500V on EL84 plates? Anyone?
Shiva
(EL84's) in the simplest way (read - fewest relay contacts). Thus far, I'm
thinking of simply connecting an alternate set of screens - keeping the
plates always connected in both sets of tubes. a couple of problems: the
output tranny's got ~500V on it, and all the data I see on EL84's doesn't go
much past 300V. Has anyone had any experience with EL84's with 500V on the
plates? This is going to be a distortion channel for a guitar amp, so I'm
not too concerned with low dist. ##'s<stupid grin> or max. power (impedance
mismatch's fine by me). Would a couple of bypassed resistors on plates make
any sense? Any circuits using similar voltages? Any and all comments
wellcome...
-dim (now that all the bugs are out...)
RonSonic
>I was thinking ofswitching from one set of output tubes (el34's) to another
>(EL84's) in the simplest way (read - fewest relay contacts). Thus far, I'm
>thinking of simply connecting an alternate set of screens - keeping the
>plates always connected in both sets of tubes. a couple of problems: the
>output tranny's got ~500V on it, and all the data I see on EL84's doesn't go
>much past 300V. Has anyone had any experience with EL84's with 500V on the
>plates? This is going to be a distortion channel for a guitar amp, so I'm
>not too concerned with low dist. ##'s<stupid grin> or max. power (impedance
>mismatch's fine by me).
I'm scared. I've seen EL84 (7189 really) run to 400, but I don't like
it and 500 is really alarming.
Ron
Gregg
--
Gregg
On Fri, 05 Jul 2002 03:17:06 GMT, "Shiva" <help...@666.com> wrote:
Xavier van Unen
> snip
> Has anyone had any experience with EL84's with 500V on the
> plates? This is going to be a distortion channel for a guitar amp, so I'm
> not too concerned with low dist. ##'s<stupid grin> or max. power
(impedance
> mismatch's fine by me).
Mind you they didn't last very long, but they were set at plate dissipation
of around 11W. I wonder how long the JJ EL84's I installed will survive (at
a static plate dissipation of 9W).
Regards Xavier.
Mark
"Gregg" <nos...@unknown.com> wrote in message
news:3d252d97...@news.telus.net...
> Can you tape it and post the spectacular fireworks video for us?
>
> --
> Gregg
My thoughts exactly :)
Nick Sheldon
DISCLAIMER: I AM NOT ADVISING YOU TO USE 500 VOLTS OR ANY OTHER VALUE OF HT
IN EXCESS OF THE SPEC.
I have used EL84s at 900v and beyond without problems, but only
experimentally. A PCL86 based PPP amp detonated at 1730v.
See www.bigvalveamplifiers.co.uk
Best wishes
Nick Sheldon
Shiva wrote in message ...
Patrick Turner
Shiva wrote:
Musical Reference put out an amp with two x EL84 per channel, with
700 volts B+, and 350 v for Eg2, and they have 5% CFB windings on the
output tranny.
The RLa-a is 14 kOhms, and poer output I measured on one at clip was 36 watts.
Idle Pd was 700v x 12 mA of idle current.
Gut busting from pidler tubes.
Remember to have a 0.25 amp fuse in the common cathode circuit.
Patrick Turner.
Shiva
ratings? I had an amp running a quartet of Svetlana 6L6's at over 700V
plate, grid-biased, and had *no* problems. I was thinking of doing
something else with those tube sockets, but now I'm determined to, at least,
make the thing run on EL84's and send folks a picture of a voltmeter, a
scope, and a distortion analyzer with the amp running at full tilt (without
overdriving the output). Will do it within a few days (I should be working
now), and, if fireworks happen, Greg will get to see that too...
-dim
"Nick Sheldon" <nick.s...@sheldonassociate.demon.co.uk> wrote in message
news:1025851759.13249....@news.demon.co.uk...
Shiva
el84's... I'm committed (or should be) now.
-dim
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:3D2582F5...@turneraudio.com.au...
Ian Iveson
EL84 guitar amp design in his book.
450V, 20mA each, pentode pp, with 2.7k on each screen.
Shows a picture of the man himself playing a 335 (I think). He does
not appear a radical kind of chap. Doesn't look like he's much into
distortion. He does say that it survives overdrive though. Seems
silly to use a torroid but he sells them...
cheers, Ian
"Shiva" <help...@666.com> wrote in message
news:Sc8V8.5774$jr3....@nwrddc02.gnilink.net...
Shiva
testing ( a bit burnt out) BUT:
No fireworks, Greg... This is how it breaks down:
501V on the plates through a 1ohm resistor (to measure pure plate
urrent). -14.9 bias through 2.6k snubber resistor (was thinking of 1.5K,
but had no new ones left...) to get clean 1Khz sine, 331V on the screens
from an unregulated supply (the spot that feeds my phase splitter - doesn't
seem to bother it any - no substantial voltage sag) through a pair of 470ohm
2W resistors (one for each screen - had them handy...), and the cathodes
tied to ground through a 1 ohm (to get total current).
The sound? Didn't do much clean playin', but *plenty* of volume & a bit
too brittle, but then I had to keep the preamp levels *way8 lower than i did
for EL34's. But the overdrive is *awesome*. You can get anything from
Delux-y snort & growl to full-out marsh sizzlatron to highwatty ring (the
whole amp sounds very hiwatty - maybe it's the Partridges & high voltage...)
Anyhow, i had the EL34's pulled for this, but just as a precaution - need
to have a switchable bias supply too...
Fred, remember we were wondering what would happen if the screens were
left floating? Well, here's the answer - with the screens tied through
their 470 ohm resistors to a 12" chunk of wire, you could still get the tube
to conduct a bit - what you see on the sope is something like a *way*
overbiased tube set (sort'a a square wave if you totaly overdrive the input,
about 1/100's of full power with the screens connected. Goes away when you
ground the screens... Will hopefully post some distortion - actual power
data tomorrow - but, thus far, I'm impressed that nothing is glowing &
nothing is arcing & the sound's pretty nifty - more like a 7591(? - the
ampeg lil' tube) than a 6V6
So - Max ratings? Bwah... Haven't seen a deacent guitar amp which took
them seriously...
-dim
RonSonic
Wow.
Thanks for the after-action report. I wouldn't of thunk they'd live.
Ron
Nick Sheldon
DISCLAIMER: DON'T DO THIS!
My domestic use single case-amp (avoids having leads carrying EHT from one
unit to another - I have a two-year-old with extreme technical capability
and no sense of danger) uses an HT of 1360v and PCL86s (max HT supposedly
around 250-300v).
No problem!
Do you remember the old adage about rocket engineers? They all clapped when
a new engine didn't immediately explode ... and I get these strange dreams
about fire, thunder and speaking with a German accent ;-)
Best wishes
Nick Sheldon
Shiva wrote in message ...
Ned Carlson
I believe you'll be fine so long as you hold the screen voltage down
to a reasonable (and preferably regulated) level, like say 300V
or below, and use a resonable plate current (which is going to be
rather low so as to not push the plate dissipation) .
However, you should be prepared to sacrifice a few
to the great Experimental Amp God Of Science.
Ned Carlson Triode Electronics "where da tubes are!"
5633 W Irving Park Rd Chicago, IL, 60634 USA
ph 773-871-7459 fax 773-871-7938
11:00 to 7:00 PM CT (1700-0100 UTC) M-F
http://www.triodeelectronics.com
"Beer is proof that God loves us and wants
us to be happy."
Benjamin Franklin
Shiva
"Ned Carlson" <postm...@triodeel.com> wrote in message
news:3d2ba96e...@news-west.newscene.com...
Hey Ned - it actually worked so well that I'm hooked on building EL84 Amps.
Just finished a SE Champ-ish amp (well, they're never finished unless
they're sold...). What a great tube! And hooked up as a triode (set up a
switch in the SE amp), the thing doesn't require more drive voltage (well,
it does, but it still overdrives quite nicely with the same driver). With
385V on the plates (in the SE amp, cathode bias in this one), it even acts
like a flaky triode *with screens floating*. Go figgah...
-dim.
Jim McShane
> Hey Ned - it actually worked so well that I'm hooked
> on building EL84 Amps. Just finished a SE Champ-ish
> amp (well, they're never finished unless they're sold...).
> What a great tube
If you want to try another similar tube that is a bit heavier duty
(and cheaper!) try the 6GK6. It's a 9 pin tall miniature like
an EL84, with a 13.2 watt plate dissipation rating.
Another great overlooked cheap DIY tube.
Jim McShane
Need NOS or New Tubes? Got a H-K Citation (Pre) Amp?
See my web pages at http://pages.prodigy.net/jimmcshane
Shiva
"Jim McShane" <jimmc...@prodigy.net> wrote in message
news:vQZW8.3539$EE5.14...@newssvr17.news.prodigy.com...
> "Shiva" <help...@666.com> wrote...
>
> > Hey Ned - it actually worked so well that I'm hooked
> > on building EL84 Amps. Just finished a SE Champ-ish
> > amp (well, they're never finished unless they're sold...).
> > What a great tube
>
> If you want to try another similar tube that is a bit heavier duty
> (and cheaper!) try the 6GK6. It's a 9 pin tall miniature like
> an EL84, with a 13.2 watt plate dissipation rating.
>
> Another great overlooked cheap DIY tube.
>
> Jim McShane
Thanks Jim - the thing is, i get some tubes at cost, but only the ones
commonly used in guitah' stuff (from the music store I work through). I
also never throw old tubes out ("are you *sure* you want a full retube? The
tubes are perfectly good, you won't hear any difference. ... OK, it's your
money. ... A what? A Mullard GZ34? Why? ... OK."), so I have bins and
bins of old tubes... Though nothing exotic (unless you count OOS (old old
stock) neat-o tubes (a bit of everything, but for some reason I've collected
a whole bunch of Telefunken 12a*7's, and some that even could be new (i got
them with a bunch of ancient test gear, in boxes, but the boxes are
*wrong*... marked "Simens" or something...))(matching parenthesis?).
So I'm stuck with using common tubes. Other than one failed (aborted)
attempt to use some 2E26's my friend gave me... Someone said they had a
great audio amp running those, but i couldn't figure oout why the screens
drew such ridiculously high current at only 200V... I'll get them going
when I have some free time... Now back to bread & butter...
-dim
Choky
why don't ya try 0.63A fuse instead 6.3A ?
hehehe...................
--
Choky
Prodanovic Aleksandar
choky*remove*@eunet.yu
YU
-------------------------------
remove *remove* to reply!
-------------------------------
"Shiva" <help...@666.com> wrote in message news:Sc8V8.5774$jr3....@nwrddc02.gnilink.net...
Choky
--
Choky
Prodanovic Aleksandar
choky*remove*@eunet.yu
YU
-------------------------------
remove *remove* to reply!
-------------------------------
"Nick Sheldon" <nick.s...@sheldonassociate.demon.co.uk> wrote in message
news:1025851759.13249....@news.demon.co.uk...
Doug Schultz
is it a computer virus causing it or is it entirely tube related
Doug