Earth loop issue?

From the equipment you list I doubt it would be an earth loop. You seem to have two issues - mechanical hum from the PS units, not uncommon in the Naim world but the low level buzz coming through the speakers is the main worry.

I take it you don't have anything else apart from the CDX2 connected to the 282 ?

A couple of questions -

How is the equipment arranged on the racks and what is your mains setup - hydra, block etc ?

Apart from Burndy and rack changes, did you make any other change ?

Put the XPS Burndy back, does it cure it? The fact that any break in the chain stops the buzzing indicates the cause is near the top of the chain. Since the CDX2 signal earth is through the 555ps but the buzzing stops when just the 555ps is connected points at the CDX2 or the cable connecting it to the ps and you've just changed that cable, putting the old one back will test the CDX2 and tell you if the new cable is suspect.

Hi Guys 

buzzzing remains when I refit XPS Burndy. Only cdx2 is connected via din. I have a dedicated supply with 2 double sockets. No other changes have been made. 

Ok so how are the racks arranged - what's the stacking order ?

If you turn off the 555PS and remove the din lead from the CDX2 and the buzz continues, the issue is with the amplifier. What happens when you do this?

Hi James order is

CDX2           Deck (disconnected till buzzing is resolved)

282.              HCDR (right of the shelf)

Space.          250DR

sky box.       555ps  

HH

if I remove any link 1 in the system (interconnect, snaic, Burndy, mains cable) the buzzing stops. 

The only think I haven’t tried yet is self powering the CDX2. If the buzzing stops, the issue is with the 555 I guess. 

2 more things to try, power the CDX2 directly from the mains with the link plug back in. Do you have a spare Din-Din or even a set of RCAs to replace the DIN with as a test? (Don't forget to chance the output and input selections for the latter.)

Does your dedicated supply have one cable feeding both sockets or two runs from the consumer unit. Scraping the barrel here a bit but if you have a multiblock handy try using that from just one socket and plug the system into it. This is a test not a solution by the way. If the earth impedence is uneven between your sockets that might be a cause so try them all one by one with this set up.

Hi Yeti

ive tried a different din and buzz remains. Not tried RCA’s but can do that later. Supply is one cable 1st socket and then second fed from that. Napsc and 555 in socket 1, HC, 250 in socket 2. 

Sky box? disconnect that until you sort the buzz, it's a bit too much of an unknown.

Some of the tests you are doing won’t help. For example, removing the mains leads from the Hicap or 250 simply turns the system partly off, so buzzing has to stop. If removing the interconnect between the CD player and preamp stops the buzz, the issue lies with the source. So yes, try self powering the CDX2. One other thing - is the Sky box plugged into the same mains socket or connected to the 282? If so, try turning it off and unplugging it. 

Sky box is on the office ring so isolated from the Hifi supply. It’s not connect to the 282 either. Whilst I’m tracing the source of the issue the only source is the CDX2. Will try is self powered tonight and see what happens. 

Yes I'd look at the Sky box first - not sure which one you have but the later Q boxes can cause issues with their Powerline network capabilities.

I'd power that down and see if your buzz disappears before doing anything else.

If that pesky Sky Q box has its ‘Ethernet over mains’ enabled, it can take more than a dedicated mains supply to isolate the HiFi from it, but easily tested by switching it off. If you have a Sky router, maybe try turning that off too, as that may be generating the EOM signal. 

Agree with Chrissu.

When I had my 272 installed, the dealer attempted to install an ethernet over mains hub adjacent to the 272, and it emitted this godawful hum and that solution was ditched immediately. 

Very interested to see what happens here Finkfan because my (new) system is very similar to your own (I have XPSDR on my CDX2, and 2 x HCDRs on my 282). My XPSDR is pretty noisy but has always been so even when it powered my 272.

All the best with getting this sorted. 

The RCA suggestion was only if you couldn't find a spare DIN.

Many thanks for the suggestions 

My sky box is the older 2TB box so no Ethernet over power. It’s plugged into a Tacima extension lead on the office ring and has been for 18 months or so. 

I’ll remove the 10 year old 555ps from the system and report my finding this evening. Looks more and more to me like that’s the culprit and it may be heading to Salisbury for some TLC. No idea what that will cost. 

james n posted:

Yes I'd look at the Sky box first - not sure which one you have but the later Q boxes can cause issues with their Powerline network capabilities.

I'd power that down and see if your buzz disappears before doing anything else.

You should disable the inbuilt powerline adapters in the SkyQ box... I did that with mine as well as disable Wifi and just use Ethernet ... seem to remember settings were in the installer menu...

Stacking order correction

                    P3

CDX2          HCDR (right of shelf)

282             250DR

sky box      555ps

Ok. This morning I disconnected the 555 from the system and ran the CDX2 from its internal ps. The buzz/hum from the speakers increased massively, so much so you could here it anywhere in the room! 

Next thing was to disconnect the Tacima extension lead from the office mains. This reduced the buzz/hum from the speakers back to to the same level when the 555 was connected. I then plugged the extension lead back in. Loud buzz from the speakers returned. I started removing plugs from the lead. Sky box out, loud buzz remained. Plasma tv out, loud buzz remained. P3 smps out, loud buzz remained, phono stage smps out, buzz reduced down previous levels, low, but still there! 

So, before work, I’ll try some repositioning of boxes 

Update

I tried moving the 250 away from the 282. They are currently at the same height, separate racks and 180mm apart. I swapped positions of the 250 and 555. This reduced the buzz slightly. I can now only hear the buzz when the 282 is muted. I plugged the phono stage smps back in to the office ext lead. Louder buzz was back. I removed the smps. Low level buzz back. I then removed the din din from CDX2 to 282. Buzz completely gone! I tried the standard lavender din again. Low level Buzz was back. Din removed, buzz gone again. I then plugged the phono stage smps back in...still no buzz!

By the looks of it the CDX2 is the problem. The buzz from the speakers is much greater when using its internal PS, lower when using the 555 and gone when CD is disconnected from the 282. 

Could this be covered under warranty? It was serviced and new laser mech fitted back at HQ less than 2 years ago? 

Ah so you have a Turntable too which you didn't mention in your first post. If you have the CDX2 connected and disconnect the TT from the 282, do you still get the buzz ?

Sorry James

yes I do. The TT was completely disconnected whilst I trace the fault.

 If I disconnect CD the buzzing stops. The buzz is loud when the CD is self powered. Low level buzz when powered by 555. No buzz when CD is disconnected from 282 

Ah ok - just curious but it looks like you've eliminated that from the setup.

One simple thing to check (you can do this with just the CDX2 on its own (don't connect it to the 282 at this point) is to check for continuity between the earth pin on the mains plug and the one of the outer rings on the RCA output connectors (easier to get to than the gnd pin on the DIN output)

Ok James, thanks. I will check that when I get home this evening. 

So I have a CD555 rather than a CDX2 and am using RCA phono rather than DIN interconnects, BUT I might just have your solution.

Every time I have a power cut or power cycle, I get a hum/buzz.  Fixed in 30 seconds.  All I have to do is go to the Output Socket Selection option (hold disp function in CD mode) and select the right socket type (RCA phono for me, DIN for you).  Even if the right type appears to already be selected I need to reselect it.