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Old 21st August 2005, 08:40 AM   #11
routhun is offline routhun  United States
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Hi CBS240,

Sorry for the confusion that I caused. I am not sure whether I can post a copy righted schematic on this forum, but I want to mod this amp, that's why I didn't say it is the schematic of my harman kardon receiver in my first post. But after lot of questions about the design I need to reveal its source.

Thanks,
Nageswar
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Old 21st August 2005, 08:40 AM   #12
routhun is offline routhun  United States
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Hi Chris,

The Nikko receiver was given to me by somebody with left channel out. I replaced the outputs with MJL4281A and MJL4302A complementary pair. After replacing the outputs sometimes outputs on that channel is used to get very hot. After some more checking I found that capacitor in the output Zobel network is open. I replaced that and it is working fine from then.
Bass is really tight from this receiver. I really like the sound. The real good part in this receiver is its tuner section.

Regarding AVR-520 receiver, the preamp of this receiver contains lot of opamp buffer sections with lot of compensating capacitors and mute transistors in the signal path. With all this heavy handed signal processing I think quality was deeply buried in the preamp itself. I am thinking of repeating my test with Nikko preamp and Harman's power amp section and I'll post the result.

Thanks,
Nageswar
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Old 21st August 2005, 02:30 PM   #13
anatech is offline anatech  Canada
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Hi Nageswar,
That should be an interesting experiment. Later Nikko's did not sound very good sadly.
Do you have a schematic for the NR-1019? I may be called upon to repair my friends unit any time now. It is very old and I've cleaned the switches once for him.
-Chris
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Old 21st August 2005, 09:30 PM   #14
routhun is offline routhun  United States
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Hi Chris,

I don't have the full schematic of the Nikko receiver, but I hand traced the schematic of the power amp section. If you want that, I can scan and mail it to you.

Thanks,
Nageswara
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Old 21st August 2005, 09:47 PM   #15
anatech is offline anatech  Canada
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Hi Nageswar,
That's very kind, thank you! If I come across the manual I'll get you the full schematic. Send it to bhome at sympatico dot ca. My profile link works too.
-Chris
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Old 24th August 2005, 10:00 PM   #16
K-amps is offline K-amps  United States
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Some good suggestions here, I'd lose the lytic in the input after the 330R, replace with a metalized poly, or PIO.
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Old 25th August 2005, 08:47 PM   #17
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Default I have been studying amplifiers for decades (4) and i could not see nothing that can

Produce the sound you are perceiving.

Well, lets see if i will have time enougth to learn more, because this is showing me that i need to construct more, listen more to have more experienced looking schematics.

Sorry my question.... had you compare them only with power amplifiers operating....no pr amplifier, filter or processors in the chain?.... sorry, i really think you made your tests with a power in separated mode.

Those small transistors in parallel are to face the power needed in that stage, dividing power and using the hi gain characteristic of those transistors...one single hi power unit will loss in gain.

I could not find nothing to replace...nothing to change, and my imagination showed me a nice sounding amplifier.

regards,

Carlos
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Old 11th September 2005, 05:39 PM   #18
routhun is offline routhun  United States
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Hi Carlos,

You are right, this is a nice sounding amplifier. I've built a preamplifier using an opAmp and bypassed the pre-amp in this receiver. It sounded very well. So I went on searching for an used preamplifier for this receiver. Finally I got hold of Yamaha C-4 preamplifier. The sound from this Yamaha C-4 and Harman Kardon AVR-520 combination is phenomenal. Guys if you want a discrete line amplifer, discrete class A headphone amplifier, and an optional two band parametric equalizer - look no further all these qualities are in Yamaha C-4. Its a fully discrete preamplifer with matched JFETs in input stage. It transformed my audio experience.

Thanks,
Nageswar
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