Axiom Home Page Forums General Discussion Technical Questions Active Auto On/Off on EP175

I recently purchased an EP175. For whatever reason I can't get the Active Auto On/Off feature to automatically shut the amp off after a period of time with no signal from the amp. I'm using the high level imputs, and wonder if the auto on/off feature will not work when using these. Even with the amp off for several hours, there is still a quiet humm from the amp and it is not shutting off.

Any help understanding what is wrong would be appreciated.

Thanks,

Kaz

I believe it will not work with the high level inputs, but I am not certain. Worth giving Axiom a call.

Are you using high level inputs because your receiver does not allow for using a coax sub cable?

Yes

Kaz, the use of the high level inputs should make no difference in this matter, since if there's no input there's no input, and the amp should shut off after the designed time regardless of what connection is used. You might contact Axiom directly on the possibility that the shut-off circuit on your particular EP175 isn't adjusted correctly.

Hello Kaz,

Your remark that there is a "quiet hum" present when the EP175 has not shut off suggests to me that you have a ground loop hum. The EP175 would perceive this as a signal input even if your main AV receiver or amplifier is shut off. Ground loop hum can exist even if all the other components in your system are turned off. Check the cable-TV input. It's usually the source. Disconnect it where it enters your cable/converter box. If the quiet hum disappears, then you'll need an isolating transformer available from Axiom or (rarely) from your TV cable provider.

Try our trouble-shooting steps to getting rid of the ground loop hum (in the Articles Archive) and it should solve the problem of the sub not turning off.

As JohnK pointed out, the auto circuit operation is not dependent on using the low-level or high-level inputs.

Regards,

Alan

Good one Alan! I can't believe none of us picked up on that "quiet hum"! This makes a lot more sense.

Thanks for the reply, Alan. Your suggestion makes a lot of sense, however there is one problem.....it's used for stereo only, so no TV coax cable is hooked into the amp.

The only thing I can think of is that the amp is a tube amp which I'm wondering might have something to do with it. However, I would guess that whether it's a tube amp or solid state/transistor amp, when they're off, they're off, and there would be no signal either way. Might it be possible the tube amp, even when turned off, is somehow still leaking a tiny bit of juice through the speaker outputs?

I'm at work now, but when I get home tonight I will try experiment a little by unplugging the amp completely. I'll also go check out the troubleshooting article you recommended as well.

Thanks again.

Kaz


ps. thanks to all the others for their responses also.

Kaz,

It doesn't matter if your cable isn't hooked up to your amp. Take it from me. I was in the same spot as you. I coerced the cable company to come and install an isolator at the entrance and that took care of all my problems. It has to do with the way the cable company grounds the incoming cable.

Kaz, as you described the situation, it would appear to be less likely to involve a ground loop. You say that the quiet hum is coming from the sub amp(not the driver cone). This would be more likely to indicate a mechanical hum from the sub amp transformer windings(nothing very unusual or to be concerned about as such)rather than an electrical hum caused by a ground loop, coming from the driver cone. If there was a strong enough ground loop current to keep the sub amp "awake", it'd be likely that you wouldn't be asking about a slight hum from the amp which was supposed to be off, but rather a loud hum coming from the cone when the sub was on and playing.

Ok, did a little experimenting last night. It's definitely the receiver/amp that is causing the hum and not the sub or the sub amp. As I mentioned, my receiver/amp is a tube amp, and when I unplugged it from the power source, the quiet hum on the sub stopped completely. However, with the receiver/amp still plugged into the power source, even with it turned off, the sub still hums. In other words, the receiver/amp is sending a continuous signal to the sub, which appears to the be the reason the sub is not shutting off.

I'm no electronics expert, but I guess my receiver/amp either leaks juice when turned off or it is not grounded properly.

Kaz

Are the Sub and Amp plugged into the same outlet? If not, try that.

Aaaaahhhh... that explains it.

It's not hum that you're hearing, it's warmth!

[quote=MarkSJohnsonAaaaahhhh... that explains it.

It's not hum that you're hearing, it's warmth! [/quote]
That's was really funny!

Hi kazkru,

Very good trouble-shooting on your part. Now you can try connecting a separate ground wire to a chassis screw on your tube receiver amp. Run the ground wire to a known ground if you have one (a cold water pipe?) and see if the hum disappears when you touch the ground wire to the ground, or you could try the center screw on a household AC outlet, if it's properly grounded.

An alternative would be to run the ground wire to a chassis screw on the rear panel of the subwoofer amp. That may eliminate the hum. I once had to run a separate ground wire from a big old Macintosh tube power amp chassis to the pipe underneath a basement bar installation. The reviewer/journalist (an icon on Canada's CBC radio network; for those with long memories, it was Clyde Gilmour of the network radio show, "Gilmour's Albums") was so grateful to me, he mentioned me on-air and gave the magazine which I edited at the time (Sound Canada) a nice plug.

A bit of a digression, but I mention it to illustrate the extreme measures that are sometimes necessary to get rid of hum.

Regards,

Alan