Noise

•Make sure all connections to the active speakers are good.

•Make sure none of the signal cables are routed near

AC cables, power transformers, or other EMI-inducing devices.

•Is there a light dimmer or other SCR-based device on the same AC circuit as the SRM350v2? Use an AC line filter or plug the SRM350v2 into a different AC circuit.

•Disconnect any cables which come in from outside, such as cable TV, satellite TV or roof top antennas. They must be disconnected from every part of your system, such as the TV, VCR and preamp. If the hum goes away, you can add a “ground loop isolator” in your cable line. This is an inexpensive device available from video or TV dealers, or you can make your own from two TV baluns (standard TV 75/300 ohm adaptors):

Hum

•Turn the LEVEL control all the way down. If the noise disappears, it’s coming from the signal source. If not, try disconnecting the cable connected to the INPUT jack. If the noise disappears, it could be a “ground loop,” rather than a problem with the SRM350v2. Try some of the following troubleshooting ideas:

•Use balanced connections throughout your system for the best noise rejection.

•Whenever possible, plug all the audio equipment’s linecords into outlets which share a common ground (see the diagram on page 13). The distance between the outlets and the common ground should be as short as possible.

Never remove the ground pin on the power cord of the SRM350v2 or any other component. This is very dangerous.

•The hum may appear when using an unbalanced source (consumer preamp, CD player, VCR, etc.). This is caused by the unbalanced-to-balanced interface between the devices (and exacerbated by the fact that most consumer audio equipment have a two-wire linecord, without the third-pin safety ground).

Use an interconnect cable wired as shown below. The important point is that the shield and the wire from the XLR pin 3 are joined at the RCA (source) end.

RCA

3-Conductor Cable

XLR

 

 

 

 

 

2

1

 

 

 

3

shield

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Balun

join (+insulate)

Balun

 

The baluns are threaded at one end (75 ohm) to fit TV coax cable and have two wires at the other end (300 ohm). They will not affect the video quality.

•If the hum persists, try removing components one at a time from the back of the mixer or preamplifier, and check for hum each time (turn off your equipment before you undo any connections). It is fairly common to find more than one problem.

•If your preamp or mixer are the only things connected to the SRM350v2s and the hum is still there, try different connection cables, or move the preamp/mixer to another location.

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