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#222448 - 09/24/08 05:58 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: Jc]
SolidState Offline
veteran

Registered: 11/08/06
Posts: 124
Thanks so much for all the support guys. Such a fantastic Axiom community we have. With regards to the hum issues... In testing this afternoon I found that by populating each module with two speakers and not one (the system is 5.1) the hum went away!! In other words using an EVEN number of speakers with the A1400-8 seems to remove the hum. I discovered this by connecting just LR first no hum... connect LR SR SL hum... add center... no hum... use center LR and one rear... no hum... add rear again for 5.1 hum.... added a rear center for 5.1 ES and again no hum. It seems to me the hum is introduced when I am using an uneven number of speakers and one of the modules is only driving one speaker. I was thinking of testing again with a 8 Ohm high watt resister connect across the terminals of a module only populated with one speaker. I also confirmed the hum using just a single channel on the amp though the hum wasn't as pronounced and seemed to increase logarithmically when uneven speaker count was connected. In other words one speaker produced least hum while 5 speakers produced the most. I will get some shop speakers over to this customers house and confirm this by populating all of the channels. I have a feeling the SNR would be LEAST with all 8 channels populated and would get worse working back in even speaker counts whilst it's the opposite with uneven speaker counts where 1 speaker would have the least and 7 the worst. It's also interesting to note this is a non issue with a pre that has balanced out. I am going to run tests using my notebook with trueRTA and REW. I'll post the graphs with results using various numbers of even and uneven speaker counts... 1,3,5,7 and 2,4,6,8 . Thanks again for the responses guys!!! sure makes one feel great and is reassuring to see the designer/OEM/ODM and other end users so willing to come forward and help. It's a fantastic example of Axiom's dedication to it's customers and a great indicator of how happy other customers are that they are willing to come on here and help others out without any volition simply because they want to share with others these fantastic products.

Justin

PS By systemic I mean anyone that's using non balanced inputs... here's dreaming this customer (a relative) gets the AVP-A1HDCI as these two pieces would be a match made in heaven IMHO ;\)

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#222453 - 09/24/08 06:33 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: SolidState]
SolidState Offline
veteran

Registered: 11/08/06
Posts: 124
OK I've confirmed the uneven speaker counts were causing this hum. I will run the trueRTA measurements and post them in the coming days but I will also try the various pinout/cable arrangements suggested by JC and Tom and also post trueRTA results cross referenced and matrixed.. though I don't have the gear to measure accurately on the highend of the spectra. It looks like my uncle is gunna just have to order a rear center and a couple of Algonquins to solve this issue ;\) Lucky guy...

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#222459 - 09/24/08 07:13 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: SolidState]
EFalardeau Offline
connoisseur

Registered: 08/27/07
Posts: 3270
Loc: Laval, Quebec, Canada
You can confirm! And now it is time to turn the thanks to you!
I still a very, very light hum in a central channel (louder when my SACD player was ON, but before it had played once). I just hooked the unused channel to a dummy zone 2 cannel of my 805 and gone!

Hum... That's one for Mr. Tom! \:\)

I had actually hooked up in 6.1 before completly without hum! So it is pretty strong evidence now.

So, thanks SolidState for having done more testing (I am sort-of not confortable to play too much in the back of the A1400 as I accidentally shorted my first one moving the furniture to reach it... the spectacular firework sorts of sticks into your memory and makes you stay clear of it! \:\) So I am very happy you did it! ).
_________________________
E = MC2 = ((2M80 + VP180 + 4QS8)/(EP800 + EP500))^(ADA1500 x D2v)
Audiobytes! 2M22! 2VP150!

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#222470 - 09/24/08 10:11 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: EFalardeau]
SolidState Offline
veteran

Registered: 11/08/06
Posts: 124
Hi EFalardeau!

Hey that's great to hear!!!

Hi JC,

With regards to Tom's suggestion, and again my knowledge is limited to Heathkits and highschool electronics but I do claim to be a "pro" HT installer ;), by connecting the hot to pin 2 of the XLR and the ground to pin 3 without using pin 1 would this not result in a 6 dB loss in signal? Would this not mean I'd have to set the volume knob to double on the Denon to achieve the same SPL?

Justin

PS How would this affect "gain structure" and "headroom" ?
Also I am curious what the affective pin out is when using a TRS 1/4 mono to RCA (included adapters) with the A1400-8's combo XLR/TRS Neutrik plug?


Edited by SolidState (09/24/08 10:46 PM)

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#222520 - 09/25/08 09:59 AM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: SolidState]
ihifi Offline
local

Registered: 10/06/06
Posts: 280
Loc: CT
Justin,thank you for identifying a hum issue with the use of odd number(s) of channels using unbalanced inputs into the amp. How were you able to confirm that this is a "non issue with a pre that has balanced out"? I have 7 channels connected to the A1400-8 using balanced outputs from the prepro and can say that the background is absoultely dead quiet even when I tested by putting the volume on the prepro way up.

EFalardeau, I assume the dummy zone 2 output on your 805 had audio output? Did you not connect a speaker to that channel on the amp?

I had heard somewhere that using all eight channels would actually run the amp cooler. This hum issue with odd number(s) of unbalanced inputs is also interesting.

John
_________________________
John
Our HT


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#222521 - 09/25/08 10:04 AM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: ihifi]
EFalardeau Offline
connoisseur

Registered: 08/27/07
Posts: 3270
Loc: Laval, Quebec, Canada
I did not connect a speaker to the unused channel. The audio is life (but without actual audio signal) as I use the "zone2 power ON" as 12V trigger for the A1400.
_________________________
E = MC2 = ((2M80 + VP180 + 4QS8)/(EP800 + EP500))^(ADA1500 x D2v)
Audiobytes! 2M22! 2VP150!

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#222524 - 09/25/08 11:19 AM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: EFalardeau]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16289
Loc: Leesburg, Virginia
 Quote:
audio is life

Preach it, brother!
_________________________
"I wish I had documented more…" said nobody on their death bed, ever.

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#222534 - 09/25/08 01:09 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: pmbuko]
SolidState Offline
veteran

Registered: 11/08/06
Posts: 124
Hi ihifi,

I determined the balanced had no hum by using an Aardvark Q10 pro soundcard for audio recording as a source.

Justin

PS I found using a PC with a pro sound card as the source produced the best sound I've heard yet from the A1400-8... Amazing one can get balanced output of a caliber competing with those very expensive pre/pro

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#229173 - 11/09/08 08:30 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: SolidState]
SolidState Offline
veteran

Registered: 11/08/06
Posts: 124
 Originally Posted By: SolidState
Hi EFalardeau!

Hey that's great to hear!!!

Hi JC,

With regards to Tom's suggestion, and again my knowledge is limited to Heathkits and highschool electronics but I do claim to be a "pro" HT installer ;), by connecting the hot to pin 2 of the XLR and the ground to pin 3 without using pin 1 would this not result in a 6 dB loss in signal? Would this not mean I'd have to set the volume knob to double on the Denon to achieve the same SPL?

Justin

PS How would this affect "gain structure" and "headroom" ?
Also I am curious what the affective pin out is when using a TRS 1/4 mono to RCA (included adapters) with the A1400-8's combo XLR/TRS Neutrik plug?


This question has never been answered...

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#229181 - 11/09/08 09:01 PM Re: Axom A1400-8 amp hum from Denon AVR-4306... [Re: SolidState]
myrison Offline
connoisseur

Registered: 02/03/08
Posts: 1898
Loc: Austin, TX
Justin - Just a suggestion... If you haven't already, send JC a PM (or e-mail him directly) to make sure he saw your response and question. I don't think he monitors each thread actively like some of the other Axiom employees do, so direct contact might be more effective.

Jason
_________________________
Epic 80-800: HG Cherry | HT Pics

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