Technics SA-C600 problem with subwoofer humming

[gonzo98]

Recently purchased and having problems with sub woofer (rel t zero 3).

Firstly, the system would turn off as soon as switched on with high level connection and black cable connected to black speaker post. Removing the ground cable resulted in loud hum from subwoofer.

I then looked on rel website where it suggested connecting an RCA cable to low level connection on sub. This does help but still there is some audible hum if not playing anything through the system.

I've also tried both connections at same time but the system still turns itself off.

Connecting the sub to my arcam solo works fine using the high level connection with just the speaker posts.

Any idea what's gone wrong?

 

[nopiano]

Just noticed you’ve had no replies. I’m afraid I’ve never used a REL sub, but my first instinct with symptoms of hum and unwanted switching off is a fault - and some protection circuit tripping in.

Is it new? If so, dealer first, then manufacturer. If secondhand, send it back unless seller can resolve.

 

[Messiah]

What are you connecting it too when you are having these issues?

 

[gonzo98]

Hi, what you say about the circuit tripping is what the guy at Peter Tyson said when I was trying to fix the hum problem. Both of the units where bought are still under warranty from them.

If a circuit is tripping somewhere and causing the Technics system to switch off, would that not be a problem with that system and not the sub woofer though?

I'm still hesitant to send one of thee back for repair as I'm not sure which one is at fault. As mentioned previously the sub woofer works fine on my previous Arcam Solo Neo.

Thanks

 

[Messiah]

Sorry, just saw what it is connected to is in the title. D’oh!

 

[gonzo98]

What are you connecting it too when you are having these issues?

It's connected via a high level connection to the speaker terminals, except for the black cable which I sealed off. I then run a regular RCA lead from the LFE output in the sub woofer to one of the RCA inputs (as advised in the REL website). This fixes the loud hum but still there is an audible hum I can hear sitting a few meters from the sub-woofer.

I've also tried connecting the black cable to the phono ground without the RCA connection to the LFE input and there was no improvement. However the hifi does not turn itself off at least.

I'm thinking of trying an RCA sub-woofer cable and connecting to the LFE inputs and seeing if that fixes the issue. If I were to remove the high level cables and leave the regular RCA lead connected to the LFE and notice there is no hum, would it be probably that using a sub-woofer cable in place of the regular RCA cable have the same effect?

 

[Al ears]

Hi, what you say about the circuit tripping is what the guy at Peter Tyson said when I was trying to fix the hum problem. Both of the units where bought are still under warranty from them.

If a circuit is tripping somewhere and causing the Technics system to switch off, would that not be a problem with that system and not the sub woofer though?

I'm still hesitant to send one of thee back for repair as I'm not sure which one is at fault. As mentioned previously the sub woofer works fine on my previous Arcam Solo Neo.

Thanks

I would assume that if the system does not trip out when used without the subwoofer then the issue is with the subwoofer.

 

[Messiah]

Is the Technics Class A/B or Class D?

If Class A/B then I think you should use the high level connection OR the LFE and not both. (Personally I would just use the LFE connection)

If it is Class D (sounds like you are connecting as if it is) then REL suggest (if using the high level input) not to connect the ground cable but to connect the subs .1 LFE connection to an UNUSED RCA connection on the technics. (If there is one free) to ground the connection. The sub output would not work as it would be ‘in use’.

 

[gonzo98]

I would assume that if the system does not trip out when used without the subwoofer then the issue is with the subwoofer.

That does sound logical. If the hifi is not sensing that the signal is grounded then that's probably why it's switching off. Maybe my old Arcam system does not have the same protection which is why it stays on.

It's a bit strange though that the Technics system stays on when grounding using the two other options mentioned.

Thanks

 

[gonzo98]

Is the Technics Class A/B or Class D?

If Class A/B then I think you should use the high level connection OR the LFE and not both. (Personally I would just use the LFE connection)

If it is Class D (sounds like you are connecting as if it is) then REL suggest (if using the high level input) not to connect the ground cable but to connect the subs .1 LFE connection to an UNUSED RCA connection on the technics. (If there is one free) to ground the connection. The sub output would not work as it would be ‘in use’.

It's described as a "fully digital amplifier". I'm not sure what that means. This is what one of the product descriptions I found online states:

"AMPLIFIER REQUIREMENTS:

These recommendations can only be used as a guide. Over-driving the loudspeakers risks damaging the drive units

Class A/B @ 8 Ohm Per Channel:

50W to 100W

Class A @ 8 Ohm Per Channel:

12W to 25W

Class D @ 8 Ohm Per Channel:

30W to 60W"

As you say, I have it connected as if it were class D. I think will try the LFE connection, as you suggest, before sending back for repair as I hate sending electrical items by post.

Thanks for your advise

 

[Messiah]

Pretty sure something with the way you have connected it is not right as opposed to a fault.

I would certainly just keep it simple and use the subwoofer out into the low level input. 😊

 

[landco]

My advice would be simpler - don't use REL subwoofers. Never. There are often problems with them.