Rel T7i and Stellar S300

I spent quite a bit of time searching existing threads this prior to posting.
I was hoping someone could help me get to the bottom of my T7I hum issue. I have reviewed the available documentation from REL and videos as it relates to connecting and troubleshooting and have had no success with the reccommended steps so far.

Sub seems to perform perfectly when amp is powered on. I immediatly get a hum when amp is powered off (this is typical I understand).

Sub is connected to + L&R on amp. I initially tried to float the ground. before noticing the hum after powering off

Tried connecting ground to the outer ring of an unused S300 RCA jack to establish ground (no luck) There is no grounding post available on the back of this amp

I then tried running an RCA from the LFE.1 on the sub to an available jack on the amp (no luck)

I then disconnected everything from the sub accept AC plug and switched on. Still Humming. I then tried the same in other areas of my house which I know are on different electrical circuits. Still the same. Should this thing hum when not connected to any signal? It is a real hassle to have to switch the sub on and off every time I use the system and frankly not worth the compromise.
The issue I am having sounds very similar to the REL/BHK problem that is resolved with the resistor network

I have not been able to reach Rel support over the phone as they are probably affected by the CA covid shutdown. My frustration is leading me toward returning it for a SVS SB1000 which has speaker level connections and a standby mode. I would appreciate any suggestions to try before I box up the REL and ship it back. It would be a shame. Thanks.

I have the same problem. I just leave my amp on all of the time. I hope you fine a solution.

Kindest Regards,

If you’re using high-level, have you tried jumping from the terminals on the speakers themselves? (Supposedly REL says this is an ok connection method.)

I’m not using the high-level connection, so take it with a grain of salt.

Otherwise, test the AC ground?

I’m using RCA’s on my T/5i’s, and I also had hum. Upon advice from Music Direct, I disconnected the AC ground from the amp. Against my better judgment initially, but I did that and no issues (or hum) since. (You can use a cheater plug, or just cut the ground off the power cable. If it’s not an expensive power cable, that is!)

Might be worth a test.

Just tried the cheater plug. Same issue. I appreciate the help though.

I’m pretty surprised running the RCA from an unused one on the amp didn’t work. Seems to work for most. I usually ever hear this from S300 folks, but it’s possibly just like BHK amp connection when it needs the resistor network from REL. I really hope they’re doing alright and are able to open soon. I’ve worked with them in the past and they’re a great group of people!

So strange that you’re getting hum when disconnected from all signals. I was getting hum when connected to RCA. But when I disconnected the RCA, hum was gone. (I didn’t need to disconnect ground when disconnected from signal. it was the signal cable that was causing the ground loop.)

looks like I will just have to leave the amp on and keep the sub. Seems to be an acceptable practice. BTW, James you recently sold me my S300 and I want to thank you for the exceptional service and follow up emails. Great sounding unit. As a new customer I can now understand why the Hi-Fi community holds PS Audio is such high regard.



It’s better for the sound if you leave any Class D amp like the S300 on all the time but the REL should not be humming on it’s own with nothing connected. That’s an indication that there is an internal grounding issue with it’s amp that you are correcting by connecting it to the S300 and turning them on. You are completing an open ground circuit. When you turn the S300 off the circuit is open again. If you bought the REL new you should return it as defective and get a replacement.

If you don’t want to send the sub back or leave the amp on you can use one of these to create a solution using the grounding outlet on the front of the unit where the white plastic plug is.


I am waiting to hear back from REL via email. I hope they will replace it if indeed there is a problem with the amp. It arrived in perfect condition direct from rel. I guess it is just bad luck. Anyone have a direct contact there? It has been difficult communicating over support tickets as they asked for my serial number several days ago and I have not heard back.

I apologize, most of my contact with them has been over phone. Hopefully they get back soon.

I realize quite some time has passed but I thought I would provide some information I recieved after speaking with REL support. It may help some others experiencing this issue. This hum will affect all T Series rel subs connected to Stellar Amps. It is not ground loop or anything like that. It is simply inherent in the design of the components and use of the speakon connnector. There is no way to avoid this Hum issue. I was offered 2 solutions by REL.

  1. Leave the amp on all the time. (my current solution)

  2. Buy a WiFi enabled plug so i can turn on the sub without using the switch on the rear.

Leaving the amp on has worked out fine and I really like the unit. It is just something worth noting if people want to use that combo. I sort of though this would be common knowledge by now with so many Stellars and RELs out there.