Yamaha's Hyperbolic Conversion Amplification (HCA) Circuit - diyAudio
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Old 30th September 2009, 11:44 AM   #1
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Default Yamaha's Hyperbolic Conversion Amplification (HCA) Circuit

last weekend I have heard two different power amplifiers by direct comparsion:
1) Pass "X 600" vs.
2) Yamaha "MX 10.000" (MX10000, MX-10000)
I was surpriced about the low sonic differences between this two devices and I guess, that the HCA technology is also a good solution, especially if the loss power must be lower by the same output power.

Are there HCA diy projects respective other commercial amplifier brands, where is HCA technology inside?

Last edited by tiefbassuebertr; 4th January 2014 at 04:45 PM.
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Old 30th September 2009, 04:13 PM   #2
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Pair of Schottky non-linear resistances spanned between two offset followers
gives the following push and pull currents into the load: I've never been sure
if this behavior was Class A? or Class AB? Maybe its your Hyperbolic thing?
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Old 30th September 2009, 05:40 PM   #3
cbdb is offline cbdb  Canada
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Quote:
Originally Posted by kenpeter View Post
Pair of Schottky non-linear resistances spanned between two offset followers
gives the following push and pull currents into the load: I've never been sure
if this behavior was Class A? or Class AB? Maybe its your Hyperbolic thing?
Is there a schematic of the OPS?
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Old 30th September 2009, 06:42 PM   #4
teemuk is offline teemuk  Finland
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Damnit, MX-1000 and MX-2000 (amps with the same feature) service manuals are missing the pages that have schematics!

Anyone have these?
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Old 30th September 2009, 07:08 PM   #5
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cbdb>Is there a schematic of the OPS?

Yes.

This circuit I am about to show you is an older one, created the above plot.
Certainly not the simplest, nor best way I could have drawn for you today.

Magic is simply two independent single ended class A amplifiers, any type will do.
Offset one amplifier to track one emitter drop above the desired output voltage.
Offset the other one to track one emitter drop below the desired output voltage.
A quiescent current is set by resistors spanning the gap between these two offsets.

If that resistance is linearly resistive, then only linear class A crossing can be the
result... Power wasted at quiescent is exactly the same as at full output swing.

But if that resistance rides on the curve of a non-linear diode.... You can shape it.
The Quiescent current can be far less than full output swing. But still no transistor
is ever turning off.

This is my own circuit, nothing to do with Yamaha's. And possibly irrelevant.
We still at this point know nothing about "Hyperbolic" to guess what that means?
But the Yamaha advertised description (so far) fits how mine behaves to a tee.
Is Yamaha using the same trick, or I've spun completely off a different tangent???
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File Type: gif Fork68b.gif (63.7 KB, 2765 views)

Last edited by kenpeter; 30th September 2009 at 07:16 PM.
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Old 30th September 2009, 07:25 PM   #6
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Hi

I think that you can find both service manuals and schematics at Jan Dupontís website ACD
http://www.audio-circuit.dk/

BTW look at patent US4803441

Cheers
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Old 30th September 2009, 07:42 PM   #7
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Darn, and I thought MY way (with a big Schottky) overcomplicated.
Yamaha looks like an analog computer based upon log nonlinearity of
bipolar transistors??? How they keep that from becoming temperature
dependent? A Schottky on the other hand dissipates almost nothing
in this application compared to the capability of its TO220 package...

But I think we are talking the same end result, as far as current go.
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Old 30th September 2009, 08:28 PM   #8
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All these efforts (going all the way back to the Threshold
dynamic bias patent) exploit some non-linear function to keep
the output stage in forward bias. The presumption is that this
non-linearity is better than the one in the output stage devices.

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Old 30th September 2009, 10:25 PM   #9
mlloyd1 is offline mlloyd1  United States
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this all sounds like barry thornton's "hypersonic class a" from those old (and nice i thought SAE amps). i think he used schottkys in the output stage also.

hmmm ... maybe i shoulda kept quiet, i might be dating myself again ...

mlloyd1
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Old 30th September 2009, 11:06 PM   #10
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Its far easier to match curve of an identical two terminal diode to compliment
the same on the flip side...

Than trying to match up swervie-curvies of an NPN to PNP, especially if those
same devices are also the ones dissipating the big power... Many of the purpose
built complimentary pairs have lots of emitters with series resistance, too linear.
Just build in some error correction, and let them be as linear as they wanna be,
why fight it?

The Schottky can't drop more than .3 forward volts, so its largely out of the
power dissipation business at any realistic Class A current. But it gives back
the curves we need to achieve this A-AB-hyperbolic crossing or whatever it is...
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