[cheviot100]

Here?s my problem. I?ve got a bp26 and a 4bsst plugged into a dedicated line in my living room. The bp26, cd, squeezebox, turntable, cd and tuner are plugged into a good quality Monster cable power bar and the 4bsst is plugged straight into the wall, same socket, upper and lower plugs. Speakers are Spendor s8e models.
Here?s where it gets tricky. I have a b6o as well in my dining room, atop my piano, connected to some baby Spendor s3/5 speakers and connected to the bp26 via tape-out and a very long interconnect to a b60 line in. The b60 is plugged into a different socket in the dining room. All interconnects are of premium quality, the longest between the two amps is an AMX, the rest are Kimber.
When I power up the 4bsst, and the b6o, there?s an interaction, probably some kind of ground loop that generated a buzzy little hum when no source material is playing. It isn?t obnoxious, but I?d just as soon be rid of it if anyone has any ideas.

Thanks in advance, 
Bill

[drummermitchell]

Bill,how long is that interconnect,is she rca.Maybe you need a balanced XLR cable.

[cheviot100]

Good thinking Mitchell and I've considered a variation of this option but don't know what the outcome would be.  The interconnects are about 20 feet rca both ends and I can't do balanced into a b60. Might a balanced to rca cable combo have any impact, or is the positive effect "cancelled" somehow by the rca end?

Bill

[James Tanner]

YES THE RCA CANCELS ANY BALANCED EFFECT.  TRY FLOATING THE GROUND ON THE POWER CORD ON THE B60.

james

[cheviot100]

Piece o' cake! That fixed it completely. Thanks James.

Cheers,

Bill

[cheviot100]

....in fact I should elaborte. The sound improvement is like cleaning your glasses for the first time. This fix is astonishing and all the more so when you get it from James Tanner within a few hours of my query. He's now my nominee for the Order of Canada. Thanks again. Bill

[brucek]

This fix is astonishing

It's also quite dangerous if you've simply lifted the third safety prong on the power cord using a cheater plug.

Many Bryston amplifiers have an integral ground lift circuit that raises the potential between safety ground and signal ground without breaking the connection of the case to ensure safety. If that's the situation with the B60, then it's fine, but I don't believe the B60 has a ground lift circuit.

If you've used a cheater plug, it effectively eliminates the third prong on the AC plug.

The third prong is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. This safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault. 

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

There are other, safer methods of removing a ground loop hum.

brucek

[James Tanner]

Piece o' cake! That fixed it completely. Thanks James.

Cheers,

Bill

Great - at least now we know it is a ground loop ---I will check with engineering as to possible solutions.

james

[Wayner]

This fix is astonishing

It's also quite dangerous if you've simply lifted the third safety prong on the power cord using a cheater plug.

Many Bryston amplifiers have an integral ground lift circuit that raises the potential between safety ground and signal ground without breaking the connection of the case to ensure safety. If that's the situation with the B60, then it's fine, but I don't believe the B60 has a ground lift circuit.

If you've used a cheater plug, it effectively eliminates the third prong on the AC plug.

The third prong is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. This safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault. 

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

There are other, safer methods of removing a ground loop hum.

brucek

This is a little blown out of proportion. Unless the equipment is located on wet concrete and considering that on most equipment, the hot goes right into a fuse, there is little chance of danger, unless someone has been inside the unit, DIY'ing it, and not knowing what they are doing, or it has somehow been damaged. Lots of appliances come with only a 2 prong plug. Lots of hifi equipment comes with a 2 prong plug. I have a new metal toaster that does. Please remember, that for there to be current flow, there must be a completed circuit. Your body should not be part of that circuit, but electrical designers (good ones) have designed many safety features into a product to prevent the vary scenario you are afraid of.

Besides, the amp is still grounded to the mains via the interconnect shield. The problem was that there were too many paths for the ground and one leg had a different voltage potential then the other and when that happens, hum happens.

Wayner 

[werd]

This fix is astonishing

It's also quite dangerous if you've simply lifted the third safety prong on the power cord using a cheater plug.

Many Bryston amplifiers have an integral ground lift circuit that raises the potential between safety ground and signal ground without breaking the connection of the case to ensure safety. If that's the situation with the B60, then it's fine, but I don't believe the B60 has a ground lift circuit.

If you've used a cheater plug, it effectively eliminates the third prong on the AC plug.

The third prong is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. This safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault. 

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

There are other, safer methods of removing a ground loop hum.

brucek

Hello

All you need is one piece to be grounded (most amps are) to prevent electrocution like you are talking about. Lifting ground isnt dangerous unless the entire system doesnt have one ground. No ground on your gear will be more dangerous in terms of shocking and damaging your gear than  electrocution, but i am sure this is still possible.

[cheviot100]

FYI - now that I'm an expert in this.... ...I've discoverd that PS Audio has an attractive solution for those not entirely enchanted by the idea of a tacky little cheater plug:

(from their website - http://www.psaudio.com/ps/products/description/xstream-plasma?cat=cables-accessories)

Removable ground pin
One of the coolest new innovations we came up with on the xStream and Plasma Power Cables is a removable ground pin.
 
The ground pin on a power cable is there to tie the ground of the AC receptacle to your equipment.  However, in some cases, this ground pin can cause a ground loop and cause hum in audio and horizontal interference bars in video.
 
Instead of using a ?cheater plug? to disconnect the third prong, PS engineers invented a better way: a  screw in ground pin.  Normally, you would leave this alone. 
 
Should your system have a ground loop problem that is causing hum or buzz in the loudspeakers, simply unscrew the ground pin of the xStream and the buzz is gone!
 

thanks for all your input,

Bill