# REL Subwoofer and S300 **URL:** \ **Category:** Audio Components\ **Created:** [January 12, 2020, 8:48pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805 "2020-01-12T20:48:50Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![DaveH](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@DaveH](https://forum.psaudio.com/u/DaveH)\ **Post date:** [January 12, 2020, 8:48pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/1 "2020-01-12T20:48:50Z")
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? ---
**Author:** ![trey0thompson](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@trey0thompson](https://forum.psaudio.com/u/trey0thompson)\ **Post date:** [January 12, 2020, 9:38pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/2 "2020-01-12T21:38:15Z")
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. ---
**Author:** ![DaveH](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@DaveH](https://forum.psaudio.com/u/DaveH)\ **Post date:** [January 12, 2020, 10:14pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/3 "2020-01-12T22:14:24Z")
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. ---
**Author:** ![iron](https://sea1.discourse-cdn.com/flex015/user_avatar/forum.psaudio.com/iron/32/31006_2.png) [@iron](https://forum.psaudio.com/u/iron)\ **Post date:** [January 12, 2020, 11:04pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/4 "2020-01-12T23:04:10Z")
maybe consider the Jensen Iso Transformer? > **[SP-2SX.pdf](https://www.jensen-transformers.com/wp-content/uploads/2014/07/SP-2SX.pdf)** > > 467.50 KB not really expensive, but, Wow… ---
**Author:** ![trey0thompson](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@trey0thompson](https://forum.psaudio.com/u/trey0thompson)\ **Post date:** [January 13, 2020, 12:40pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/5 "2020-01-13T12:40:25Z")
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). ---
**Author:** ![DaveH](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@DaveH](https://forum.psaudio.com/u/DaveH)\ **Post date:** [January 13, 2020, 6:04pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/6 "2020-01-13T18:04:43Z")
Thanks. Getting absolutely no joy with this. Seems there is no grounding when the s300 goes into standby or off. Is this usual? ---
**Author:** ![dawkinsj](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@dawkinsj](https://forum.psaudio.com/u/dawkinsj)\ **Post date:** [January 13, 2020, 7:21pm UTC](https://forum.psaudio.com/t/rel-subwoofer-and-s300/14805/7 "2020-01-13T19:21:09Z")
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.