A Question About HUM

[Cqwet Dbdfte]

OK, now I know people are not actually reading the discussion before responding. This discussion has always been explicitly about a property in rural Ireland.

I was not responding to you.

 

[ccaudle]

I was not responding to you.

Then why post information which is completely incorrect in the context of the thread?

 

[Cqwet Dbdfte]

Think aboutr

Then why post information which is completely incorrect in the context of the thread?

Think about that...

 

[DaveDC]

Something to try that is safe and appropriate for a musician in rural Ireland who doesn’t own a voltmeter:

1. un-rack the WA273 and place it on a convenient surface. Make sure the chassis is not touching anything metal, since we are trying to isolate it from any conducted interference (per my earlier post.)

2. locate a pair of headphones, preferably high impedance ones like AKG K240s so as to not load the WA’s output too much. Looking at the online picture on the WA site, the WA273 appears to have transformer-coupled outputs, so it should be safe for the phones to have the WA drive them directly.

3. Make a cable that connects the sleeve of the headphone jack to Pin 3 of one of the WA’s XLR outputs, and connects both the headphone tip and ring together to pin 2 of the same XLR. So, two wires: sleeve to pin3, tip and ring together to pin 2. This puts the left and right headphone elements in parallel and driven by the WA in a way that that is isolated from the (potentially chassis-connected) XLR pin 1.

4. install the XLR shorting plug that Ian described into the input XLR input of the same channel as you have the headphones wired to.

5. With the WA's mains power switch OFF, plug the AC mains cord into the same wall socket you usually use. Configure the ground lift switch as you usually do. Confirm that the WA is isolated and not connected in any way to anything else besides the mains cord and the phones (per my earlier post.)

6. With the WA’s power OFF, listen to the phones to confirm that there is no sound, hum or otherwise. It is always a good idea to “proof” your test equipment like this to avoid making dumb mistakes.

7. With the WA’s gain set to minimum, output level minimum, phantom OFF, pad OFF, Mic input selected, and hi-pass filter OFF, turn on its power.

8. Listen in the phones for any hum as you slowly advance the gain and output level. If the WA is working properly, you be able to get the gain and output level to maximum and hear only the hiss of the WA’s natural noise floor, free of any hum.

9. Check both positions of the WA’s ground lift switch. If it hums with the ground not lifted, there could be an issue with the mains power. Unfortunately, I am not expert enough on AC wiring standards in Ireland to help much with this.

10. If you do hear hum, I think it is safe to say that the WA is not performing as intended when installed in your studio. Since you already had the unit checked okay by a qualified tech, pretty much the only conclusion is that there is something amiss with your mains power.

11. Have a *qualified* electrician check out your facility’s AC mains installation. Look for improper voltage (230 VAC +/- 10% typically), dodgy safety earth connections, etc.

Please report back on what you find so we can help you with next steps.