[oz_audio_todd]

Ok, quick question here for people who hopefully know.
Oh wait, first up, it seems that I like more bass than might be considered flat to the average measuring device, so I want/need to run subs.
May be I am missing something, but my system gets used for 2 channel and AV and I dont see why I should have different levels of bass for the two, so I want to run the subs all the time.
I have Marantz receiver and rotel power amp with a cheap Jaycar plate amp and a couple of carbon fibre Jaycar 12's. Previously I was, without problem, using just the receiver amps and tapping off the pre-outs for the sub, now using the rotel power amp I am getting some very nasty and anoying humming out of my fronts  >: |
Admittedly, when I tried this, the sub plate amp and power amp were plugged into sockets on different walls, which I firstly need to try changing, but i wonder if any body else has come across this prob and/or knows how to fix or something to try?
Thanks guys, yours in audio and excessive extended bass,
Todd  : )
 

[ltr317]

It could be you're getting hum from a grounding problem in one of your outlets. 

[rabbitz]

I assume you are using the Marantz pre out L&R front to your Rotel power amp. At a guess I say the Rotel has no mains earth (2 pin only on the mains lead).

With plate amps in the mix it's a good idea to run all you gear from single power board. Even 2 powerboards from the same power point can cause a problem (very common). You can check this by removing the earth to the plate amp by cutting off the earth pin on a double adaptor and plugging into that. This is for a temporary check only to see if the hum disappears. No equipment should be run without an earth pin and once the test has been done, throw the double adaptor away.

The other possibilty is the TV screen so try disconnecting that completely (including the aerial).

If none of those work then you have to disconnect everything and start adding one component and different leads a time until you find the offender.

[Mr Content]

Hey Pete, hows things, nice to see you on the board. we must catch up soon.

Nig

[Wayner]

You only need to have one component connected to ground (and not really even that). Unless you are going to run equipment in the rain or on wet concrete, the grounding thing isn't an issue. What I do suspect is that you are connected to the mains ground in several spots.

Remember that all of the equipment becomes interfaced and connected via the interconnet's shield, which is connected to neutral and then hence, ground.

Wayner

[oz_audio_todd]

Hey guys, thanks for the replys, I will definately have to have a look at the power lead for the Rotel and try both amps on the same board as a starting point. If it turns out to be the case, is it worth trying a mains lead with an earth pin?
Not sure how the TV would/should/could affect the situation, but I will keep it in mind too.
Itr317, what might that grounding problem entail, how would I know, and how might it be fixed pls?
And yes, I have all 5 pre-outs going into the Rotel 5 channel, with the fronts also split to the sub amp.
Sorry Wayner, but what does all that mean that I have to do/try pls?  : )
Thanks again guys, hopefully tomoz I can start trying all these suggestions (except may be the double adaptor, earth pin remove thing which sounds kinda dangerous?)
Todd : )
 

[Wayner]

I'd have only one component grounded. That would be the preamp.

Wayner

[ltr317]

Hey guys, thanks for the replys, I will definately have to have a look at the power lead for the Rotel and try both amps on the same board as a starting point. If it turns out to be the case, is it worth trying a mains lead with an earth pin?
Not sure how the TV would/should/could affect the situation, but I will keep it in mind too.
Itr317, what might that grounding problem entail, how would I know, and how might it be fixed pls?
And yes, I have all 5 pre-outs going into the Rotel 5 channel, with the fronts also split to the sub amp.
Sorry Wayner, but what does all that mean that I have to do/try pls?  : )
Thanks again guys, hopefully tomoz I can start trying all these suggestions (except may be the double adaptor, earth pin remove thing which sounds kinda dangerous?)
Todd : )

A simple test to determine if you have a grounding problem is to convert your 3 prong plug to a 2 prong by using an adapter to eliminate the earth connection.

[Wayner]

That would work swell.

Wayner

[rabbitz]

Hey Pete, hows things, nice to see you on the board. we must catch up soon.

Nig

Hi Nig

Have moved onto other things such as staying alive.

Give us a call when the weather warms up a tad and we'll have a get together.

Cheers Peter

[rabbitz]

Mains grounding is very important for the safety of yourself and your family. Asian manufacturers tend to leave it off most audio and video equipment.

The best place for a mains ground is the power amp as that's usually the prime candidate for a meltdown plus handles the higher currents and voltages. When a high VA transformer melts and the primary windings go to chassis you really need a mains ground for safety. It's really necessary for correct RCD operation as they depend on the mains ground as they cannot protect against electric shock where current flows through a person from active to neutral. A circuit breaker can help here but is not fast enough to stop death. Besides I prefer not to have this voltage come back up the signal hot or ground to the pre amp, source etc.

TV sets are renowned for bad grounding schemes which can upset audio equipment and there is plenty of information on these issues (had one here recently that was effecting a FM tuner that didn't share the same aerial).

Try the single powerboard first as the odds are this is the problem (I've seen it happen so many times in installations with a sub plate amp).

[Mr Content]

Hey Pete, hows things, nice to see you on the board. we must catch up soon.

Nig

Hi Nig

Have moved onto other things such as staying alive.

Give us a call when the weather warms up a tad and we'll have a get together.

Cheers Peter

Hi Peter, sure will give you a ring soon. Good to hear you are concentrating on staying alive, still my most important endeavor too. Keep well, and will see you soon.

Nig

[Mr Content]

Sorry Todd, for the off topic chatter between Pete and my self, he's a good friend.

Nig

[rabbitz]

Look forward to it Nig.

The medical profession has been trying to do me in for the last couple of years but have failed. 

[oz_audio_todd]

Hey Nig, No sweat, i have been avoiding the circle for a few days anyway as I am embarrassed to say that I havent gotten around to moving all my gear into a position where i can try any of these suggestions yet  : (

[Mr Content]

Hey Nig, No sweat, i have been avoiding the circle for a few days anyway as I am embarrassed to say that I havent gotten around to moving all my gear into a position where i can try any of these suggestions yet  : (

Dont worry Todd, its all good here, thanks for being fine about the OT.

Nig aa

[oz_audio_todd]

OK, my bad, big time, but I finally got round to tiding up enough to pull my racks out so I could try all this stuff. I wont go into details,but after about an hour of playing with no results, I stuck me a fluke DMM on the RCA inputs of my cheap plate amp to find that I have half a volt of AC coming out of my inputs.
I cant help but thinking that this could be the cause of my problem and a big problem at that.
Can I asume that this thought is correct?   
Thanks