Humming - help needed - a/v receiver into integrated

[entrails]

I recently treated myself to my first "grown-up" amplifier, a creek evolution 2. One of the reasons I purchased that model was for the direct a/v setting as space considerations meant I wanted to connect it to my Marantz sr5003 a/v receiver pre-outs to play the front l and r through the same speakers. The evolution sounds great with cd and vinyl but when I turn over to a/v direct a low hum can be heard though those two speakers but not through the rest of the 5.1 speakers. The hum sounds very much like the sounds I have heard from turtables before earthing and wonder if something similar is going on. I have moved the leads connecting the two amps around in case they were too near a power cord without any change. I also plugged the creek into the same mains purifier as the marantz with no change either. Does the marantz need earthing? The creek has an earthing connector at the back I assume for turntables. The marantz has an fm connection which mentions earthing but I'm not sure if thats relevant. Can anyone explain or make suggestions? It would be much appreciated.

 

[CustomCable]

I had the EXACT same problem recently with my AV receiver running into a preamplifier. The trouble is that on the AV Direct input there is effectively maximum volume. What I had to do is change inputs then set the volume to half way on the pre and then re balance the AV system. The problem is that when the gate is fully open on the pre it added alot of noise. I can actually hear the hum on any input when not playing anything through it and turn the volume pot up to about 1-130 on the dial, the hum gets very audible. Another thing that I was going to try was a Supra Hum buster but in the end I can live with my preamp at 12 O'Clock on the dial.

 

[roger06]

Interesting. I too have this problem using a Yamaha RXV1065 AV amp's pre outs into a the AV imputs of a Naim Nait 5i. I too wondered if it was down to earthing...

 

[matengawhat]

yep me to - onkyo 876 into MF A5 Pre amp - if i turn to av direct with onk in standby really loud buzz when turn on onk buzz gets considerably quieter - never managed to solve it and very annoying

 

[entrails]

These are really interesting comments indicating that this isn't to do with earthing despite the similar sound. Prior to this query I did a search on the net and initally disregarded a posting on an australian website about someone with an a/v setup going into an integrated which had incredibly loud hum. The info he got was that the make of receiver he had had very weak strength output from the preouts and was advised to buy a different make of a/v receiver. The fact that clearly not everyone with an a/v into integrated gets the hum makes me wonder is this something to do with matching strength of a/v output to the integrated? I may well have a go later with the advice to not use the direct a/v route in and rebalance but I did hope that I could keep things relatively simple for family use.

 

[roger06]

It's got worse for me after recently adding a Humax PVR.

My sub hums aswell, but I think it's 'cos it's old...

 

[roger06]

Changing the Chord Crimson for a much cheaper QED interconnect significantly lowers the hum (almost inaudible, but it's still there). I've read on other forums that the Chord Crimson causes hum when used from AV pre-outs to an integrated...

 

[pwiles1968]

I had a similar issue with my Marantz SR6003 feeding my Audiolab CDQ, the Audiolab HT setting has a Gain offset in it to volume match which I Had set to +12dB I turned it back down to 0 and it was much better.

You may not have a setting but I was wondering if it was worth buying some in line cable attenuators? Search for Rothwell Attenuators you will see what I mean, they are fairly expensive not sure if there are alternatives.

The problem is you really need a chance to wind up th volume of the AV out as much as possible otherwise the signal to noise is quite high. It will mean re balancing the speakers but that should not be too hard, just make sure you have enough adjustment available in the stereo pair, don't forget you can your centre and surrounds down to match the fronts.

 

[margetti]

Interesting thread - I too have the same problem with my Onkyo into my integrated, although it is not so bad that it worries me too much (other than the nagging annoyance that everythign is 'not quite right'). The problem only surfaced with my current integrated that I got 3 or 4 months ago - my previous one didn't have the same problem. Or rather, I think the issue did exist, but was very negligible ie only detectable with ear right next to the speaker, volume past 3 o'clock.

I have some goldenjacks attenuators (cheaper alternative to the Rothwells) that I used to use with my cdp and previous integrated - will give them a try later this afternoon or tomorrow and see what effect they have... if I can find them!

 

[entrails]

I have a pair of rothwell attenuators so had a go with them a few weeks ago, it didn't seem to make any difference. I also tried the earlier suggestion of going through the non direct route of the integrated and resetting but the hum remained the same. I've kind of become resigned to the hum staying I might give Creek some feedback about this but it seems to be a non specific a/v problem.

 

[margetti]

Just tried the attenuators - once the AV pre-out levels had been adjusted, as per entrails experience they made no difference whatsoever...

 

[pwiles1968]

That is a shame thought attenuators might help..

Is the noise there when the source is muted? Are the units plugged in to different mains rings or extent ion blocks?

 

[Anonymous]

This thread seems to have tailed off but I've just bought my first av receiver (ONKYO) and having similar issues. Strange thing is, when I put it onto "pure audio" the buzzing dissappears. Not sure if this offers any potential clues.

 

[entrails]

Hi anomie I'm still living with this problem. I did contact creek and there general feedback suggested a ground loop as most likely. I've found similar issues on threads to do with power amps and subwoofers . Not many useful suggestions so far which would work and not risk death by electrocution! Many thanks for your feedback but I think something else may be going on in mine, as I do use pure audio when playing sacds from my s370 and the hum still present on the front speakers.

 

[entrails]

Thought I would give an update on this problem. I lived with the slight hum for a long time then all of a sudden the hum became really loud stopping me from using the creek as a power amp. I did contact Creek and initially they were quite sceptical that the evo might have a fault suspecting a ground loop in my house electrics was responsible. Eventually my local hifi dealer Peter Tysons were ok about me bringing some of my kit in to see if the problem occurred there too. I hadn't bought the Creek from there but I have been a good customer there but it was really good of them. We found that the problem occurred in their show room too but when the evo was replaced with one of Tysons demo creek amps with the a/v connection there was no hum at all. After this Creek arranged for a repair job to be organised and paid for the repairs which was great as the Creek by that point was well out of warrantee. The Creek has now been repaired and there is no hum at all. The repair summary was "repaired earth tab on phono in sockets for direct av". I guess the learning point from this experience is that if you are finding that a ground loop type hum doesn't get any better with the standard trials of disconnecting possible responsible connected equipment that the next step is checking the internals of the equipment involved for faults.

 

[iMark]

I had ground loop problems when I first directly connected a computer to my stereo receiver. I had a coax cable for FM radio and the TV was also connected to the stereo.

I solved the problem by putting in ground loop insulators in both the TV and FM aerial cables. They looked like these:

http://www.amazon.de/Hama-00042997-42997-Mantelstromfilter-Koax/dp/B00006JA5N

IMHO this type of filter is one of the easiest and cheapest ways to get rid of ground loop hum from aerial cables.