"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets - Page 131

npdot · 18th May 2012, 08:49 PM

AndrewT,

Here is clipping at 3% THDN.

Neel

AKN · 18th May 2012, 08:54 PM

ndepot,

Yes, about the same 1KHz performance as the wire (opc:s measurement). Not bad for a 30 year old design. Sub 0.1% at 300W 100kHz is impressive (I think).

I will soon build a soundcard interface. With current soundcard in loopback 3:rd harmonic dominates at -100dB so it will hardly be sufficient (measuring 3:rd) for this kind of amp. However rest of the harmonics is down at -110db, noise at -120dB so maybe I'll see someting.

I hope we will se a lot of measurements, it’s quite revealing.

npdot · 18th May 2012, 08:56 PM

The LME supply is +/- 65V from HP regulated power supplies. Owen's board has additional capacitors for isolation and noise filtering.

The transformer >1KVA

Smoothing caps are 72,000 uF for each rail, plus 1000 uF more per rail on the board.

I believe that we can rule out the transformer.

AP2 · 09:07 PM

Quote:

Originally Posted by npdot

AndrewT,

Here is clipping at 3% THDN.

Neel

Hi,
frequency of the input signal?

AndrewT · 18th May 2012, 09:00 PM

Can anyone account for the flat tops of the clipping not being at the top?

npdot · 18th May 2012, 09:04 PM

AKN,

I would like to know more about your soundcard analyzer project.

opc · 18th May 2012, 09:07 PM

I have no idea why the clipping looks like that... I've never seen that before, and my measurements here don't reflect that.

I'll test in a few minutes and report back.

It almost looks like the power supply begins to collapse at the peak and doesn't recover until the load is lightened.

I think AndrewT might be on to something asking about the supply and the transformer, but npdot's setup seems pretty hefty.

I'll post measurements in a little bit with the DPS-600

Cheers,
Owen

npdot · 18th May 2012, 09:09 PM

Andrew,

Just brainstorming:

1. Output device transconductance droop due to current surge
2. Output device transconductance droop due to rapid changes in die temperature.
3. ??

AP2 · 09:21 PM

please, change f of input signal 10x high and show clip.
if you change f eg. low (150hz) and (clip angle) moves to counter-clockwise, then is a problem on psu

npdot · 18th May 2012, 09:14 PM

AP2,

Signal is 1KHz.

18th May 2012, 08:54 PM	#1302
AKN No snake oil diyAudio Member Join Date: Aug 2005 Location: In the middle of Sweden	ndepot, Yes, about the same 1KHz performance as the wire (opc:s measurement). Not bad for a 30 year old design. Sub 0.1% at 300W 100kHz is impressive (I think). I will soon build a soundcard interface. With current soundcard in loopback 3:rd harmonic dominates at -100dB so it will hardly be sufficient (measuring 3:rd) for this kind of amp. However rest of the harmonics is down at -110db, noise at -120dB so maybe I'll see someting. I hope we will se a lot of measurements, it’s quite revealing. __________________ / Anders

18th May 2012, 09:14 PM	#1309
AP2 diyAudio Member Join Date: Dec 2009 Location: Italy	please, change f of input signal 10x high and show clip. if you change f eg. low (150hz) and (clip angle) moves to counter-clockwise, then is a problem on psu Last edited by AP2; 18th May 2012 at 09:21 PM.

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18th May 2012, 08:56 PM	#1303
npdot diyAudio Member Join Date: Dec 2009 Location: Great Falls, VA	The LME supply is +/- 65V from HP regulated power supplies. Owen's board has additional capacitors for isolation and noise filtering. The transformer >1KVA Smoothing caps are 72,000 uF for each rail, plus 1000 uF more per rail on the board. I believe that we can rule out the transformer.

18th May 2012, 09:00 PM	#1305
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Can anyone account for the flat tops of the clipping not being at the top?

18th May 2012, 09:04 PM	#1306
npdot diyAudio Member Join Date: Dec 2009 Location: Great Falls, VA	AKN, I would like to know more about your soundcard analyzer project.

18th May 2012, 09:07 PM	#1307
opc diyAudio Member Join Date: Oct 2004 Location: Ottawa, Ontario, Canada	I have no idea why the clipping looks like that... I've never seen that before, and my measurements here don't reflect that. I'll test in a few minutes and report back. It almost looks like the power supply begins to collapse at the peak and doesn't recover until the load is lightened. I think AndrewT might be on to something asking about the supply and the transformer, but npdot's setup seems pretty hefty. I'll post measurements in a little bit with the DPS-600 Cheers, Owen

18th May 2012, 09:09 PM	#1308
npdot diyAudio Member Join Date: Dec 2009 Location: Great Falls, VA	Andrew, Just brainstorming: 1. Output device transconductance droop due to current surge 2. Output device transconductance droop due to rapid changes in die temperature. 3. ??

18th May 2012, 09:14 PM	#1310
npdot diyAudio Member Join Date: Dec 2009 Location: Great Falls, VA	AP2, Signal is 1KHz.