Help with getting rid of earth induced hum in the AKSA

EchiDna · « **on:** 23 Aug 2003, 07:15 am »

Hi All,
I recently moved my AKSA 100 for a comparison session, upon return it has picked up a ground loop or something similar. All wires and solder points appear to be in good condition, nothing is loose or rattling around, yet if I connect the amp to a mains powered input I get hum...
To test this out I plugged my laptop headphone connection into the amp via RCA, no problem on battery power, dead silent.... but ascending volume hum once on mains with the laptop battery removed!

any ideas guys? Hugh?

The amp has worked flawlessly for months now before my little comparison session (no problem at the session either.. Bleh..)

andyr · « **Reply #1 on:** 23 Aug 2003, 07:33 am »

Mate ... you've been indulging in unprotected comparisons and your amp has now caught something

Next time, when you take your amp to someone's place, wrap it carefully in 'Gladwrap' before you leave your house!!

Andy

EchiDna · « **Reply #2 on:** 23 Aug 2003, 11:13 am »

Quote from: andyr

Mate ... you've been indulging in unprotected comparisons and your amp has now caught something

Next time, when you take your amp to someone's place, wrap it carefully in 'Gladwrap' before you leave your house!!

Andy

if only it was that simple...

Rom · « **Reply #3 on:** 24 Aug 2003, 07:08 am »

Hi EchiDna,

check for the resistor to ground on the input, these may have gone bad when you test your amp hook up to a source which has a common ground.

good luck and hope you solve your problem.

Rom

PS any result of your comparison? just interesting to hear what you found out. by the way I like your set up on your amp big heat sink on each side, I may do one of those one day.

PSP · « **Reply #4 on:** 24 Aug 2003, 08:51 pm »

Hi EchiDna,
I'm not sure if it would induce hum, but along the lines of Rom's post, is there any chance that your RCA shifted during the move and now signal ground is in contact with the chassis?

just a thought...

Good luck,
Peter

AKSA · « **Reply #5 on:** 24 Aug 2003, 10:27 pm »

Hi Glen,

Pardon my tardiness; last night I just returned from a Friday/weekend driving trip to South Australia (460 miles each way).

Peter and Rom could be right; check their suggestions. In particular check R2, the 10R earth float resistor on the power amps and the GK-1.

Check also that all your gear is powered from the same power circuit. Sometimes there are differences in earth potentials due to heavy current draws on other appliances, and this differences will be amplified and show up as hum.

If hum persists, try disconnecting the star earth on the power amp from mains/chassis earth. In some cases (not all) this can help. Try also a little cleaning of the RCAs, and be sure, as Rom says, that none are contacting the chassis; they must take earth reference from the amp/GK-1 modules, not from chassis.

Hope this helps,

Cheers,

Hugh

EchiDna · « **Reply #6 on:** 25 Aug 2003, 08:26 am »

thanks for the tips, will try em out tonight...

Hugh, no stress on your "delayed" response, what is a day between friends huh?

the GK-1 is definitely NOT the source of the problem, I tested the system out with a battery powered cd walkman, no hum with or without the GK-1. My gainclone (usually on my PC speakers) also exhibits no hum with the GK-1 and mains based inputs...

as an anecdote... it was pretty hot and humid the other day and touching the mini plug earth with my finger gave a gentle hum (high humidity, sweaty hands...) anyway, the rca cable was about 5 metres long to my laptop and as I walked across the loungeroom, I noticed the hum changed tone. It seems that marble floors and silk carpets have distinctively different earth properties as I hoped from one foot to the other (marble to carpet) the hum changed from a "weee" to a "woooo" and back again. The wife was rolling around on the floor for ten minutes laughing when she saw me doing that

EchiDna · « **Reply #7 on:** 25 Aug 2003, 03:05 pm »

unbelievable... problem solved...
I was thinking it was odd that both channels developed the same problem at the same time... well my IEC plug had somehow got bent internally and the earth was not connecting to the IEC socket. I tried another power cable and Voila! a silent background once more...

AKSA · « **Reply #8 on:** 26 Aug 2003, 06:53 am »

Glen,

Happy ending to a vexing problem! Congratulations!

Hugh

EchiDna · « **Reply #9 on:** 26 Aug 2003, 10:25 am »

Quote from: AKSA

Glen,

Happy ending to a vexing problem! Congratulations!

Hugh

Thanks as always for your service/support Hugh....

I'll be chasing up that GK-1 remote kit shortly.

Cheers,