[JAC_ZAR]

Why You Shouldn’t Connect a Single REL High Level to Mono Block Amps
https://relsupport.zendesk.com/hc/en-us/articles/115006045628-Why-You-Shouldn-t-Connect-a-Single-REL-High-Level-to-Mono-Block-Amps

Why Should I Use 2 RELs with Mono Block Amps
https://relsupport.zendesk.com/hc/en-us/articles/115006045688-Why-Should-I-Use-2-RELs-with-Mono-Block-Amps

[Bill_Bill]

Thanks Jac_Zar for the info., now I connected red wire to the positive (upper binding post circle in blue on the right side STA-9) and yellow wire connected to the positive (upper binding post circle in blue on the left side STA-9) and the black wire connected to the negative (the bottom binding post circle in blue on the left side STA-9), at the moment there is no hum sound.
Not sure if connect the REL to only one side of the STA-9, will there be any difference in sound, anyway will keep the mention connection for now, if there is any technical issue or caution about my connection now, please let me know, thanks a lot! 

[JAC_ZAR]

You should discuss this with REL or NuPrime in order not to damage devices

With the IDA-8 I use a different connection method
I do not connect the black wire

https://relsupport.zendesk.com/hc/en-us/categories/115000818247-How-To-Connect-My-REL

[rustydoglim]

Please, if you can't tell the difference between low level and high level in a blind test, do not, I repeat, do not use the high level method.
This is the recommendation from our engineer.

[Bill_Bill]

There is difference with high level connection, which is different kind of bass as the other member mention and the bass is very match with the speaker's low frquency. Anyway I'm using the method that you suggest before (blue circle) now. Thanks!

[rustydoglim]

Please provide a photo of your current connections. Did you connect the wire to BOTH of the speaker outputs circled in blue?

[Bill_Bill]

Please see the attached photos of my current connections, thank you so much for your help and advise!

Sta-9 Mono Right channel

Sta-9 Mono Left channel

[Bill_Bill]

Please provide a photo of your current connections. Did you connect the wire to BOTH of the speaker outputs circled in blue?

Hi, just wandering any comment? Thanks!

[rustydoglim]

You have to wait until next week for an answer. Support guy at factory got pulled to help with several rush shipments this week (it is a short week due to Taiwan holidays from Sep 30 to Oct 3).

[Bill_Bill]

Hi, any update? thanks and much appreciate!