[Dick Pierce[_2_]]

Audio Empire wrote:
On Tue, 3 Apr 2012 19:05:30 -0700, Dick Pierce wrote
(in article ):
the early ones (1967-1971) were biased so far into class "B" that they
exhibited a very apparent crossover notch distortion.

To be technically accurate, Class B operation is not a region
or continuum, it is a very specific bias point where the
conduction angle is exactly 180 degrees. Pushing it further
than that is not "so far into class B", it's into class
C operation.

To be fair, I think that most of us know that.

I don't know that "most of us know that," and, unless
you've done the survey, I suspect that you don't either.

If past posts in this and other newsgroups over the years
is any indication, then there is in fact, a significant
portion of the high-end audio readership that does NOT
know that. It is to them, as one audience, that my reply
was directed.

Further, your statement "biased so far into class 'B'"
seems to imply the assumption that class B is not a
boundary, but a region. Let's take the same grammar but
in a slightly different context:

"I never did understand was why my friend drove so far
into the border between the USA and Canada that he exhibited
a very apparent 'eh' at the end of each sentence, eh?"

Unless the asumption is the border between the USA and
Canada is a region and not a line, it;s really difficult
to imagine driving "so far into the border." He's either
in the USA, or he's in Canada, or has one set of wheels in
one and the other.

The issue of technical accuracy is important, not to the
"most of us that know," but to the many that don't. I don't
know how many myths and half-truths take on a life of their
own when bystanders to a technical discussion see terminology
bandied about willy-nilly by "most of us that know," with the
assumption that, well, "most of us know."

Actually, in the high-end world, there are those that would
say most forcefully, that "most of us know" that cables make
enormous differences, that "most of us know" that digital
can't possibly capture analog waveforms because of stuff
'missing between the samples," that "most of us know" that the
output of a CD player MUST look like a staircase, that "most
of us know" a whole nunch of things that simply aren't so.

You might assume, reasonably or otherwise, that "most of us
know" something. I, on the other hand, don't think it's
necessarily either a good idea or of service to those, even
if it's but a single person, who aren't "most of us."

And, by the way, which "us" are you talking about?

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

[Arny Krueger[_4_]]

"Audio Empire" wrote in message
...

The Citation 12 was a later generation device, which enhanced the Lin
circuit by upgrading to a differential input stage.

But, IIRC, it still used a pair of complementary drivers and NPN outputs,

Yes, it had a quasi-complementary output stage, just like the *good* Dyna
120s and just about every other SS amp of the day.

Full complementary output transistor sets with enough power handling
capacity to be interesting came in the mid-1970s.

As nice and symmetrical as these devices made schematic diagrams appear,
they provided no audible or reliability benefits.

like the ST120 (seemed to me that they were still 2N3055s, but I could be
misremembering here, I haven't laid eyes on that amp for 35 years).

The originional ST-120 schematics showed 2N3055s, but the *good* ST-120s
used the later and beefier 2N3443 devices.

Please see figure 5 at
http://cygnus.ipal.org/mirror/www.pa...s/citation.pdf

Thanks. Yes, I see what they did. Q6 and Q7 have the number 40636 next to
them. Is that an H-K part number? Doesn't sound like any transistor number
with which I'm familiar.

40636 looks to me like a RCA part designation. An early member of this
product line was the 40411 AKA "411" which was, no surprise a beefier
2N3055.

http://alltransistors.com/transistor...ansistor=20869


RCA was an early leader in producing extra-beefy NPN power transistors, but
they did not have a lot to offer in corresponding full complementary pairs.
Motorola took over, with parts like the MJE150xx series.

http://www.diyaudio.com/forums/solid...ansistors.html