REL Subwoofer and S300

Is anyone using the S300 with a Rel subwoofer using the high level inputs?

It’s balanced right so just connect the red and yellow cables and leave the black floating.

Fine when the s300 is on but in standby I get hum and also when the s300 is powered off.

I tried grounding the black to a chassis screw on the top and also the phone cable trick but no joy, still the same.

What are others doing to kill the hum?

I had this with my REL sub. Just connect an RCA cable between an unused port on the back of the S300 and the .1/LFE port on the sub. That eliminated the hum for me and is what REL recommends in their manual.

Thanks. So are you just using the RCA inputs on the s300 and a cable directly to the .1?

This I have tried and I still get the hum. I’ll try again tomorrow as it’s late here now but I didn’t get any joy.

maybe consider the Jensen Iso Transformer?

not really expensive, but, Wow…

Yeah, that’s exactly what I’ve done. Just used one of the leads from an old RCA cable and went from the S300 to the .1/LFE on the sub. Also, per REL, I made sure the .1/LFE level was set to zero (knob turned all the way down).


Getting absolutely no joy with this. Seems there is no grounding when the s300 goes into standby or off.

Is this usual?

Add an extension piece of wire to the REL grounding wire and ground it something else in the equipment chain besides the S300. When I used Class D amps I connected the wire to a grounding lug on the line conditioner. It is also going to make a difference as to whether the amp in the REL is a Class D amp itself or A/B.