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Class D Switching Power Amplifiers and Power D/A conversion

Building Connex NXP amp
Building Connex NXP amp
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Old 25th January 2010, 01:16 PM   #1
Kjeldsen is offline Kjeldsen  Denmark
diyAudio Member
Join Date: Dec 2003
Location: Randers, Denmark
Default Building Connex NXP amp

I'm building a connex NXD 8950th amp, and would like som good advice on the layout. Im using two modules (4 channels all together) and two transformers.

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As I see it I can have trafo's apart, or I can have the two NXP modules apart. Or the third solution, I can make two seperate amplifiers. What I'm looking for is the best soultion in order to avoid hum/hiss in these class D modules.

The black thing is the heatsink, that will also be the top of the amplifier.

Last edited by Kjeldsen; 25th January 2010 at 01:45 PM.
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Old 8th April 2010, 08:04 AM   #2
Kjeldsen is offline Kjeldsen  Denmark
diyAudio Member
Join Date: Dec 2003
Location: Randers, Denmark
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I have some minor noise issues on this amp, but hopefully they will dissapear in my first revision. The noise/distortion is very low, and do not follow the volume settings, so at normal listening levels it's not audible.

The amps is almost dead quite, when no signal is appliede. I have had two other class D amps. A CAD audio D400S and a Panasonic SA-XR50. This amp does sound different from those other D amps. The Panny sounds best on digital input, but I have used it for an active 2 way system with analog input. The CAD audio was very powerfull, and had a special sound. It was very dry and tight at the bottom end, and vocal stood out in a funny way. It's hard to describe but the closest I can get is, that the vocal sounded like it was still in the recording box at the studio. Every one who have heard their own voice in a very damped box/room knows what I'm talking about.

The Panasonic have real good bottom end and highs on spdif input, but lacks in the analog input. The bottom end is a bit loose and top end blurred. The amp should never be stressed, because it will then sound harsh.

The Connex NXP TDA8950th based class D module is very different from the CAD audio. The bottom end is fullbodied and yet tight. The top end is also very good and the harshness others have reported is not something I hear. But, I do use 4" Tangband paperfiber cones, so this might be an issue. If I can get rid of the noise/distortion I think these amps will stay in my system for a long time. I also have a MiniAMP from MiniDSP. These amps might take over for the 4" tangbands and the the NXP's for the bottom.

Last edited by Kjeldsen; 8th April 2010 at 08:07 AM.
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