Is the Stellar S300 considered two "monoblock" amps for purpose of REL sub pairing?

Wonderful news!

Red and yellow to the same post then black to the chassis ground, right?

When I went to shut everything off last night, I turned off the amp first and the sub started humming again. Apparently, the amp has to be on to complete the ground for some reason, but when it is on, sub is dead quiet. Don’t know what that suggests, but it is the reason I initially thought the chassis ground idea had failed - I never turned the amp on, just heard the hum when I turned the sub on by itself. I can live with it – I’ll just have to turn the amp on first before switching on the sub. The sub does not go into standby when nothing is playing.

So, final, successful wiring configuration: Yellow to Left (+), Red to Right (+), and Black to chassis ground.

Hmmm…I have never used red to right yellow to left. They should go to the same post iirc. Mine are a different series, and I have had different amps, so you may be right for your set-up. I do have RELs though and have had them connected to PSA M1200s.

https://relsupport.zendesk.com/hc/en-us/articles/115004649048-Stereo-Subs-Connection-Method

I seem to recall some discussion elsewhere on the forum that, once connected successfully, you have to keep the S300 powered up to prevent hum from REL T series subs. Or I guess I could have imagined it. I think most (or at least many) of us with solid state amps tend to leave them on anyway, unless we’re powering down the entire system, including the sub.

Glad it worked out. Yes, I should have mentioned the S300 needs to be flipped on.
@leean We have quite a high number of people running T series subs with the M700s. You have nothing to worry about. When connected properly, they work perfectly.

@jamesh : yeah seem the hum issue can get away with that wireing config, but seem the Sub does not go standby when feeding nothing to it

SO this make me think of a order of turn on /off your entire system in case of sustaining or doing something
1/turn off sub -> 2/ turn off the power amp -> 3/ entire system
turn on system
1/ turn on the power amp -> 2/sub -> 3/rest of system
Some body can correct the order if wrong ?

I think both red and yellow in same post in one channel is for the dual sub, each of sub will work as mono sub.
i see on youtube they did that

Yes, per the manual, attaching both red & yellow to a single positive would be the correct configuration for mono block - not 2 channel.

Leean - your on/off sequence would be good – I think most importantly, sub is the last thing to be powered on, and first thing to be powered off.

Thanks to the PS folks, Leann, and everyone else who helped me work through it.

And, most importantly, now that all the set-up issues are resolved and I can focus on it – THE AMP SOUNDS GREAT !!

Awesome Dusty, enjoy!