAudio Member Join Date: Jan 2008	What brand is the mixer? Certain brands are notorious for producing junk designs (Behringer, American DJ).

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