6CD6 / 6BQ6 tubes good for amps?
Willy Krogstad
Would the 6CU6 (and it's like the 6BQ6GTB) be suitable for an audio
amplifier? I have some of these and wonder if they are keepers or not. And
what about the PL36?
I really appreciate your opinion..
Thanks,
Willy
Tubie
Well, I couldn't find much the 6CU6 and 6BQ6 in my book, but seems you
are asking for tv sweep pentodes ?
I myself have some limited experience with EL36s (quad set in a monoblock
as pentode class B push pull, Ua=300V, Ug2=150V) and I think the sound was
surprisingly good. A friend of mine compared a week ago some tubes as
PL36, EL84=6BQ5, EL86, PL84, PCL86 and found the PL36 a very interesting
tube, so he will investigate this a bit more.
The only problem with these tubes is low Ug2, so you have to stay pentode
mode with a separate supply. The pro is low Ua at high anode current, so the
amp will give you much more audio power from a given B+ supply.
Just giv'em a try.
tubie aka michael
"Willy Krogstad" <wi...@nt.telia.no> wrote in message
news:KBuE6.716$TAb.17...@news.telia.no...
RD
significant issue. You'll spend much more on a good pair of output
transformers and a high quality power supply. I love homebrew, but I
think it's important to keep the priorities in perspective. The 6BQ6
is in the same peak power class as the 6CA7 (EL34), but the latter is
a much superior device for this use. First, while the 6BQ6 has a high
peak current capability (which is the reason it's in the same class as
the 6CA7), its continuous duty plate dissipation is only 11 watts.
Also, it has a plate cap to contend with. Further, the 6CA7 has a
beautiful tone and is plentiful both new (good quality Russian) and
NOS. The Russan tubes are very reasonable, in fact a terrific deal in
my opinion. You will also find hudreds of schematics using the 6CA7
right here on the Web, more than sufficient to copy an existing
design, or to study for purposes of understanding the tube's exact
application. Finally, output transformers are available specifically
for the 6CA7, new and used, and that in itself can can save you tons
of grief.
RD
On Sun, 22 Apr 2001 06:10:50 GMT, "Willy Krogstad" <wi...@nt.telia.no>
wrote:
Jef Collin
PL36, that's a bw tv tube
Philips used them in PA amplifiers
i believe there is a circuit using them on www.tubebuilder.com
saw a guy on a radio fair a few months ago selling used pl36's together
with this circuit diagram
a sorry sight since he only had a handfull of pl36's and the circuit
diagram on his stand, nothing else..
i would keep em
jef
Kruse
Willy,
Sansui used the PL36 (that's also a 25E5) as an output tube in several
of their amps. The Sansui 1000 receiver (not to be confused with the
1000A) the 1000EA receiver and also another amp used this as an output
tube. The biggest advantage that this tube has is that it is still
cheap to purchase.
The Sansui 1000 still shows up on ebay quite a bit.
Dave
Remove (*) to email.
Patrick Turner
Anyway I have a stereo amp with two 6CM5 in each channel in triode,
and I get a very nice 22 watts per chan.
They were intended for line output in TV.
But they got used for a pile of things, as usual.
Patrick Turner.
Ian Iveson
"Tubie" <tu...@appelt4u.de> wrote in message
news:9bu0hg$kg3$1...@unlisys.unlisys.net...
> The only problem with these tubes is low Ug2, so you have to stay
pentode
> mode with a separate supply.
Or presumably you could use a seperate screen winding to give UL.
Come to think of it, would it be possible for a screen winding of
the same turns as the anode winding to be used to give triode
operation?
> The pro is low Ua at high anode current, so the
> amp will give you much more audio power from a given B+ supply.
Can you explain how this follows?
Thanks, Ian
Kelly Scott Molles
good and has good power. Nothing better than retubing your amp with NOS
tubes for $20!
Kelly
Kruse <kru*s...@kansas.net> wrote in message
news:zqzE6.23486$aW5.2...@dfw-read.news.verio.net...
Willy Krogstad
Hi!
Thanks for your response, fellows!
"Patrick Turner" <in...@turneraudio.com.au> wrote
> The PL36? Isn't that the same as EL36 or 6CM5?
I think so as for the EL36, but none of my (scarce) tube data books mentions
anything about 6CM5.
> Anyway I have a stereo amp with two 6CM5 in each channel in triode,
> and I get a very nice 22 watts per chan.
Is this really possible? 'cause Tubie said:
> The only problem with these tubes is low Ug2, so you have to stay pentode
> mode with a separate supply. The pro is low Ua at high anode current, so
the
> amp will give you much more audio power from a given B+ supply.
So it seems to me like this is two quite different tubes... But YOU are the
experts! I'm but a novice! However, my PL36 thingies looks more and more
like a candidate for experimentation. And the plate cap is of no concern, it
is only a little bit inconvenient (don't know how to spell this inconvenient
word!) - they are even solderable! :-)) Besides, all my homebrew aplifiers
are lethal to cats and small children anyway..
And Kruse said:
> Sansui used the PL36 (that's also a 25E5) as an output tube in several
> of their amps. The Sansui 1000 receiver (not to be confused with the
> 1000A) the 1000EA receiver and also another amp used this as an output
> tube.
So yes - your words really wet my apetite for some experimentation with the
PL36's! And yes - they are VERY cheap! Of course I know the real costs are
the iron, but that's not the point as I see it.
Willy.
Willy Krogstad
"Kelly Scott Molles" <mol...@jps.net> wrote
> I have a Sansui 1000 using PL36/25E5 output tubes. I think it's sounds
very
> good and has good power. Nothing better than retubing your amp with NOS
> tubes for $20!
20 dollars?? Do you have 15 pieces of output tubes in your amp?
:-)
Willy
Tubie
"Ian Iveson" <ianives...@virgin.net> wrote in message
news:kKDE6.5427$jh4.6...@news6-win.server.ntlworld.com...
>
> "Tubie" <tu...@appelt4u.de> wrote in message
> news:9bu0hg$kg3$1...@unlisys.unlisys.net...
>
> > The only problem with these tubes is low Ug2, so you have to stay
> pentode
> > mode with a separate supply.
>
> Or presumably you could use a seperate screen winding to give UL.
> Come to think of it, would it be possible for a screen winding of
> the same turns as the anode winding to be used to give triode
> operation?
Guess, this is not really triode operation, since Va swings by e.g.200VAC,
while
Vg2 must be much less due to DC at +150V.
> > The pro is low Ua at high anode current, so the
> > amp will give you much more audio power from a given B+ supply.
>
> Can you explain how this follows?
For a given B+ the max. voltage swing is limited by the tubes saturation
voltage.
This is usually arround 50V, sometimes less for pentodes as PL36, and much
higher for triodes. More voltage swing = more power.
This PL36 is also much higher current than e.g. a 6BQ5/EL84, so for max
power
we can use a much lower OT impedance - same as before, much more power.
This EL36 is rated about 12W dissipation as EL84. But max power in push pull
is
55 watts compared to 17 watts of EL84 - ok, I should mention, it's class B.
Best regards,
Tubie aka Michael
Robert Casey
an audio amp. In circuits with various B+'s.
Partway down the page I describe determining
a load impedance.
http://home.netcom.com/~wa2ise/radios/compaa3.html
Patrick Turner
But in triode you can use G2 tied to plate and up to 375 volts B+
In triode you get Ra = 600 ohms, u = 5 . Pd Quiescent should be
no more than 18 watts although the take about 28 watts before they
start to go red. They are pretty tough, with at least 0.5 amp cathode
current ability.
And they can be driven class Ab2 .
But two in class A1 give 22 watts easy and will give a pair of
KT66 tubes a job to keep up.
In tetrode they are not too good as distortion is higher than
other tetrodes. In UL they are ok, 35 watts is ok from a pair.
Patrick Turner.
Patrick Turner
They do tend to run away when the plate volts are over 375,
at say 425. 350 would be good.
Some tubes have a limit to how many plate volts can be
used before the grid bias just won't hold the current down,
no matter how negative you make the grid voltage.
But I've had my "junk box special" for 3 years and it's never missed a beat.
people who borowed it while I repaired their solid horrors didn't want
to let me have it back.
Like the 807 the screen volts can be higher than the rating
when triode connected.
Patrick Turner.
Preamp wrote:
> >
> >Hi!
> >Thanks for your response, fellows!
> >
> >
> >"Patrick Turner" <in...@turneraudio.com.au> wrote
> >
> >> The PL36? Isn't that the same as EL36 or 6CM5?
> >
> >I think so as for the EL36, but none of my (scarce) tube data books mentions
> >anything about 6CM5.
>
> 6CM5 is indeed the same as EL36. I have a guitar amp that uses them.
>
> >
> >> Anyway I have a stereo amp with two 6CM5 in each channel in triode,
> >> and I get a very nice 22 watts per chan.
> >
> >Is this really possible? 'cause Tubie said:
> >
> >> The only problem with these tubes is low Ug2, so you have to stay pentode
> >> mode with a separate supply. The pro is low Ua at high anode current, so
> >the
> >> amp will give you much more audio power from a given B+ supply.
> >
> >So it seems to me like this is two quite different tubes... But YOU are the
> >experts! I'm but a novice! However, my PL36 thingies looks more and more
> >like a candidate for experimentation. And the plate cap is of no concern, it
> >is only a little bit inconvenient (don't know how to spell this inconvenient
> >word!) - they are even solderable! :-)) Besides, all my homebrew aplifiers
> >are lethal to cats and small children anyway..
>
> I tried to use the 6CM5/EL36 in an SE amp in triode mode and fixed bias. They
> tried to burn themselves up (thermal runaway). I even tried pentode mode
> (similar circuit to EL34) and they did the same. I was told by someone that you
> have to get the screen down to about half B+ to make them stable.
>
> >
> >And Kruse said:
> >
> >> Sansui used the PL36 (that's also a 25E5) as an output tube in several
> >> of their amps. The Sansui 1000 receiver (not to be confused with the
> >> 1000A) the 1000EA receiver and also another amp used this as an output
> >> tube.
> >
> >So yes - your words really wet my apetite for some experimentation with the
> >PL36's! And yes - they are VERY cheap! Of course I know the real costs are
> >the iron, but that's not the point as I see it.
> >
> >
>
> I am sure they'll sound quite good.
David Crittle
<wi...@nt.telia.no> wrote:
Dear Willy
25 watt 6BQ6GTB audio amp:
Plate 300 VDC
Screen 150 VDC
Cathode bias resistor 270 ohms
Output transformer 4K P-P
Ralph McDiarmid
Any of those horizontal sweep tubes should make good audio output
tubes.
Willy Krogstad wrote in message ...
Andy Cuffe
>
> Very suitable.
>
> Any of those horizontal sweep tubes should make good audio output
> tubes.
>
McIntoch made a high power amp using something like 6 6JE6's as
outputs. I think it was 300W mono. The 6JE6 was a very common TV
horizontal tube.
--
Andy Cuffe
balt...@psu.edu