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sgobowinski
2012-04-27, 22:13
Hi there - been a user for a while now, however I have just made some connection changes to my system, which consists of a SBT-->Coax-->DAC-->Preamp-->Power amp. When I turned it on, there is a loud ground hum through the speakers when selecting the DAC as the input.

This hum goes away immediately if I turn the SBT power supply off, however it does not change anything if the SBT is actually on or off itslelf. That is, it appears to be coming from the power supply of the SBT.

I've tried another power supply (from another SB Classic I own) and it is exactly the same.

No connection changes or component changes have been made - that is, this scenario was fine before all of this.

Any chance I can find the cause of this?

Joe_M
2012-04-28, 06:58
Is any of your equipment connected to a device that is connected to cable tv or satellite (e.g. TV, cable box)?

If so, try disconnecting the cable tv and/or satellite coax and see if the hum goes away. If that's the cause you can buy a ground loop isolator that will usually cure the problem.

Also, if the equipment is plugged into different electrical outlets, that can cause a ground loop if the outlets are on different circuits.

garym
2012-04-28, 07:01
Hi there - been a user for a while now, however I have just made some connection changes to my system, which consists of a SBT-->Coax-->DAC-->Preamp-->Power amp. When I turned it on, there is a loud ground hum through the speakers when selecting the DAC as the input.

This hum goes away immediately if I turn the SBT power supply off, however it does not change anything if the SBT is actually on or off itslelf. That is, it appears to be coming from the power supply of the SBT.

I've tried another power supply (from another SB Classic I own) and it is exactly the same.

No connection changes or component changes have been made - that is, this scenario was fine before all of this.

Any chance I can find the cause of this?

I'm a bit confused as you say you "have just made some connection changes to my system" at the beginning and then "No connection changes or component changes have been made" at the end. What did you change? Do you mean you simply disconnected cables then reconnected exact same cables?

sgobowinski
2012-04-28, 16:49
I'm a bit confused as you say you "have just made some connection changes to my system" at the beginning and then "No connection changes or component changes have been made" at the end. What did you change? Do you mean you simply disconnected cables then reconnected exact same cables?

SORRY. I realised this was ambiguous. What I meant was that I pulled apart the system and put it back together in exactly the same way. That is, I re-cabled the system, but I didn't change any components or cabling........sorry for the confusion.

This is so strange - no, there is no video equipment connected.

garym
2012-04-28, 17:23
Odd. I'm assuming same exact electrical outlets.

Joe_M
2012-04-29, 13:10
Try reversing how the SBT's power supply is plugged into the outlet. Sometimes switching the plug polarity will get rid of a ground loop.

If that doesn't work, try using an optical cable between the SBT and the DAC instead of coax.

If your DAC doesn't have optical input, you could get an optical to coax converter like this one...

http://www.amazon.com/Cables-Go-40019-Optical-Converter/dp/B0002GV876

However, If you use an optical/coax converter there is the risk that the power supply for the converter will also cause a ground loop.

Wirrunna
2012-04-29, 22:41
SORRY. I realised this was ambiguous. What I meant was that I pulled apart the system and put it back together in exactly the same way. That is, I re-cabled the system, but I didn't change any components or cabling........sorry for the confusion.
...consists of a SBT-->Coax-->DAC-->Preamp-->Power amp.
This is so strange - no, there is no video equipment connected.

If an RCA plug is not in properly (outer ground making contact) it can have the reported effect, have you tried re-plugging each of the cables?

Mnyb
2012-04-29, 22:50
Is the Touch wired or wifi ?

If wired do not use shielded cat6 cable use unshielded.

sgobowinski
2012-04-30, 03:40
If an RCA plug is not in properly (outer ground making contact) it can have the reported effect, have you tried re-plugging each of the cables?

Resolved: This fixed the issue. Not sure how it occurred in the first place though. Maybe there is a loose contact in one of my RCAs going from the DAC to preamp? I have swapped the RCA for my SACD player with the one on the DAC (same brand/type) and I'll see how everything goes.

Thanks all for a great forum and fantastic support (as usual).