annoyingly loud hum

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Hi guys i need help (again) my system has suddenly developed a rather annoying hum, System comprises of CA D500se, CA C500 pre amp, 2x CA P500 Power amps driving Wharfedale diamond 8.4 speakers bi amped & bi wired. it has all been working fine for months but has now developed the hum, doesn't get any louder with the volume and cannot really be heard with music playing but is very noticable in quiet sections.

Any ideas?

thanks Regards Gav
 
Check that mains cables are away from speaker cables- if they run parallel this can induce hum. This is the most likely cause- post-amplifier otherwise it would increase with volume. If your speaker cables must cross mains cables, try and get them at 90 degrees to eachother...
 
Hello, I had the exact same problem and it was solved by replacing the capacitors of the power amp. According to the specialist it is a common problem for some gear.

Bram
 
Can you attenuate the hum by touching any of the grounds on any of the equipment? (Normally you'll find a ground on the case back somewhere - no need to open the cases) If you can then bramdo is probably right. Make sure all the devices are wired the same way around if they don't have earth connections (i.e they are on two pin or ungrounded mains leads). Then try grounding all of your kit to a common ground. Sometimes provides a temporary cure.
 
Hi guys, i have 2 power amps and both producing a hum when turned on, have tried toching the ground on the pre amp but no difference, would the caps go in both amps at the same time?

cheers
 
Hi target rack, set up like this

top shelf cd player

2nd shelf pre amp

3rd shelf power amp

4th shelf power amp

5th shelf mains block

all connected with dnm reson interconnects, all into 1 mains block with russ andrews silencer

cheers
 
Your DNM Reson interconnects are -as far as I can find- unshielded. It is a possibility they may be picking up some mains-hum from somewhere. Might be worth trying some thicker, shielded cables to see if that makes a difference. If you explain this to a friendly local hifi dealer, they may lend you a few pairs for experimental purposes.
 
Think i've got some old qed qunex2 lying around, althought the dnm have been in use for months, have i just been lucky so far?

i'll give the qed a try and see what happens

cheers
 
Gotta be worth a pop before any major work is undertaken! It does sound like mains interference to me. Have you recently bought any new electrical equipment (not necessarily hifi/AV)? If so, maybe something else in your house is pumping some rubbish into the supply. My concern is that the level doesn't change with volume- if the change of interconnect makes no difference then it could be a problem with (as another post has mentioned) capacitors, or even a loose winding in a transformer resonating.

You could also try a mains conditioner to see if that helps. A Tacima CS929 mains block may help matters... I bought one to stop my woofers exploding every time the freezer kicked in. Central heating also used to cause problems- but no longer!
 
just tried the qed, no difference unfortunately, just tried the volume again, does get a little bit louder at 80%+ but not under that. have russ andrews silencer on the system, only other electrical item added was a sony blu ray but noise doesnt quieten down when unplugged.

cheers
 
Hmmm... OK I'm pretty much flummoxed now. Last ditch effort- shielded speaker cables? Again, a friendly dealer may loan you some. I'm all out of advice now, I hope somebody somewhere can sort this for you!

Best of luck, Gav...
 
Hi,

do you have cable television and if so, is your television (or a device that is connected to the televsion) connected with the amp. If so a ground breaker (small device that you plug onto the cable of the televsion ditribution) can also help,

Bram
 
Hi guys,no tv connected on this system or near it, running out of ideas now, over the past 24 hours i've completely stripped it down, cleaned all connections tried different cables, re-installed everything piece by piece,switched all electrical items off in the house and nothing. i'm thinking the problem lies within the pre amp as the hum is apparent on both amps and appeared at the same time,

it has been mentioned to replace caps in the power amps but now thinking the problem lies within the pre so next question is what could be the fault and how do i sort it?

cheers
 
I think your best bet is to have the amp professionally serviced- I would give CA a ring and see what they reckon. The engineers should have a much better idea as to what the fault is.

I'm thinking 'grounding problem', but I don't know how this would occur during normal use! I'd definitely get an expert with a beard and a large multimeter to poke at it with his probes.

All the best Gav, hope you get it sorted.
 
Cheers guys for all replies, emailed customer services at richer sounds and they said to take all the amps down for their engineers to take a look, I'm hoping its not going to cost too much for repairs, hopefully they will quote before doing any work.

what price would you think it would become financially unviable? what amp/amps would give me a similar sound, i would prefer more detail if anything but still in the budget market.

cheers
 
As a quick check before you wheel them off to the engineers it is worth trying to isolate which unit the hum is coming from.PS Audio include a work through in their product manuals for their mains conditioning equipment.If you go to www.psaudio.com and download their product manual for the Quintessence it gives details on how to troubleshoot the hum.

I don't have any connection with them but own a Quintessence!
 
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