I have acquired a noisy amplifier. There's a constant background sound reminiscent of an FM radio without an aerial. There no sound with volume at zero.
Any ideas?
Any ideas?
Make and model and is it one or both channels faulty.
If turning the volume down removes the noise then it sounds like a preamp issue... but we need much more detail to advise.
If turning the volume down removes the noise then it sounds like a preamp issue... but we need much more detail to advise.
So an active speaker...
If the noise is controllable via the level control then it points to a front end problem, whereas if the noise is an all or nothing thing then could the power amp stages be being automatically powered down which some designs do when there is an absence of signal.
So I wouldn't like to begin to even guess without seeing circuit details tbh.
If the noise is controllable via the level control then it points to a front end problem, whereas if the noise is an all or nothing thing then could the power amp stages be being automatically powered down which some designs do when there is an absence of signal.
So I wouldn't like to begin to even guess without seeing circuit details tbh.
Do You mean Hiss ?
Hiss is normal for an PA Speaker when in high gain or level mode.
Some speakers (Behringer for ex) assume MIC gain level when pot is above 12 O'clock
What happens when You short the input ?
Have you tried shorting the input? I.e. connecting the RCA centre conductor to the RCA shell? Without it, you're hearing the noise of the input impedance, which could be on the high side (47-100 kΩ typically).
Tom
Tom
In order: (1) The noise increases or decreases in line with gain setting. (2) It is not hiss - more like static. (3) Shorting the input results in no change.
New symptom: the problem seems intermittent. The amp has been on for an hour with no input signal. The noise eventually reduced to virtually inaudible.
I am unable to find a schematic for this model (MK3). A schematic for a MK2 is attached.
New symptom: the problem seems intermittent. The amp has been on for an hour with no input signal. The noise eventually reduced to virtually inaudible.
I am unable to find a schematic for this model (MK3). A schematic for a MK2 is attached.
I can only see a block diagram in that manual unfortunately.
As with anything, the first step is to check the supply voltages and make sure they are clean.
If the problem is worst when cold then you might have some luck with freezer spray to narrow things down (a cheap can of butane based air duster used inverted works well as a substitute)
As with anything, the first step is to check the supply voltages and make sure they are clean.
If the problem is worst when cold then you might have some luck with freezer spray to narrow things down (a cheap can of butane based air duster used inverted works well as a substitute)
An update: I've been listening for a while now . . . It's like being at the seaside. The interference randomly comes and goes.
The only way to stand a chance of fixing it is to get in there and look, inspect and do some basic tests.
It's all good. I've no intention of fixing this problem. I like to recycle. Occasionally I come across an item that may be as easy fix (for somebody else).
This unit stands me at around $10 ($150 retail). My only means of input is via a computer, the output signal is not that of a mixing desk. There is a chance the background noise may not concern somebody else.
If I pass the monitor onto another party I do not want the monitor to (a) fail in the first 45 minutes, or, (b) Burn their house down!
This unit stands me at around $10 ($150 retail). My only means of input is via a computer, the output signal is not that of a mixing desk. There is a chance the background noise may not concern somebody else.
If I pass the monitor onto another party I do not want the monitor to (a) fail in the first 45 minutes, or, (b) Burn their house down!