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wrote:
Rich Koerner wrote in message ...
Specifically, where does using this expression, "Bias Current" point your nose.
No where, specifically!!!!!!!!!!!!!!!
Actually Rich, if this were true, we'd be a lot better off with such
an expression. Bias current points us in a half-vast way toward AB2
(or higher) operation, where grids are driven positive & grid current
is drawn, which might be partly characterized as bias current in a
folksy, audiophile kind of way.
I had actually thought of Ip = bias current, but then, looking back, he had this line in
there.
By bias currents, I do mean the idle currents in the electrodes
Why didn't he stay consistant by saying, the following.
"By bias currents, I do mean the *Bias* currents in the electrodes".
I'd still prefer something like,....
Eg1 = -52 bias voltage, Ig1 = zero IDLE current, or Ig2 = 5 ma. IDLE current.
Or, with B+ being 400 volts, for -52 volts of grid bias on G1, this yields zero grid
current on G1, and 5 ma. for G2, etc....
But, that's just me.
IMHO the most silly thing about this
is that it is irrelevant to the original subject and to 99% of all
tube amp concerns on these 2 NG's. AB2 is not used for low-distortion
hi-fi, nor for the normal economically efficient guitar amp. It is
primarily a modulator or old tube PA amp thing. The usual AB2 ckt
requires low-distortion triodes in A driving the finals' grids through
a driver xfmr. AB2 takes a lot of driving power compared to our usual
AB1 because a lot of it is wasted in grid dissipation when the grids
are driven positive, and this is also why a xfmr is usually needed to
handle the driver current, and why it is impossible with the types of
PI ckts we see in most guitar amps, which clip (poop out the driving
signal) when the grid gets up to zero (or thereabouts). I'm sure you
seen this on your scope a thousand times.
The whole deal of class increase is really simple: it is all about
ways for increasing the drive to the tube, to produce more power
without exceeding its dissipation rating, while accepting higher
distortion and other construction issues as a tradeoff. It is the
tube's fixed dissipation rating that drives all of these strategies,
mostly the plate dissipation but the screen as well, sort of like
finding ways to pile up more amps in your shop without raising the
ceiling (plate) or breaking the window (screen). By the time it gets
to C with tubes, we are done with audio because it's gone nonlinear
and its dit-dah or whatever for RF.
LOL, what a trip!!!!!!!!
The life of free electrons in motion is an interesting thing.
Amazing have to can get then march to your commands on a vacuum tube.
I guess there are the many who are very limited in marching tunes.
OK boys, let's all get in formation, and march to the A class tune!!!!!!!
Hey boss, can we learn the new AB1 tune the LOUDER bands are playing!!!!!!!
We're pooped out, and tired of *wasting energy* with all this marching stuff.
Can't we just sit on chairs, and play the new LOUD AB1 tune!!!!!!!!!!!!!!!
You can still be the boss, and direct the music!!!!!
Damn, I've got to get some sleep!!!!!
Have you ever seen or worked on an AB2 guitar amp, Rich?
RONFLMFAO!!!!!!!!!!!!!!!!!!!!
Only when there is a short from G1 to B+ from the beer inside the
amp!!!!!!!!!!!!!!!!!!!!!!
There may or
may not be one out there in the high-pwr catagory, wld make sense.
Hmmmmmmmmmmmm.................!!!!!!!!!!!!!
Maybe one of those WWII Kw tube amps with the tranny's and big bottles were that way.
Only seen one of them in my life when I was in an electronics surplus place when I was in
high school.
Beyond this, the notion that an amp may behave like lower class
because of what it signal may or may not do, is also poppycock. If an
AB1 signal is conducting on both halves for 360 degress at a low
setting, in no way does that make this a "class A mode." Even if it
has not had any cutoff yet, the tube's dissipation is rising, vs real
A mode which is not.
There you go!!!!!!!
I caught that, but from the other direction. Either way, it takes ya to the same place.
The AC and DC characteristics don't line up to meet the definition.
But, I didn't feel like getting into it, after a long day.
LOL, like now.
This heads, not completes, the list of
stiffnecked sins involved in such thinking or terminology, and is why
I got so stiff in my long earlier post, in light of the persistent use
of such poppycock by pompous nincompoops passing it off as
knowledgegrin.
I guess you can understand why I loose it in here sometimes.
No sleep, and intellectual idiocy!!!!!!!!
Bad combination!!!!!!
Remember Steely Dan's "Reelin' In the Years"?
Damn, that reminded me, I have to call Elliott.
Hey DUDE, I LOVE YA!!!!!
I never rolled on the floor Laughing so hard!!!!!
I also know you have chops more than most, from your post.
And, you get the handle on the juice squeezer.
You, I'm sure, having touched upon the basics of what is needed in a 400-PS, and would
have no problem figuring out how that rascal does it's thing.
Yeah, having understanding of dynamic drive, the loading for such, and the effects of
same, escapes most.
BTW, it was fun having the audio high brow stop in with their road show.
Maybe, I should stick my nose in there from time to time, and check it out.
Hey, what the hell, right.
wink
Thanks for the laughs.
You're cool!!!!!
BTW, what do ya play, if I may ask.
Regards,
Rich Koerner,
Time Electronics.
http://www.timeelect.com
Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
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