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Old 11th July 2011, 07:33 PM   #21
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Default triple territory.

I have just a tad of ringing on my triple (not simmed). So you might want to simulate and leave your real world design open to a few stability enhancements.

Besides the pre/driver RC decoupling Cordell advises on , here are a few additional "tricks".

The B/C driver stopper caps are from the APT1 and the parallel L/R network is a Harmon Kardon "trick"... both reduce the VHF bandwidth of the stage without any degradation. The HK L/R works similar to the main OP inductor typical of most amps. Both mitigate negative resistances at the OP bases , augmenting the basestoppers action.

PS - make your own "L/R" by wrapping 20-25 turns of thin wire around a 100R 1/2w resistor.

OS
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File Type: gif triple tricks.gif (55.2 KB, 1130 views)
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Last edited by ostripper; 11th July 2011 at 07:36 PM.
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Old 11th July 2011, 08:42 PM   #22
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Quote:
Originally Posted by ostripper View Post
I have just a tad of ringing on my triple (not simmed). So you might want to simulate and leave your real world design open to a few stability enhancements.

Besides the pre/driver RC decoupling Cordell advises on , here are a few additional "tricks".

The B/C driver stopper caps are from the APT1 and the parallel L/R network is a Harmon Kardon "trick"... both reduce the VHF bandwidth of the stage without any degradation. The HK L/R works similar to the main OP inductor typical of most amps. Both mitigate negative resistances at the OP bases , augmenting the basestoppers action.

PS - make your own "L/R" by wrapping 20-25 turns of thin wire around a 100R 1/2w resistor.

OS
Thanks OS I'll try that.
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Old 19th July 2011, 09:06 AM   #23
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With small changes in TMC is possible to get below ppm at 20kHz and 80W/6R.
Input 0.12v 20kHz
1W/6R Total Harmonic Distortion: 0.000026%

Input 1V 20kHz
80W/6R Total Harmonic Distortion: 0.000093%

Diagrams in this order:
schematic, FFT 1W, FFT 80W, OLG and CLG

Someone can ask why I use local VAS feedback R15//C22. Whitout it disstortion is even lower, but the phase is passing dengerously close to 180 degree, and with this arrangement it is much smoother.
dado
Attached Images
File Type: jpg DADO-TT-TMC-3-1_015-triple-fina2.sch.jpg (145.8 KB, 1103 views)
File Type: jpg 1W.jpg (210.3 KB, 993 views)
File Type: jpg 80W-6R.jpg (228.4 KB, 822 views)
File Type: jpg DADO-TT-TMC-3-1_015-triple-fina-OLG.jpg (373.9 KB, 764 views)
File Type: jpg DADO-TT-TMC-3-1_015-triple-fina-CLG.jpg (363.8 KB, 119 views)
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Old 19th October 2011, 02:25 PM   #24
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Finally I am going to test this amp.
Last simulation are here and this is going to be the schematic I will use for real life test.
Some simulated data are here:

THD20k at 100W//8ohm is 0.72ppm
THD20k at 1W//8ohm is 0.11ppm

Slew rate with input filter 150V/uS
Slew rate without input filter 280V/uS

FFT atached are:
40W 1kHz
1W 20kHZ
1W 1kHz
dado
Attached Images
File Type: jpg shcematic.jpg (156.6 KB, 457 views)
File Type: jpg 100W-8ohm-20kHz.jpg (200.9 KB, 425 views)
File Type: jpg 1W-8ohm-20kHz.jpg (211.2 KB, 152 views)
File Type: jpg Square-wave.jpg (170.0 KB, 141 views)
File Type: jpg FFT-40W-1kHz.jpg (166.7 KB, 182 views)
File Type: jpg FFT-1W-20kHz.jpg (155.4 KB, 138 views)
File Type: jpg FFT-1W-1kHz.jpg (171.7 KB, 111 views)
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Old 27th October 2011, 08:14 AM   #25
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Finilly I've powered my amp. I did bias adjustment and then noticed that output jumps when I touch drivers heathsink. Adding 220pF between base and collector of the drivers cured that(probably some oscilation). After that I did some measurement with sinus and square wave signals using 8ohm load. All looked OK. A power supply was temporary one with ordinary diode bridge and 2x4700uF.
I was curious to hear it and I connected it to my listening setup, one PCB only.
First impression was very good, crystal clear hights and phenomenal bass.
I will present more measurings and listenings soon.
dado
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Old 27th October 2011, 08:42 AM   #26
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Thumbs up congratulations

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Old 12th November 2011, 11:09 AM   #27
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I've got idea to make universal PCB which I can use for more then one configuration of this amp. In this case it can be high Feedback amp, and low Feedback amp.
In this forum there are some discutions about high Feedback with very low THD, and low Feedback and higher THD but with more "benign" harmonics distribution.
Here is the PCB and simulation of two low Feedback amps, one with NJF LTP and other with BJT LTP. I think I am going to make one of both type, listen and hope to hear the differences.
dado
P.S. Important feature of the low Feedback amp is better phase and gain margin.
Attached Images
File Type: jpg DADO-TT-TMC-5.LAY].jpg (295.9 KB, 411 views)
File Type: jpg WideOLG-NJF-LTP.jpg (195.7 KB, 444 views)
File Type: jpg WideOLG-BJT-LTP.jpg (193.4 KB, 191 views)
File Type: jpg WideOLG-NJF-LTP-OLGgraph.jpg (386.4 KB, 139 views)
File Type: jpg WideOLG-BJT-LTP-OLGgraph.jpg (390.2 KB, 71 views)
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Old 22nd December 2011, 04:54 PM   #28
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Default Dilemma

After listening to the triple and problem to stabilize it I am not sure if a triple is worth a hassle. I simulated here a triple and standard EF OPS.
IPS is the same for both amps, with NFET cascoded LTP, VAS is emitter follower before and emitter follower as buffer after VAS transistor and TMC is used. Global Negative Feedback is the same for both.
What you think looking at FFT for both of them? Distortion of the triple is lower but it is so low for both of them and I think no one could hear difference. Standard EF shows dominant second harmonics mostly.
dado
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File Type: jpg dilemma.jpg (260.0 KB, 164 views)
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Old 22nd December 2011, 06:30 PM   #29
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Quote:
Originally Posted by dadod View Post
After listening to the triple and problem to stabilize it I am not sure if a triple is worth a hassle.
dado
Hi Dadod,

Try this amplifier SYMEF amplifier . No problem with stability. Triples work.

kind regards,

Harrison.
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Old 22nd December 2011, 06:46 PM   #30
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Quote:
Originally Posted by OnAudio View Post
Hi Dadod,

Try this amplifier SYMEF amplifier . No problem with stability. Triples work.

kind regards,

Harrison.
Yes I know it works, my worked too, read the whole thread. The question is does it give so much benefit, if we can get similar result with simpler circuit.
dado
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