Buzzing. any ideas?

[Colinjg]

I'm getting buzzing from one speaker when my power amp is switched on ONLY when the pre amp is switched off. The power amp is left on standby and switches on when it if fed a signal. It goes back to standby after a few mins if no signal.  However, the buzzing I think is preventing the amp going back to standby if the preamp is switched off.

When I switch the preamp on, the buzzing stops.  I recently reverted to one stereo power amp instead of biamping with two but I'm pretty sure everything is connected ok. I haven't tried putting the 2nd amp back yet.  It is a SS power amp and a Valve pre but not had any problems in 10 yrs +

Buzzing stops when preamp interconnects removed from poweramp.

All sounds great when playing.  Any thoughts please?????

 

[JezR]

I would swap the second power amp in to see what happens, if the problem goes then it's the power amp.

If the problem's still there try swapping the RCA leads over L/R both ends, if the buzzing moves over to the other channel then it's the RCA lead, if the buzzing stays in the same channel then it's the pre amp doing something.

In the mean time I would turn the amp off before the pre. 

 

[Cable Monkey]

Measure for DC leakage when it buzzes.

 

[Colinjg]

Thanks guys for the advice.

Been playing this morning and:

Power amp on: no buzzing when interconnects not connected. Connect interconnects and it starts buzzing EVEN THOUGH interconnects not connected to anything at the other end.   Both power amps behave the same, I'm sure they are ok.

Therefore conclude that interconnects are acting as aerial. 

 So!! is it picking up an airbound buzz from one of the power supplies in the stereo? Preamp no.  Phono stage no. Turntable power suppy no. all switched off.

I then worked my way through every trip switch in the house. The only time it stopped was when I switch off the ring that the stereo is all connected to, including the power amp.  No idea where it is coming from.

Problem 10x worse when using unshielded interconnects. Ok understand that.

Just put back to biamping, shielded interconnects to amp driving main drivers.  Unshielded silver innterconnects to amp driving tweeters.  Can't hear buzzing. But when shielded to single amping there is a buzz. 

Don't really understand but will leave back in biamp mode.  More grunt anyway.

 

[Radioham]

Hi,

Is it near any RF like Mobile Phone, Cordless Phone, Wifi Router, Power Line Adaptor etc.

If the system against a neighbours wall, do you know what on the other side ?

IMHO I would never use un-screened interconnects apart from speaker cables.

REgards

Alan

 

[JezR]

What type of interconnect are you using? if it's a pseudo balanced rca cable it needs to be used in one direction ideally, that may have an effect. 

 

[Colinjg]

Can't find what the source of the unwanted RF.

Cables are homemade screened fairly heavy duty co-axial cable I bought from Maplins.  They  were pennies to make, advertised as 99.999% OFC and sound at least as good as the £200-300 per pair Nordost stuff I had before.  I also have a solid silver Missing Link pair which I think are unscreened that I sometimes use to connect one power amp to tweeters. ( But don't notice buzzing in this config.)

 

[TheFlash]

Did the problem just start spontaneously in a system which had not been changed/unplugged/whatever for some time? Or had you recently changed something (anything at all?

 

[Colinjg]

Started when I took one power amp out of the system. So just a pair of shielded interconnects to one power amp and then biwire to speakers.   Noticed buzzing.

Since put second amp back in and all normal again.   Not sure why.  But problem gone so better stick as I am.

The back ground to this is, ( I had forgotten) that I had to move to screened interconnects when I got my valve preamp about 12 yrs ago because of buzzing. Also found that some of it was due to dimmer light switches in Kitchen and sitting room. I then changed the dimmer switches to more expensive ones and made a big difference.

 

[TheFlash]

Started when I took one power amp out of the system. So just a pair of shielded interconnects to one power amp and then biwire to speakers.   Noticed buzzing.
Since put second amp back in and all normal again.   Not sure why.  But problem gone so better stick as I am.
The back ground to this is, ( I had forgotten) that I had to move to screened interconnects when I got my valve preamp about 12 yrs ago because of buzzing. Also found that some of it was due to dimmer light switches in Kitchen and sitting room. I then changed the dimmer switches to more expensive ones and made a big difference.

Lots of good info here to help narrow down the issue. The dimmer switches may well be the source but it’s how the RF is getting into your system which is key.
On the second amp: when you put this in, you obviously have to modify what’s connected to what... but did you remove any cables from the system when reinstalling the second amp? Just adding, then, or also taking away? I think the former but don’t want to assume anything.
Up to you whether you want to play the explain game of course or just settle back and enjoy!
N

 

[Colinjg]

Thanks for your interest. I'm going to leave as is for about a week just to make sure this set us is ok and the buzzing is not intermittent.  I'll go back to one amp in about a week and do the same.  I can't see why the two set ups would behave differently.

 

[MrLem]

If only one channel does it (and I guess if physically moving the amp doesn't change anything) then it seems likely to be an outright fault.  If I had to take a shot in the dark I'd say the signal ground on that channel had a cracked solder joint or other break.  That's speculation but it would be consistent with the symptoms because when you hooked that channel to a live pre or a second amp it might have been able to use the ground from the other device and become happy(ish) again.  Anyway, I'd suggest going to the single amp config where you get the problem then swapping the other identical amp in.  If only one does it then the amp is probably faulty.

If not then because it's just on one side you can start to try to isolate by switching channels.  The nice thing about everything being stereo is that there are two identical copies of every bit of the chain.  So you could wire the left channel on the pre to actually do the right side and see if the fault moves with it.  Then the same with just the cable from the pre to the power, then with the amp, etc.  It's a methodical way of figuring out which bit is the cause.

It's probably too early to get into this but if you want to check the broken ground path theory it might be worth getting a multimeter and testing to see if one amp input shield has a direct connection to the mains earth pin on the amp itself and one doesn't.  Obviously do that with the amp completely unhooked and unplugged and generally nowhere near the mains.  Someone more knowledgable might be able to point out that I'm barking up the wrong tree, or the amp might have a floating signal ground which would make it inconclusive anyway, but if you've a meter around it can't hurt to try...

 

[uzzy]

I'm getting buzzing from one speaker when my power amp is switched on ONLY when the pre amp is switched off. The power amp is left on standby and switches on when it if fed a signal. It goes back to standby after a few mins if no signal.  However, the buzzing I think is preventing the amp going back to standby if the preamp is switched off.

When I switch the preamp on, the buzzing stops.  I recently reverted to one stereo power amp instead of biamping with two but I'm pretty sure everything is connected ok. I haven't tried putting the 2nd amp back yet.  It is a SS power amp and a Valve pre but not had any problems in 10 yrs +

Buzzing stops when preamp interconnects removed from poweramp.

All sounds great when playing.  Any thoughts please?????

If the problem is intermittent methinks a mains cleaner such as the isotek or similar at the front end of all your equipment might provide a solution .. see if your local friendly dealer will let you try one at home.

 

[TheFlash]

If the problem is intermittent methinks a mains cleaner such as the isotek or similar at the front end of all your equipment might provide a solution .. see if your local friendly dealer will let you try one at home.

It doesn’t sound like it’s that sort of intermittent... it buzzes in certain configurations and not in others. I say this as an Isotek user by the way.

 

[uzzy]

It doesn’t sound like it’s that sort of intermittent... it buzzes in certain configurations and not in others. I say this as an Isotek user by the way.

Good point but if he can lay his hands on one to try you never know   I personally hate it when i have to disconnect and move things about as sods law says it will always create a few problems that results in a lot of head scratching and plugging and unplugging, dressing leads etc. etc, 

 

[Colinjg]

Last night lots of buzzing with dimmer lights on low, all but disappeared when lights on full power or off. Will have another play tomorrow.

 

[TheFlash]

Last night lots of buzzing with dimmer lights on low, all but disappeared when lights on full power or off. Will have another play tomorrow.

Well that sounds like the source is all but confirmed. I presume moving from dimmers to on-off is out of the question!

I am sure I'm not the only other wammer with dimmer switches but I have none of these issues. I have "dedicated" mains back to separate consumer unit - the inverted commas are because cynics say there is no such thing as dedicated if we al go back to the same sub-station down the road... I think it's about degrees of separation. I'm not sure exactly what your dimmer switches are emitting but my first investigation would be to ensure that the hardwired circuits themselves are all suitably separated. I'm no electrician but if you happen to have a new set of bulbs in the house then I'd waste a few minutes trying them, just to check that an end-of-life bulb on partial (dimmed) output isn't the culprit. Thrashing around of course but it might help...

 

[Fourlegs]

Dimmers? What is this new fangled technology? We make do with candles and put out a couple of them out if it is too bright. One rarely gets RF or EMI from candles.

 

[Guest]

Dimmers? What is this new fangled technology? We make do with candles and out a couple of them out if it is too bright. One rarely gets RF or EMI from candles.

the optimum number of candles being 4