Question(s) about noise from old amps

[russ74]

In my Hi Fi system I use a number of vintage amps swapping them every few weeks. One thing I have noticed using my old Rotel and Leak receivers is a loud intermittent static like crackle when listening on a variety of sources, this never happens when I use my vintage JVC or modern NAD. The crackle sounds similar to removing a fleece jumper but amplified through the speakers.From left to right my set up is:Speaker - Desktop PC/Monitor on small coffee table - Hi Fi rack - SpeakerBoth the Rotel & Leak have all din inputs and outputs, 5 pin for input and 2 pin din for speaker connections, both have wooden covers with no metal lining. When used they both sit on the top shelf of the Hi Fi rack due to size.The crackle is independent to the volume and on both amps the volume pots are clean - no noise when I turn them, the Rotel has some noise on the other switches the Leak doesnt (It was serviced by the previous owner). There is also no hum so it's probably not a ground loop. Originally thought it was the PC but crackle still occurs with it switched off, haven't determined yet if its from another external source. Also they don't pop & crackle as if a transformer, cap etc is on the way out and there is no channel drop, 90% of the time they sound great. When used both are plugged into a belkin surge protected multi plug extension.Not sure if cables may be an issue but I use a din - rca interconnects & supra classic 2.5mm speaker cable (2 pin din plug (amp) - banana plug (Speaker)), the same wire is also used as the speaker jumper.As I say this crackle only ever occurs when I use the Rotel & the Leak. I don't have any pictures of the amp but heres a couple of links to give an idea.Leak 3400:Leak 3400Rotel RX-802:Rotel RX-802I know the Leak is a rebadged Rotel as a quick look inside confirmed - same pcb boards and layout. This static noise has me flummoxed as it only occurs on these to amps.Any help/insight would be much appreciated. Aplogies for waffling on a bit.

 

[fatboyslimfast]

Have you got heating/fridges etc switching on and off? My RA-820 is particularly susceptible to this and I get "pops" about every 1/2hr or so...not enough to annoy, as it's my spare system...

Interestingly, even when using the same ancillary equipment (speakers, cables, source etc) with my old technics reciever, I get none of the popping. But also a lot less detail

 

[russ74]

They are used in a small room above a kitchen & are near a radiator plus the central heating main gubbins are quite near in the master bedroom separated by a bathroom. Had the amp on normal volume on aux 1 (CD player) without any music playing. Central heating is off and have noticed a few crackles/pops when the pc gets active.Had the top off the Rotel and had a good mooch with a torch, nothing amiss, no bulging caps, loose wires etc. speaker select switch looks a little dirty, couldn't really see the other pots but they're not noisy.I'll put the Leak in place later on and do the same. I'll look inside the Leak but I know this is spotless, whoever serviced it did a good job.So got to assume it's external interference.

 

[russ74]

OK an update. Swapped amps to the Leak and very little noise, faint crackle every 30 minutes or so but would not be audible with music on.Going to move the Rotel to another room and see if there's any difference in noise though it looks like it may be an issue with it after all. Even with the odd loud crackle its the best £20 amp I've heard especially FM. Looks like a proper service may be in order.

 

[russ74]

Finally may have got to the source of the problem. Had the Rotel set up in the lounge and back room. Minor crackle in the lounge but nothing in the back room which rules out stuff in the kitchen. Moved the receiver back up stairs plugged everything in and it's back, can only assume its to do with the central heating control.Also did a thorough check of the interconnects and found one was letting in a lot of noise when it was plugged in. Can only assume it's not shielded very well. Shame as it's a nice sounding cable from a reputable maker on eBay. Is there anything I can do to improve the sheilding of this cable such as extra sleeving or will ferrite clamps help? My other eBay cable (different maker) is fine. May have a go at making my own DIN - RCA cable.Also the interference was much more noticeable on the Aux 2 socket & the shielded cable picked up interference when plugged in here. Is this down to the socket being dirty? I have some switch cleaner but haven't a clue how to clean a female din socket.Cheers for any help offeredRuss

 

[bobdupuy]

I am having a similar problem with my new setup in my office. I just purchased two Monitor Audio Bronze BX2's and hooked them up to my old Onkyo TX-NR600, which was working fine when I retired it from my HT system a few months ago. My input source is my PC using Spotify, Pandora, vTuner, etc., or the DVD in the PC. The connection from PC to Receiver is a high-quality shielded cable.

The sound is great, but at random intervals, I get a very brief interruption of static-crackle, probably 1/4 second in duration. The timing of the interruption seems unrelated to the content of the music being played. I thought it might be the Internet music, but the same thing happens with CD's played on the DVD. I want to rule out the speakers being the source of the problem since I have only 30 days to return them. The Onkyo is the main suspect. I have no hum or any other kind of noice except this static. I am just looking to someone who can confirm that.