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Old 10th July 2012, 08:01 AM   #1
mesc is offline mesc  Norway
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Question nxv300 build

Hello I have a problem with newly built aussieamp. These are the the old nxv300 modules, they have been laying around for some time. I'm using buffalo32s as source (with volume controller). The problem is that when I hook up the buffalo (either rca or xlr) I get some sort of buzz in the speakers. And even stranger, with the volume all down, I still get music through the speakers. The buffalo I've used before and never had any problem. The buffalo is not grounded.

Last edited by mesc; 17th March 2013 at 02:58 PM. Reason: wrong icon
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Old 10th July 2012, 08:54 AM   #2
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Quote:
Originally Posted by mesc View Post
Hello I have a problem with newly built aussieamp. These are the the old nxv300 modules, they have been laying around for some time. I'm using buffalo32s as source (with volume controller). The problem is that when I hook up the buffalo (either rca or xlr) I get some sort of buzz in the speakers. And even stranger, with the volume all down, I still get music through the speakers. The buffalo I've used before and never had any problem. The buffalo is not grounded.
Hi Mesc

Do you have the nxV300 power supply grounded to mains chassis earth?

cheers

Anthony
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Old 10th July 2012, 09:05 AM   #3
mesc is offline mesc  Norway
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Yes I have. I have been experimenting some more, and, this is what I found. I tried different sources. Sound card rca out: This one also produces significant buzz when connected. Tested the buffalo on some headpones, it seems the volume issue remains there as well. So I guess somehow the buffalo has changed, probably something I've done with the configuration. Now I'm playing music with a small mp3 player as source, and a homebuilt cmoy as preamp. There is some buzz with that one too, but less than the other options.
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Old 10th July 2012, 09:21 AM   #4
mesc is offline mesc  Norway
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Here's a picture. mains earth is connected to chassis right where it enters. I've seen this recommended as far as I remember. But will there be loop problem with these two seperate connections?

Also I should mention, with the current setup the sound is more of whoosh now than buzz. (with the cmoy peamp)

Edit: Oh yes. underneath the nxv300 is a peaker protect board. Ive soldered speak-pos underneath the board
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Last edited by mesc; 10th July 2012 at 09:25 AM.
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Old 10th July 2012, 11:17 AM   #5
mesc is offline mesc  Norway
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Ok if we disregard everything but the whoosh now. Because I think maybe the buzz might be some computer noise.

When the amp is not connected to any source, there is whoosh. When connected to the cmoy there is whoosh with slight buzz..

So I guess the problem to focus on is idle whoosh noise in my amp. Of course I would like it to be as silent as possible. So, Im looking to solve this somehow. I know its possible to have silent nxv300, I just want to know what I might have done wrong.
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Old 10th July 2012, 01:31 PM   #6
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From your photo it looks like you have connected to chassis via the loudspeaker
GND return is that correct?
If so it would be best to undo this and wire it directly to the loudspeaker
terminal. Ideally the power supply Power ground should be connected to
the mains earth right at the point on the chassis where mains Earth is connected to the Chassis earth point.
This way you are not relying on the chassis case to provide an earth return to the mains chassis earth connection point.

With the input shorted do you get any noise coming from the loudspeaker?
If so at what distance can you hear this sound?

Cheers

Anthony
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Old 10th July 2012, 01:58 PM   #7
mesc is offline mesc  Norway
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With the input shorted there seems to be no change in idle "whoosh". The "whoosh" is low, I must have the ear very close to the tweeter.

I will do as you suggest with the speaker return.
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Old 10th July 2012, 06:01 PM   #8
mesc is offline mesc  Norway
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I have rearranged the grounding, except the main earth connection which still is by itself on the other end.
There is no difference. Maybe its normal, I'm not sure, but its not my idea of dead silent.

About the grounding as seen in the picture, is it ok to have it like that, or shouldn't it be like that regardless?
It was kind of easier/tidier like that.
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Old 10th July 2012, 11:48 PM   #9
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The woosh sound I assume is actually hiss, a small amount coming
from the tweeter with your ear up to it is quite normal for this amplifier.

You could leave the grounding arrangement, what you may need to do is to
connect a ground wire from the Cmoy pre-amp GND point to the power amplifier power GND, this should help with the buzzing noise and will equalise the GNDs between the to units, rather than it trying to happen through the signal GND.
The same can be done between the Computer case and Power amp mains GND point.

Anthony
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Old 17th March 2013, 03:19 PM   #10
mesc is offline mesc  Norway
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Hello again

This project has been in stasis for some time now. I now have a nice opportunity to finish.
I have done some improvements in wiring (making it safer), and also played some music, and I like it very much.
When using my battery powered Objective2 as pre with small mp3 player as source, there is no unusual hiss. I'm confident its normal and I'm happy

But... there is that issue with grounding of source or pre, and it creates problems. I suppose its a typical green diy'ers problem. Ground loop something.

Your last post mentions making connections between the other appliances, but wouldn't that be the same as a typical grounded electronic equipment, except maybe the ground goes into the wall and everywhere?

Also, it sound strange to me to have a separate wire going between my hifi equipment, never seen that before :P

Hopefully I can learn to tame this ground hog once and for all.

-steoll
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