7-pin EL84
Alex
I would like to get an output pentode or beam tetrode in a 7-pin glass
envelope for a radio project.
6AQ5 is the most known tube, equivalent to 6V6. Also there exists a 6AR5
which is quite feeble -- only 8.5W dissipation and 2.3mA/V
transconductance -- sort of miniature equivalent of 6F6.
I would like to have a higher transconductance. I am wondering, do 7-pin
output (audio or video) pentodes exist with higher transconductance,
6...15mA/V and decent plate disssipation, say >9W?
I remember vaguely to have come across some tube, with four digit numeric
designation, starting with "7", which was allegedly similar to EL84.
Who has more accurate information, please?
Regards,
Alex
Phil Allison
"Alex"
>
> 6AQ5 is the most known tube, equivalent to 6V6. Also there exists a 6AR5
> which is quite feeble -- only 8.5W dissipation and 2.3mA/V
> transconductance -- sort of miniature equivalent of 6F6.
>
> I would like to have a higher transconductance. I am wondering, do 7-pin
> output (audio or video) pentodes exist with higher transconductance,
> 6...15mA/V and decent plate disssipation, say >9W?
** The 6AQ5 hs a 12 watt plate rating:
http://www.tubezone.net/pdf/6aq5el90.pdf
Plus 2 watt screen rating.
> I remember vaguely to have come across some tube, with four digit numeric
> designation, starting with "7", which was allegedly similar to EL84.
** Sure.
Bet your ass it was not a 7 pin miniature.
.... Phil
Peter Wieck
a) The EL84/6BQ5/7189 I believe is what you mean in your last
paragraph before the question. It is a nine (9) pin base (tall)
miniature.
b) http://hereford.ampr.org/Tube4.php?tube=6AQ5 Data for the 6AQ5.
With substitutions if you wish.
c) Us the above link, insert tube numbers, you will get the data you
need for the most part.
Peter Wieck
Melrose Park, PA
John Byrns
"Alex" <apog...@bigpond.com> wrote:
The 6CU5 has a higher transconductance at 7.5 mA/V, but a low plate dissipation
rating.
--
Regards,
John Byrns
Surf my web pages at, http://fmamradios.com/
Patrick Turner
The 6AR5 and 6AQ5 were great replacements for a much more expensive 6V6
or EL84. Price determined what went into radios.
So if you had a small beam tube idling at only 6W, it could make 2.5W of
audio PO easily, and since the lightweight coned 4" or 6" speakers used
in 1955 had a 1kHz sensitivity of 95dB, then 2W at the speaker was
plenty. I have such a radio and it sounds well.
I don't know what tube you want though that has a higher gm and Pda.
Try searching in the RCA tube manuals and others where they group the
output tubes together.
Bearing in mind what has been said elsewhere about pentodes with SS CCS
etc today at r.a.t, perhaps you could have a 6AR5 used as a triode
with a choke feed from +350Vdc, but with a mosfet RC coupled to the
anode and with say 60mA of Id from a B+ = 500V so that an OPT is driven
off the mosfet source which is of course very low output resistance. The
OPT is between source and 0V, with mosfet appropriately biased and with
heat sink for whatever watts you want to suit the ac load.
Patrick Turner.
Patrick Turner
You are right again Phil. 6AQ5 is *the same* as 6V6 acording to the
specs which say with Ea = 250V, Ia = 47mA,
then RL = 5k, PO at the anode = 4.5W at 8% THD. This means Pda = 11.75W,
anode effciency = 38%.
Slightly higher Ea, lower ia, and higher RL and NFB can force the tube
to be more efficient and you get up to about 5.5W.
Feeble transconductance with 6AQ5 and 6V6 does not matter. These are
still easy tubes to drive with any little triode such as 6AV6 or like
types.
Patrick Turner.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
Couldn't you just as well use a suitable tube in that circuit?
Alex
> On Oct 15, 5:10 am, "Alex" <apogo...@bigpond.com> wrote:
>
>
>
>
>
> > Hello.
>
> > I would like to get an output pentode or beam tetrode in a 7-pin glass
> > envelope for a radio project.
>
> > 6AQ5 is the most known tube, equivalent to 6V6. Also there exists a 6AR5
> > which is quite feeble -- only 8.5W dissipation and 2.3mA/V
> > transconductance -- sort of miniature equivalent of 6F6.
>
> > I would like to have a higher transconductance. I am wondering, do 7-pin
> > output (audio or video) pentodes exist with higher transconductance,
> > 6...15mA/V and decent plate disssipation, say >9W?
>
> > I remember vaguely to have come across some tube, with four digit numeric
> > designation, starting with "7", which was allegedly similar to EL84.
>
> > Who has more accurate information, please?
>
> > Regards,
> > Alex
>
> a) The EL84/6BQ5/7189 I believe is what you mean in your last
> paragraph before the question. It is a nine (9) pin base (tall)
> miniature.
>
> With substitutions if you wish.
>
> c) Us the above link, insert tube numbers, you will get the data you
> need for the most part.
>
> Peter Wieck
>
> - Show quoted text -
Thanks, Peter.
6DS5 would suit me. Transconductance is higher than of 6AQ5.
I will check if can find them in Australia. At "tubedepot" they are
not expensive.
Regards,
Alex
Alex
> In article <VriJk.5695$sc2.4...@news-server.bigpond.net.au>,
>
> - Show quoted text -
This one is only rated to 150V on the plate and... a little bit
inefficient (like a steam engine): dissipates more on the heater
(6.3V, 1.2A!) than on the plate.
Engineers must have worked hard to design such a thing. Probably the
only way they could achieve high emission at low screen voltage was to
increase cathode surface area.
Alex
BretLudwig
harder to find than 9 pin ones????????? No one makes 7 pinners much
anymore whereas 9 pin is very much in new production. There is no 7 pin
type in common use any more in new production to my knowledge.
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Si.
"John Byrns" <byr...@sbcglobal.net> wrote in message
news:byrnsj-42C79E....@newsclstr03.news.prodigy.net...
Hi all,
The 6005 was 7 pin and 12W anode dissipation I found some for peanuts on
ebay not so long ago...
http://frank.pocnet.net/sheets/093/6/6005.pdf
Si.
John Byrns
"Si." <blu_g...@hotmail.co.uk> wrote:
Isn't the 6005 just a 6AQ5 with a different name?
Alex
"BretLudwig" <bratz...@gmx.us> wrote in message
news:fdb1f569f6b21c05...@localhost.talkaboutaudio.com...
> Just why do you want to use a 7 pin miniature socket when they are much
> harder to find than 9 pin ones????????? No one makes 7 pinners much
> anymore whereas 9 pin is very much in new production. There is no 7 pin
> type in common use any more in new production to my knowledge.
I wanted to use the existing radio chassis where the output tube is a
7-pinner and mounted on the PCB. Changing the socket to 9-pin is bit messy.
Regards,
Alex