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Old 31st December 2008, 12:45 PM   #91
Marc Vi is offline Marc Vi  Netherlands
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Default a wonderfull sziklai

Thank you Stefano fot publishing "The Ultimate Suplifier" in your website (see post 83).

Who will take the challenge to use my output configuration (see figure 1 in the explanation of the Ultimate Suplifier) in the V3 circuit (see post 75)?? The only thing you have to change for a higher supply voltage, is to raise R39/R40 to 56 ohm. Because 2 transistors are added (Q13 and Q14) the Vbias must be higher which can be achieved by lowering R29 in the V3 circuit to 0 ohm. Of course the output "from the neg. amplifier" must be connected to the ground.

A sziklai pair sometimes tends to oscillate. Therefor the output resistors may not be wired but must be of carbon. 5 resistors of 1,2 ohm and 1 resistor of 2,7 ohm parallel gives 0,22 ohm.

If, by the reason of the overall neg. feedback, there is still some oscillation, try capacitors parallel to R39 and R40 with a - 3 dB point above lets say 200 kHz. This will be (for R39/49 = 56 ohm) 15 nF each.

Andrew, which schematic dou you refer to? If you mean the attached file, then I agree this is a potentionally thermal instabel output. The emittor of Q111 should be connected to the emittor of Q114 and the emittor of Q112 to the emittor of Q113. Then you have to match Q114 with Q116 and Q113 with Q115 otherwise there is a change of thermal runaway of Q116 and Q115.

Marc.
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Old 31st December 2008, 12:54 PM   #92
catalin is offline catalin  Romania
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v1 tend to oscilate (1mhz) on different pcb.
By lowering the module of the function transfer (pole and zero,470p+330ohms),the v3 is more more stable and i couldn't make to oscilate.The pulse signal,amp reserve phase is better on v3.Dinamics also with the beta helper.
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Old 31st December 2008, 01:08 PM   #93
Stee is offline Stee  Italy
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Default Andrew don't need emitter resistors

http://www.esafono.it/AudioPowerAmplifier.pdf
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Old 31st December 2008, 01:18 PM   #94
AndrewT is offline AndrewT  Scotland
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Stee,
note that tr6 & 8 are connected to the outputs and that the outputs are singletons.
Your's is completely different.
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Old 31st December 2008, 05:18 PM   #95
Stee is offline Stee  Italy
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Default sorry

I have generate some confusing...
try again to convert in CFP output a "normal " amp:

http://www.mcmelectronics.com/conten...ts/50-6272.pdf


need just two resistors 120R
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Old 31st December 2008, 08:02 PM   #96
m2003br is offline m2003br  Brazil
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nakamichi PA-7 is a Nelson Pass project. Threshold "Stasis" is the about the same.
Sakis: naka PA-7 service manual states 40mA idle for each transistor, 200mA total. It is not a class AB?
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Old 1st January 2009, 02:20 PM   #97
Stee is offline Stee  Italy
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Default I have a dream

Hybrid CFP with mosfet driver 1A
exactly the same of the original BJT
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Old 4th January 2009, 06:20 PM   #98
Stee is offline Stee  Italy
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Default future of amplification

hCFP
next days i have time to test
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Old 4th January 2009, 06:49 PM   #99
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Stee you might find reversing the mosfet and bipolar to be of greater benefit.
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Old 5th January 2009, 04:30 AM   #100
Stee is offline Stee  Italy
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Default New Frontiers

http://www.ampslab.com/bi70mk2.htm
as FET on input
now
is time to lighten the load on VAS
with Mos Drivers
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