Date: Mon, 02 Apr 2012 12:59:10 -0700
From: Jim Barber <audioguy@q.com>
Subject: Re: [Amps] amp cooling / triodes vs tetrodes
Leigh,
Not to drive everyone up a tree with this topic, but do you know of any
non-proprietary designs that might serve at least as a basis for a
properly-done EBS implementation?
I'm not thinking so much of modifying my (newest) commercial amp, but I
do have a YC156 project that seems to be in eternal overhaul, as well as
a Henry 3KA that could benefit from such a beast.
Along that line I also (still) have one Alpha 77 left with their EBS,
but I'm not sure I'd qualify that one as more than a good start at
"properly done", at least by today's standards. (It's from before they
added the control pot, early design)
Thanks,
Jim N7CXI
### You can buy the entire TRI-state EBS from the Ameriton catalog.
They have 1-2 versions of it. Complete, ready to go.
It might need some tweaking to obtain higher V levels for a YC-156.
## I dunno why you would want to mess with EBS....if you use VOX on SSB.
You don’t need to suck 350 ma of idle current on a YC-156. 150-200ma is plenty.
150 ma idle on a 3CX-3000A7 triode is plenty for superb imd .
150-200 ma idle on a 3CX-6000A7 is ample for good imd.
## On CW mode, there is NO reason at all to suck
150-350 ma of idle current !!!! On CW, just crank up the bias V..until the
idle current is down to 10-20ma. Use a string of series 1N5408 or 6A10
diodes
for this job.. and or... a single wire wound resistor. On CW..with any GG
triode
you can not run the idle current at zero ma...or you will get key clix. With
10-20ma
you wont get any at all. Tank eff will be improved a whole bunch too. Your
idle power
will be so low, it’s a non issue.
## EBS, even tri-state is a fubar way to go on CW..and also FM.
## EBS, if using PTT SSB is ok..and saves heat. If using VOX on ssb, the
ebs will
not buy you much for heat savings at all. The only time it kills heat is
between when you
stop talking..and when the VOX drops out. The EBS is NOT gonna be fast enough
to toggle
between syllables !
## If you want to see something really stupid, check out the 3 x hole
tetrodes from QRO, etc.
They idle at a whopping 750ma ! The 2 x holer idles at 450 ma (225 ma per
tube)
Using the 3 holer with the same plate xfmr as the 2 holer is even more silly.
If any
sb-220 etc, sucked 750ma, it would burst into flames.
## sure the small tetrodes can be driven with 10-20 watts. Who cares. The
typ xcvr puts out
100-250w these days. You run a 200w xcvr at just 20 watts out..and the eff
goes straight to hell,
and ditto with the TX imd. You really require a good 3-9db pad to run those
low power tetrodes
properly..when driven from your typ xcvr.
Later........ Jim VE7RF
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