On 28 Mar 2006 23:53:14 -0800, "Andre Jute" wrote:
Ruud Broens wrote:
"Stewart Pinkerton" wrote in message
...
: On Tue, 28 Mar 2006 08:59:43 GMT, Patrick Turner
: wrote:
:
:
:
: Arny Krueger wrote:
:
: "Patrick Turner" wrote in message
:
:
: They are only as linear as a triode with regard to
: voltage gain when external loops of NFB have been applied,
: as in the case of the emitter follower connection or
: having a few BJTs with a loop of NFB around the
: lot of them to correct all their mistakes.
:
: BJTs are inherently non linear for voltage gain and MUST
: rely on large amounts of externally connected loops of
: NFB.
:
: Simply not true. Local feedback works well with BJTs.
:
: Local loops are externally applied loops of NFB.
:
: Bjts are so damned non linear with regard to voltage gain that large amount of
: NFB, local or otherwises must be applied
: to linearize the outcome, as well as raise input impedance.
:
: Some BJTs are more linear than say a 300B. Why do you keep ignoring
: this *fact*. Heresy?
:
: It isn't ludicous to drag people screaming back to the basics.
: The basic fact is that bjts WITHOUT ANY NFB, LOCAL OR OTHERWISE applied
anywhere
: have hopelessly poor
: voltage gain linearity.
:
: Utter bunk, check the spec sheet for the 2SA1216. Gain linearity is
: flat as a pancake at elevated junction temperatures, as would be
: experienced in a Class A amplifier.
yep, checking, i found it he
http://users.otenet.gr/~athsam/database.htm
the third graph shows Vbe - Ic, the _run hot_ curve
does 0.8 V Vbe @ 6 A, 400 mVtt giving 6 Att with 1.6 % distortion
certainly impressive. but, now realize the curves are taken at a
constant Vce=4V - not very realistic, is it ?
now, Hfe about 100, at this 24W class A idle point,
60 mA of base current is required. oops, at 10 A, Hfe has
gone south to only 60, creating an additional few dozens
of THD %.
2nd take:
0.6Vbe, 2.2 A idle now Hfe stays flat with 200 mVtt in, 4Att out,
distortion is 7 % or so that's indeed quite an achievement
but considering it's taken at constant Vce
reality will be worse
: Statements have been made on the group that what i am saying is untrue.
:
: That's because it is - see above.
hm, about 12 W / 8 Ohm available, 7 % THD, 8.8 W idle with the 2SA1216
you're saying there are no tubes that can beat that ?
hmmm
the truth,
Rudy
Sheesh, Rudy, this BJT the silicon clowns want to flog you isn't much
chop; in fact it appears to be just a "modern" device number assigned
to the same old silicon excrement I rejected forty years ago.
Thanks for once again demonstrating your ignorance of electronics.
A modern
300B amp, designed with high voltage, high current and high bias in the
modern Jute style has *less* distortion at full power, and practically
no 3rd harmonic distortion.
Rudy has his numbers mixed up, especially once you figure local
degeneration into the equation, to match stage gains.
I show the results of a challenge to me by
another incompetent pair of idiots. "BobC" Chernofsky and Michael
LeFevre of Magnequest Transformers. Note that even an incompetently
designed 300B such as the Bubbaland 300Bis still a more attractive
(lower odd harmonics) amplifying device than the sliver of silicon ****
this street-seller of crisped porkfat is trying to palm off on you.
Table reads right in Courier 10 pt.
Bob C's "Bubbaland" Andre's "Hedonist"
Grid Plate Grid Plate
Voltage Current (mA) Voltage Current (mA)
0.0 102 0.0 136
-22.3 87 -23.4 119
-76.0 50 -80.0 80
-129.7 18 -136.6 44
-152.0 6 -160.0 30
Load Resistance 5,000 Load Resistance 5,000
Supply Voltage 350 Supply Voltage 390
Plate Dissipation 17.5 Plate Dissipation 31.2
Power Output 5.9 Power Output 7.0
% 2nd Harmonic 4.13 % 2nd Harmonic 2.83
% 3rd Harmonic 0.82 % 3rd Harmonic 0.03
(Table courtesy of John Byrns)
******
Of course, while a silicon amp might be designed to use with
incompently insensitive speakers and will thus *require* all its power,
a tube amp like those above (including the now apparently--by
comparison to the silicon PinkoStinko is trying to flog--not quite so
incompetent Chernofsky/LeFevre noise generator), is created as part of
a chain designed back from highly sensitive speakers (both the above
amps were designed for use with Lowther horns).
Shame that those speakers sound like **** on anything with an extended
frequency range................
Thus the normal mode of
the transistor might be flat out while the 300B will idle on
milliwatts, with vanishing distortion; that is why this class of tube
amp is normally specified at the 1W it will never in normal working
see, and the transistor device at full chat.
Actually, the modern SS amp will happily deliver 500 watts of power at
less than 0.1% THD, and distortion at low levels vanishes well beneath
the (lower than that of a SET) noise floor. Shame that your flea-power
SETs are not capable of driving proper loudspeakers with a genuinely
flat response across the entire audio band.
Please also note that most top-class modern speakers are around
90dB/W/m, a mere 10dB below Jute's beloved Lowthers, so the power
required is only ten times greater. Puts those flea-powered SETs which
are utterly incompetent above 5 watts into perspective....
Especially since the first watt of a decent SS amp is still cleaner
than the first watt of a SET.
Doesn't seem to be anything left to say, does there? (Unless one wants
to gloat, and we'd never do that, would we?)
Well, you couldn't, could you? :-)
Hell, our legislators managed to criminalize fox hunting and smoking; I
wonder when they will get off their collective fat arse and criminalize
negative feedback. It is clearly consumed only by undesirables.
Since you are clearly the most deranged sociopath to stalk the audio
newsgroups since the late unlamented Alan Derrida, you're hardly in a
position to judge such matters.
--
Stewart Pinkerton | Music is Art - Audio is Engineering