Compact Sized LME49810/11 +ThermalTrak Amp - diyAudio
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Old 17th October 2009, 10:47 PM   #1
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Default Compact Sized LME49810/11 +ThermalTrak Amp

Hi everyone,

This is my new 49810/49811 + ThermalTrak Amp intended for low output power (Class-AB/B, <= 60 W). Output stage is driver + emitter follower. I have not put the heatsink for LME and driver (too noisy to do metal work in the midnight).
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Last edited by panson_hk; 17th October 2009 at 10:54 PM.
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Old 19th October 2009, 03:40 AM   #2
klewis is offline klewis  United States
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Panson,

I got both my Leach bais configuration and Cordell bais configuration for thermal trak working. The Cordell is tweaked a bit from his diagram - I decided to simulate both schemes to see how they react to temperature.
The values shown were adjusted to 2.93v at 27deg c. Then I changed the simulation temperature to 68deg c and ran it again. You can see that the Cordell version stays closer to the baseline Vbe which assumes that the Vbe transistor has a perfect thermal connection to the output transistors.

Ken
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File Type: gif leach-vs-cordell-Bias-graph.gif (9.5 KB, 4910 views)
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Old 19th October 2009, 09:56 AM   #3
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Quote:
Originally Posted by klewis View Post
Panson,

I got both my Leach bais configuration and Cordell bais configuration for thermal trak working. The Cordell is tweaked a bit from his diagram - I decided to simulate both schemes to see how they react to temperature.
The values shown were adjusted to 2.93v at 27deg c. Then I changed the simulation temperature to 68deg c and ran it again. You can see that the Cordell version stays closer to the baseline Vbe which assumes that the Vbe transistor has a perfect thermal connection to the output transistors.

Ken
Hi Ken,

Nice work! Have you tested the bias control in real circuit?
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Old 19th October 2009, 03:02 PM   #4
klewis is offline klewis  United States
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Quote:
Originally Posted by panson_hk View Post
Hi Ken,

Nice work! Have you tested the bias control in real circuit?
Panson,

Yes, using your modular approach, I now have three boards, the LME49811, with DC Servo, a board for the bias resistors, and the output board which contains the VBE transistor, predrivers, drivers and Thermal trak output devices. I put jumpers at the T Trak so that I can use either two, three or four of them in series. I had to make some mods to the driver board to go from the Leach bias scheme to the Cordell scheme. The photo shows the Cordell scheme. Note that I had to put pairs or resistors in series to get the correct resistance. Seems you never have the right stuff on hand regardless of biweekly DigiKey and Mouser orders...

My shop computer with the highend sound card died, so, no THD tests for a few weeks. But, played it with both bais schemes and it sounds great, also, sine and square waves look smooth and clean on the scope.

Ken
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Old 28th October 2009, 05:11 AM   #5
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The amp is in operation. I am going to put them in a case.
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Old 3rd November 2009, 01:31 PM   #6
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Default Playing Santana CD

One set of compact amp is setting in the lab for daily use. It is now playing Santana YouTube - PansonAudio's Channel

The operating voltage is +/- 35 V. The speaker is NHT SuperTwo (http://www.stereophile.com/floorloudspeakers/1099nht/).

Last edited by panson_hk; 3rd November 2009 at 01:35 PM.
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Old 3rd November 2009, 03:05 PM   #7
klewis is offline klewis  United States
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Quote:
Originally Posted by panson_hk View Post
One set of compact amp is setting in the lab for daily use. It is now playing Santana YouTube - PansonAudio's Channel

The operating voltage is +/- 35 V. The speaker is NHT SuperTwo (Stereophile: NHT SuperTwo loudspeaker).
Panson,

Nice little video, made me smile. I also looked at the cross over distortion video. I presume that you are showing the bais trimming out the distortion. Is this measured just with the scope? Or how do you set up for this measurement?

Thanks

Ken
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Old 3rd November 2009, 11:48 PM   #8
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Quote:
Originally Posted by klewis View Post
Panson,

Nice little video, made me smile. I also looked at the cross over distortion video. I presume that you are showing the bais trimming out the distortion. Is this measured just with the scope? Or how do you set up for this measurement?

Thanks

Ken
Ken,

Yes, it is. The cross-over waveform is the THD residual from the AP output (after the notch filter).

Panson
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Old 4th November 2009, 12:15 AM   #9
klewis is offline klewis  United States
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Quote:
Originally Posted by panson_hk View Post
Ken,

Yes, it is. The cross-over waveform is the THD residual from the AP output (after the notch filter).

Panson
Well, I guess I won't be doing that anytime soon...
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Old 4th November 2009, 12:20 AM   #10
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Quote:
Originally Posted by panson_hk View Post
Ken,

Yes, it is. The cross-over waveform is the THD residual from the AP output (after the notch filter).

Panson
What is the bias current to get the optimum result ?
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