F113 - The dreaded hum

[Steve]

Recommissioning my system today after completing the integration of an additional pre-amp.

Powered up and the right F113 is now humming.

Powered down the system and plugged the F113 into another circuit without XLR to be sure there was no sort of grounding issue or loop.

Toggled the F113 from grounded to isolation.

No change. The sub is otherwise working fine but has a persistent low level hum.

Evidently a fault (power supply module or amp). The other F113 (left channel) exhibits no issues.

I have read about others experiencing this fault.

Not happy. These subs weigh a tonne. Packing and shipping is a logistical nightmare. I have the original packaging in long term storage including the skid but cannot remember how to pack.

Time to call my dealer again.

[Mike]

Steve - try it on the same outlet as what's feeding it (preamp?) to achieve a common ground. Also, is there no separate ground option on the sub? If not, you can perhaps try a make shift ground.

[Steve]

Mike... They do normally run on the same circuit as the pre-amp and are currently connected on the same circuit.

Yes the the amp lets you float the ground by sliding the isolation switch on the rear. I have tried this and are running them set as GROUNDED.

The other F113 is not exhibiting any issues and is dead quiet. If it was a ground issue, the other F113 would be humming/buzzing also.

Have had the complete system unplugged with just the F113 power to mains with no line input.

1. Rear power switch toggle off. Sub is off no noise.
2. Rear power switch toggle on. Front power switch OFF. Sub is buzzing.
3. Rear power switch toggle on. Front power switch ON. Sub is buzzing louder.
4. Buzz is at the same level as 3 with line signal and front power switch set to AUTO. (Out of standby). This is how I always leave the F113s except when we are away for an extended period.

[Mike]

Is it picking up interference from another piece? Try moving it away from the other gear. Try other cables, power and IC.

[Steve]

Sub is not in any proximity of other equipment.

Ok, tried another AC power cord. No change.

Extension lead to another circuit. No change.

Increasing the volume level on the sub does not increase the volume of the buzz except slightly when volume is turned up to max. (No active line signal when doing this.)

Quite audible in quiet/softer passages.

[mep]

Probably the main filter caps in the subwoofer amp are bad.

[Steve]

Probably the main filter caps in the subwoofer amp are bad.

Good call! Dealer agrees. Repair will be covered under warranty.

[bzr]

Could always upgrade to Infrasonics!