Pre amp or power amp hum issues

Batfoon

Well-known member
Feb 13, 2014
3
0
18,520
Hi guys.
Cyrus system and project debut 2 turntable.
Never had issues untill I added 2 power amps and bi amped now i seem to get excessive hum on the phone channel.
Speakers too close to the phono stage or turntable?
Or is there a simple fix I'm missing
 

Gray

Well-known member
1) now i seem to get excessive hum on the phone channel.
2) Speakers too close to the phono stage or turntable?
1) Only the phono input and not on any other source?
2) Why, are the speakers actually any closer than they were before?

Speakers being too close to a turntable could lead to acoustic feedback.

Power amps (with their large mains transformers) being too close to cartridge / phono amp / signal cables could lead to electromagnetic interference - which is more likely to be the cause of the hum you're hearing.
Ground loops cause hum, doubt that's the case for you.
It always comes down to a process of elimination - it didn't hum before, it does now. So what changed? Power amps (and their input signal leads) were added.....
 
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Batfoon

Well-known member
Feb 13, 2014
3
0
18,520
Thanks guys. Yeah since adding the power amps. Had a play this morning. Turn them off everything is good. Turn then on, hum is back.
So moving the turntable and the phono stage further away may resolve it?
I've tried swapping plug sockets but didn't improve things. Turn table is about 2 ft away and the phono stage is sat on top of the CD player. Amps are on the 4 n 5 shelf of the mk 1 Hark stand. Don't suppose moving them to the bottom 2 trays would improve things.
If not I'll have to live with it.
 
Thanks guys. Yeah since adding the power amps. Had a play this morning. Turn them off everything is good. Turn then on, hum is back.
So moving the turntable and the phono stage further away may resolve it?
I've tried swapping plug sockets but didn't improve things. Turn table is about 2 ft away and the phono stage is sat on top of the CD player. Amps are on the 4 n 5 shelf of the mk 1 Hark stand. Don't suppose moving them to the bottom 2 trays would improve things.
If not I'll have to live with it.
Always worth trying to move them further apart. Heavier kit is better off in the lowest trays anyway.
 
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nopiano

Well-known member
A phono stage atop a CD player isn’t a great position ime. Basically it’ll most likely be nothing to do with your speaker proximity, but the electronics.

The phono stage is the most sensitive item by far, and adds massive gain to the tiny signal from your cartridge. So any sources of noise will potentially upset it.

A bit confused about the power amps. Obviously if you turn them off there will be no sound, so that doesn’t really prove anything. If adding them in has caused the change then maybe the earth arrangements are creating a hum loop.

You’re along the right lines by trying alternative sockets. Worth experimenting even if you have to temporarily lash up several extensions just to trace the noise.

Also use the phono stage as a hum sensor. With volume set at loud listening levels but nothing playing carefully lift and move it around to see what changes. But do be sure not to pull out any plugs while moving it or you’ll have different problems. Like Usher cones whizzing past your ears!
 

Gray

Well-known member
...If not I'll have to live with it.
No you won't have to live with the hum.
Just needs experimentation / repositioning that's all.

You do mean a hum from the speakers don't you?
(Because the mains transformers themselves can sometimes be noisy, with buzz/ hum audible at close range).
 

john13

Well-known member
Dec 23, 2013
19
0
18,520
Hi guys.
Cyrus system and project debut 2 turntable.
Never had issues untill I added 2 power amps and bi amped now i seem to get excessive hum on the phone channel.
Speakers too close to the phono stage or turntable?
Or is there a simple fix I'm missing
sometimes situation can be an issue if too near other separates, might also be loose wire somewhere
 

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