humming

[admin_exported]

After many years of stall, I have put my hi-fi back into service , having bought some B&W 685 speakers to replace the old ones damaged beyond repair two years back, linked them to the amp with Van De Hul Snowline cable and replaced the stylus on the turntable. Everything sounded (and sounds) good. But then yesterday I just noticed, while listening to a Bach piano concerto, so no wall of sound stuff, or Led Zeppelin riffs, that there is a repeating hhmmmmm...hhmmmmm, at about one second intervals. Un-noticeable with most rock, faint, but quite discernable though not overbearing, when playing, like for instance yesterday's Bach, any music that has quiet melodic periods.

Turntable is a Trio KD-1033, thirty years old but well maintained, and amp is a Rotel RL-930AX?

 

[Andrew Everard]

The description of the fault suggests some kind of outside interference, but I'd first exclude the turntable as a source of interference by unplugging it from the amp and seeing whether the hum persists. If it does, then it's either a fault in the amp – which seems unlikely to me given your description – or the apm picking up some outside source of interference.

If the hum vanishes, then it's either a turntable fault – again unlikely given the 'rhythm' of the hum – or again something else in the house or vicinity being picked up on the cartridge wiring or the connection to the amp.

 

[The_Lhc]

I had something similar when my other half plugged in some fake flowers with pretty flashing lights set in them (same sort of thing as flashing Christmas lights), they seem to be very noisy on the mains.

 

[tino]

Have you done any tests to isolate the source of the humming?

Do you think it's electrical (interference) or pitch variation in your turntable?

A few suggestion to try:

Amp on, turntable off.

Amp on, turntable on, not playing (just spinning the platter)

Amp on, turntable on, not playing (just spinning the platter), change of speed 33 - 45

Try a different positioning of your mains, interconnects and speaker cables

Interference from any appliances .. you didn't have the washing machine on?

Try a few more different records - is there any warping of the records you are trying?

 

[Anonymous]

Thanks to all for your replies. The sound doesn't appear unless the turntable is playing a disc. However interference could be the factor. I have unplugged the CD player, which isn't working anyway, and it seems like the humming has gone. I'll have to try out another few records and listen again to be really sure. Tried also unplugging other appliances like a lamp and phone but that didn't make any difference.

 

[Anonymous]

For the humming to have a very low frequency repeat, it sounds like the turnatable. At 33 1/3 rpm, the turntable rotates every 1.8 seconds.

Is the turntable solid? or does it have access holes to allow you to fit the belt? If have seen situations where a cartridge would pick up hum from the motor when the hole in the turntable aligned with the cartridge. It had the characteristic hum-gap-hum-gap-hum signature.