New amp produces hum from Torus power conditioner

K

Kenco278

Audiophyte
Ratings
1
#1
I have a Torus 15 amp power conditioner, about 5 years old. It has until now always been silent and problem-free. Typically 9 of its 10 outlets are in use.

About two weeks ago I bought a new Rotel 200 x 5 watt/channel power amp which draws max 1100 watts (=about 9.2 amps) but at idle draws < 1 amp. The power amp is connected to the power conditioner. Both units have substantial manufacturer power cords.

When I turn on the power amp, I hear a soft low frequency hum directly from the Torus unit. The amp itself remains silent. When I turn off the amp, the hum from the Torus stops.

I only hear the hum up to a few feet away. Beyond that distance it isn’t audible.

To make sure no other component is involved, I disconnected everything but the power amp from the Torus and disconnected everything from the amp including the speakers. When the amp is switched on, the Torus hums. When off, the Torus is silent.

I tried the same test replacing the new amp with an older Bryston stereo amp. There is no hum from either unit.

I tried connecting the new power amp directly to the power outlet. The amp is silent. The amp produces no hum when in use, either.

As the hum isn’t loud enough to audibly affect music or other sound, I don’t consider it a serious problem. But I am very curious about it. My uneducated guess is that it’s caused by a slight incompatibility between the two units, not a specific defect. Can anyone suggest a specific cause for the hum?
 
highfigh

highfigh

Audioholic Warlord
Ratings
2,512 8 4
#2
Most power amps don't benefit from surge protection and because they draw so much more current than most A/V equipment, most surge protection devices aren't designed for the load, anyway.

FYI- if you're using balanced cables, try unbalanced- it's not uncommon for balanced cables to have hum, even when the preamp and power amp are close together. I had that with a Krell system and as soon as I connect the unbalanced cables, it was dead quiet.

Shut it down and disconnect the cables from the power amp- if it's quiet, try unbalanced.

BTW- 9.2A would be for 100% efficiency, which that amp isn't.
 
Verdinut

Verdinut

Audioholic Chief
Ratings
274 5 22
#3
Most power amps don't benefit from surge protection and because they draw so much more current than most A/V equipment, most surge protection devices aren't designed for the load, anyway.

FYI- if you're using balanced cables, try unbalanced- it's not uncommon for balanced cables to have hum, even when the preamp and power amp are close together. I had that with a Krell system and as soon as I connect the unbalanced cables, it was dead quiet.

Shut it down and disconnect the cables from the power amp- if it's quiet, try unbalanced.

BTW- 9.2A would be for 100% efficiency, which that amp isn't.
The hum doesn't come from the amp, it's from the power conditioner. That is really strange but there surely is an explanation for it. @PENG would be the person to explain the situation and come with a recommendation.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Ratings
6,904 12 19
#4
I have a Torus 15 amp power conditioner, about 5 years old. It has until now always been silent and problem-free. Typically 9 of its 10 outlets are in use.

About two weeks ago I bought a new Rotel 200 x 5 watt/channel power amp which draws max 1100 watts (=about 9.2 amps) but at idle draws < 1 amp. The power amp is connected to the power conditioner. Both units have substantial manufacturer power cords.

When I turn on the power amp, I hear a soft low frequency hum directly from the Torus unit. The amp itself remains silent. When I turn off the amp, the hum from the Torus stops.

I only hear the hum up to a few feet away. Beyond that distance it isn’t audible.

To make sure no other component is involved, I disconnected everything but the power amp from the Torus and disconnected everything from the amp including the speakers. When the amp is switched on, the Torus hums. When off, the Torus is silent.

I tried the same test replacing the new amp with an older Bryston stereo amp. There is no hum from either unit.

I tried connecting the new power amp directly to the power outlet. The amp is silent. The amp produces no hum when in use, either.

As the hum isn’t loud enough to audibly affect music or other sound, I don’t consider it a serious problem. But I am very curious about it. My uneducated guess is that it’s caused by a slight incompatibility between the two units, not a specific defect. Can anyone suggest a specific cause for the hum?
DO NOT connect power amps to power conditioners. It is not necessary and overloads the power conditioners which is why your power conditioner is humming.

Only devices with fragile microprocessors need any sort of power conditioning device which should ideally be a UPS, and the home have whole house surge protection.
 
highfigh

highfigh

Audioholic Warlord
Ratings
2,512 8 4
#5
The hum doesn't come from the amp, it's from the power conditioner. That is really strange but there surely is an explanation for it. @PENG would be the person to explain the situation and come with a recommendation.
It's usually not coming from, but is caused by connecting the power amp to it. There's always some resistance in connections and when excessive current draw occurs, voltage drops. Coupled with any connection loss, the voltage drop wants to equalize and it does this by using any other connection that exists- usually the audio cables. If the hum occurs between an AVR and TV, it can be heard as hum or seen as hum bars that move gradually up the TV's screen.
 

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