SPA1000 and DTA-2.1BT2 hum - speaker out to rca in

[timC]

I have a DTA-2.1BT2 and I wanted a little more power for the sub. I had an older SPA1000 laying around and figured why not. The only problem is that I get a nasty hum from the sub when the DTA-2.1BT2 is turned off. I used a bare speaker wire to male RCA converter that I found on Amazon. I also have tried a pre-assembled shielded cable (male Banana to male RCA). In either case, I still get the hum. I have isolated the SPA1000 from the DTA by plugging them into separate circuits and there's still a hum. I've isolated everything else and put the SPA1000 in the place of my HT amps and I don't have a hum. The hum is in the subwoofer speaker out of the DTA to the RCA in on the SPA. So, I've heard I can remove the ground spade from one or both of the plugs or try to ground the DTA amp or SPA amp by connecting a wire from one of the chassis screws to the screw on the plate of the outlet. Any advice would be greatly appreciated.

[billfitzmaurice]

Hum is usually caused by a ground loop, ground loops are caused by having more than one pathway to ground with unbalanced interconnects. The usual fix is to disconnect the shield at one end of the interconnect. However, you should not be using a speaker level output to a power amp.

[timC]

Hey Bill
Thanks for the reply. I’m not using the speaker level output to power the amp…I’m just trying to get the audio signal from the source (Bluetooth via the specific sub out channel on the DTA) to the external amp (SPA) then use the SPA amp to power the sub. I was going with the same premise of tapping into the speaker wires on the back of head units of car stereos that don’t have dedicated sub outs. In those cases, I used cheap line level outs. In this case, the DTA has a dedicated sub out channel and I do not have a line level conversion but just a bare speaker wire to rca converter. If it’s not obvious, I’m not nearly educated enough to fully understand your answer, but I thought there may be a simple fix by potentially closing the ground loop by either removing the ground from the 3 prong plugs of one or both of the amps or by grounding the BTA to the center screw of the outlet. Again, I realize I’m showing my lack of knowledge. Just trying to Keep It Simple, Stupid…for my own sake.

[djg]

The only subwoofer out on the DTA is speaker connections to power a passive subwoofer, not subwoofer amp. Your setup won't work.

[billfitzmaurice]

Never remove the 3rd prong. It serves a vital purpose, keeping you alive. This explains causes and cures of ground loop hum: https://www.ranecommercial.com/legacy/note110.html

[dynamo]

(Double post)

[dynamo]

You need a line out converter between the powered sub output of the DTA and the RCA in of the spa1000.

Dont remove grounds.

[timC]

Thanks all. Cheap passive LOC worked perfectly.