Bob Cordell Interview: BJT vs. MOSFET - Page 63 - diyAudio
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Old 18th January 2007, 02:14 PM   #621
AndrewT is offline AndrewT  Scotland
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Hi Gk,
how does that fit the conventional description of ClassA?

Surely a different description would be more appropriate.
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Old 18th January 2007, 02:19 PM   #622
GK is offline GK  Australia
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Quote:
Originally posted by AndrewT
Hi Gk,
how does that fit the conventional description of ClassA?

Surely a different description would be more appropriate.

Well, when discussing the individual stages of which the amplifier is composed, there are class A stages and class AB stages.
When Technics made amplifiers using this concept a couple of decades ago, their marketing guys called it "A+".
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Old 18th January 2007, 02:25 PM   #623
AndrewT is offline AndrewT  Scotland
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Hi,
Quote:
.....Technics....called it "A+"......
implying better than ClassA, when in fact (as reported by many commentators) it was at best worse than ClassA and some said the equivalent to "rubbish".
Typical of what salespersons will resort to when attempting to increase profit rather than improve the product and many of these far eastern products could do with some serious improving.
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Old 19th January 2007, 12:02 AM   #624
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The patent is #4,115,739 Sano, Hirosha, Hirota 4/18/77.

It seems to me, however that there were two versions of
the Technics Class A product - one of them was simply a
nonswitching output stage, which (interestingly) was about the
same as an amplifier I did once (see the thread "My first amplifier")

I did not take that design to market - and it was notably inferior
to the design discussed above.

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Old 20th January 2007, 03:50 AM   #625
GK is offline GK  Australia
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Quote:
Originally posted by AndrewT
Hi, implying better than ClassA, when in fact (as reported by many commentators) it was at best worse than ClassA and some said the equivalent to "rubbish".


Well gee, you have class A performance with less than half the dissipation. I'd say that's better than ordinary class A, wouldn't you? Oh wait, once upon a time someone called a Technics amp rubbish. Oh darn, I must be building a rubbish amplifier then too.
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Old 20th January 2007, 10:09 AM   #626
AndrewT is offline AndrewT  Scotland
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Hi Gk,
you have jumped to a conclusion I did not even imply and had no intention of implying.

I was referring very specifically to the Far Eastern practice of inventing classy sounding names for circuit implementations that do not necessarily improve performance. They often come up with "improvements" to try and persuade the gullible to part with their money, at far too frequent intervals, as they continue to chase profit margin to the detriment of quality. They are very good at making equipment cheaper to manufacture, but not so good at making it better in the sound quality stakes.

I never implied that your circuit or your improvements or your attitude came anywhere close to matching the big Internationals. I suspect "profit" isn't even in your DIY vocabulary.

Remember this started with Technics A+ which is NOT ClassA on which I have read a few reports.
I have not seen any reports on your amplifier.
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Old 20th January 2007, 11:52 PM   #627
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Quote:
Originally posted by AndrewT
Hi Gk,
I was referring very specifically to the Far Eastern practice of inventing classy sounding names for circuit implementations that do not necessarily improve performance.
Andrew, it is unlike you to generalise like that. Accuphase, Luxman, Denon, Yamaha, Sony, Nakamichi, Technics, Pioneer, Leben, Kondo are a few that springs to mind that are not bad by anyones standard.

Kindest regards

Nico
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Old 29th January 2007, 02:41 AM   #628
tcpip is offline tcpip  India
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Quote:
Originally posted by Bob Cordell in Nov 2006
The 10 ms safe area line on this transistor is at 2500 watts - very impressive. This would appear to be 8 times the 300-watt rating for the IRFP 240. But I don't know anything else about this transistor, for example, how big is the die, how big are the capacitances, how much does it cost, does it have a p-channel complement?
Is this the datasheet? The PDF I found is for a device which has a JVR suffix, not LVR.
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Old 29th January 2007, 07:31 PM   #629
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7 times the 10 mS power, 7 times the capacitance. Sounds
like about 7 parallel IRFP240's.

Whoops, only 3 times the DC dissipation - must be the package...

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Old 29th January 2007, 08:17 PM   #630
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Yes, that's about what it looks like to me. These may also be the kind of power MOSFETs that have the different gate structure (I forget what they are called - they were mentioned earlier in this thread) that results in performance characteristics that are not necessarily best for audio output applications.

Bob
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