Will RF output (transmitter) be the same wattage as audio ou

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,
this 813 tube is rated at 250 to 300 watts output RF (per tube), but
running at around 700 to 750 volts on the plate.

I'm not planning to do this, but if this 813 tube was used in an audio
amplifier, and using 700 +/- plate voltage, would this tube be able to
put out around 250 to 300 watts audio power (per tube)? Yea, I know it
would require a custom audio output transformer.

Just curious.....

 

[Phil Allison]

olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


...... Phil

 

[Ralph Mowery]

In article <ru79bchvci6g6o18l8e4d4858jb03j3fek@4ax.com>,
oldschool@tubes.com says...

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,
this 813 tube is rated at 250 to 300 watts output RF (per tube), but
running at around 700 to 750 volts on the plate.

I'm not planning to do this, but if this 813 tube was used in an audio
amplifier, and using 700 +/- plate voltage, would this tube be able to
put out around 250 to 300 watts audio power (per tube)? Yea, I know it
would require a custom audio output transformer.

Just curious.....

Froim the data sheeds the 813 is only good for around 350 watts of audio
power with 2 of them in push pull with 2500 volts on the plates. Around
260 watts with 1500 watts on the plates for 2 of them.

I doubt they would make much power at all if only 700 volts were used on
the plates. The tubes are designed for over 1000 volts.

If running in anything resembling linear operation (RF or AF) that is
about all that can be gotten out of them and have them last. Running
class C at RF (audio would be very distorted) you can get more out of
them, but not 250 watts per tube with 700 volts on the plates.

 

[Michael A. Terrell]

Phil Allison wrote:

olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.

He asked about the 6L6, which will not come close to the 6L6GC in
performance.


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Phil Allison]

Michael Terrell wrote:

Phil Allison wrote:
olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,

** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.




..... Phil

 

[Phil Allison]

Michael Terrell wrote:

Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.

** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.



..... Phil

 

[Michael A. Terrell]

Phil Allison wrote:

Michael Terrell wrote:

Phil Allison wrote:
olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.

Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions. A lot of them were built with W.W. II surplus
tubes, of which the 6L6 was readily available as surplus into the '70s.

We aren't talking about stereos or guitar amps. The were audio
outputs for radios, or modulators for medium power AM transmitters
designed for Amateur radio service. I was servicing these radios back in
the '70s. That is four decades ago.


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Michael A. Terrell]

Phil Allison wrote:

Michael Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original 6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.



** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Clifford Heath]

On 01/03/17 16:26, Michael A. Terrell wrote:

Phil Allison wrote:
Michael Terrell wrote:
Phil Allison wrote:
Michael Terrell wrote:

Phil Allison wrote:
olds...@tubes.com wrote:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the
common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate
voltage,



** Versions of the 6L6GC made by RCA and Sylvania can be operated
in pairs in class B with 700V on the plate and 400V on the screens.

Audio output power can be 100W per pair in this mode, with low
distortion.

EL34s can also be used the same way to deliver 100W.

Guitar amps made by MusicMan and Dynacord are commercial examples.


He asked about the 6L6,


** The OP asked about "common audio output tubes" which the original
6L6 is not.

It's an all metal, museum piece.

6L6GCs have been the most common type sold for audio use for decades.



Yes, but the 'Amateur radio transmitters' he's talking about are from
the '40s and '50s, which were shipped with the original metal 6L6, not
the later glass versions.



** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this pissing match?

 

[Phil Allison]

Clifford Heath wrote:

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this pissing match?

** I only wanted to point out that regular 6L6 type tubes, as sold in the last 40 years, can output 100W per pair under the right supply conditions - something the data books do not mention.

It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly.

The 813 has fairly similar restrictions on the screen supply voltage.



..... Phil

 

>"It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down. If you go to 2X 700 volts, it might not be a matter of the tubes, it might be the tubes sockets.

What does limiting the G2 do ? Keep it from arcing to the suppressor grid ? I have wondered before about why the hell doesn't all this shit just arc and weld itself together. Well, OK I know it has to do with the vacuum, but still.

However wiki reports that permissivity of air at STP is only something like 1.000 point whatever, with 1 being the standard.

 

On Wed, 1 Mar 2017 17:18:14 +1100, Clifford Heath <no.spam@please.net>
wrote:

** Read correctly, the OP was not asking about transmitters at all.

The performance of some common tubes for audio output use was his topic.

QUOTE:

I was looking at some old 813 tubes that were once commonly used for
Amateur radio transmitters, as the final output tube. While the common
audio output tubes like 6L6 and 807 can produce about 25 to 30 watts
audio output (per tube), running around 300 to 450 volts plate voltage,

UNQUOTE:

So you agree, OP was not asking about transmitters?
He also wasn't asking about 6L6's of either type!
(though his reference to 30W/tube says he meant 6L6GC).

He was asking about 813 (transmitting) tubes in an audio amp.

Phil was right. Now can we please end this pissing match?

I just referred to the common audio output tubes. Wondering if a
transmitter tube (like an 813) is capable of audio output power in the
same wattage as that same tube would put out as a transmitter (asuming
the plate voltage, biasing, and signal input to the tube was about the
same.

From this thead, I did learn that these tubes need a lot higher plate
voltages than I thought (like 1500 to 2500 volts).

I also learned (after doing some research on the web), that the original
metal 6L6 tubes, did not have the same power output as the glass
version. &lt;&lt;<I NEVER KNEW THERE WAS A DIFFERENCE IN THE
CHARACTERISTICS>&gt;&gt; I thought they were the same tube in a different
container.

*** And this explains something that occurred 40 some years ago. When I
was running my tube power amps for my stereo, (four 6L6GC tubes
Push-Pull Parallel, in each mono block amp), one of the tubes went bad.
I went to my box of used tubes and found a 6L6 metal case, and used that
for a temporary replacement. Although that tube tested GOOD, the amp
just did not sound or perform properly. It did work, but lacked a lot of
the "punch" it had before. A few days later I bought a new 6L6GC, and
the amp worked great once again.

Now, 40 some years later, I learned why that metal 6L6 did not work
properly !!!!

I also learned in recent times that for best performance, a pair or quad
of output tubes should be MATCHED. Back then, I never knew anything
about matching. If it was the proper numbered tube, and a tube that
tested good, I'd just plug it in and GO....

 

[Ralph Mowery]

In article &lt;hbcdbcd458uti9s8s0hm9vnpsul65v6dap@4ax.com&gt;,
oldschool@tubes.com says...

I just referred to the common audio output tubes. Wondering if a
transmitter tube (like an 813) is capable of audio output power in the
same wattage as that same tube would put out as a transmitter (asuming
the plate voltage, biasing, and signal input to the tube was about the
same.

From this thead, I did learn that these tubes need a lot higher plate
voltages than I thought (like 1500 to 2500 volts).

I also learned (after doing some research on the web), that the original
metal 6L6 tubes, did not have the same power output as the glass
version. &lt;&lt;<I NEVER KNEW THERE WAS A DIFFERENCE IN THE
CHARACTERISTICS>&gt;&gt; I thought they were the same tube in a different
container.

*** And this explains something that occurred 40 some years ago. When I
was running my tube power amps for my stereo, (four 6L6GC tubes
Push-Pull Parallel, in each mono block amp), one of the tubes went bad.
I went to my box of used tubes and found a 6L6 metal case, and used that
for a temporary replacement. Although that tube tested GOOD, the amp
just did not sound or perform properly. It did work, but lacked a lot of
the "punch" it had before. A few days later I bought a new 6L6GC, and
the amp worked great once again.

Now, 40 some years later, I learned why that metal 6L6 did not work
properly !!!!

I also learned in recent times that for best performance, a pair or quad
of output tubes should be MATCHED. Back then, I never knew anything
about matching. If it was the proper numbered tube, and a tube that
tested good, I'd just plug it in and GO....

The short answer is that most of the tubes will put out the same power
at audio as they will at RF. Not counting some specific tubes such as
the microwave tubes. Tubes start loosing efficency as the frequency
goes higher into the RF ranges. The common 6146 tube might put out
about 50 watts up to about 50 MHz but will work to 150 MHz but only put
out 30 watts and stay within the ratings.

There is one other thing to look at. That is the class of service.
Running class C will put out the most power but can only be used for
certain types of RF signals due ot the distortion. It can not be used
at all for normal audio amplifiers.

As with the 813 tube, most tubes rated for much over 50 watts output
will often have a plate voltage of over 1000 volts,many like to have
2000 volts or more.

For the best sound the tubes should be matched. They are operated in
what is called a push-pull circuit. Often close to class B. That is
when one tube is putting out power,the other tube isn't during a cycle.
It is at the crossover point that if they are not well matched you get
most of the distortion. Many audio amps often operate more like AB
class to help eliminate that problem. It is not much of a problem at RF
due to the way the output circuit works.

 

[Phil Allison]

jurb...@gmail.com wrote:

"It all about raising up the plate supply voltage while keeping the
screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down.

** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power.

If you go to 2X 700 volts, it might not be a matter of the tubes,
it might be the tubes sockets.

** Most sockets can handle the extra voltage.

What does limiting the G2 do ?

** Keeps the screen current within limits.

Having the screens glowing bright is the biggest killer of power tubes.


..... Phil

 

[Michael A. Terrell]

jurb6006@gmail.com wrote:

"It all about raising up the plate supply voltage while keeping the screen supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the power, but also to try to keep the plate volage down. If you go to 2X 700 volts, it might not be a matter of the tubes, it might be the tubes sockets.

They used a lot of ceramic tube sockets in transmitters.

What does limiting the G2 do ? Keep it from arcing to the suppressor grid ? I have wondered before about why the hell doesn't all this shit just arc and weld itself together. Well, OK I know it has to do with the vacuum, but still.

However wiki reports that permissivity of air at STP is only something like 1.000 point whatever, with 1 being the standard.

--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Michael Black]

On Wed, 1 Mar 2017, Michael A. Terrell wrote:

jurb6006@gmail.com wrote:
"It all about raising up the plate supply voltage while keeping the screen
supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the
power, but also to try to keep the plate volage down. If you go to 2X 700
volts, it might not be a matter of the tubes, it might be the tubes
sockets.


They used a lot of ceramic tube sockets in transmitters.

ANd the really good tubes had plate caps.

Michael

 

On Wed, 1 Mar 2017 13:54:34 -0500, Michael Black &lt;et472@ncf.ca&gt; wrote:

On Wed, 1 Mar 2017, Michael A. Terrell wrote:

jurb6006@gmail.com wrote:
"It all about raising up the plate supply voltage while keeping the screen
supply under 400V - plus matching the load correctly. "

Seems to me to would have to load is pretty heavily, not just to get the
power, but also to try to keep the plate volage down. If you go to 2X 700
volts, it might not be a matter of the tubes, it might be the tubes
sockets.


They used a lot of ceramic tube sockets in transmitters.

ANd the really good tubes had plate caps.

Michael

I can relate to using ceramic sockets, because the standard ones would
likely burn up from such high voltages.
* What are the standard sockets made out of anyhow????

Considering the closeness of the tube socket pins, I could see where
there could be arcing between pins at voltages that are or exceed 1000V.
Plate caps eliminate that problem. However, I would assume that the wire
going to those plate caps would need to have insulation capable of the
voltage, and where they go thru the chassis, would need grommets that
can handle the voltage too. Not to mention the connections below the
chassis such as terminal strips.

I have not worked with any voltages exceeding 1000V (except the HV in
the old tv sets). But since I am on a farm, I know what an electric
fencer can do. If a fence wire gets too close to a tree (for example),
it will snap and shoot a spark a half inch long, or longer. Most of
those fencers are around 5000 V. Those fence wires are all run on
porcelin insultors. (although there are now plastic ones that work as
well).

I have felt them fences far too many times too..... I have been
literally knocked down from them more than once, if I was well
grounded.... NOT FUN.

Fortunately those fencers do not kill a person or animal (or we would
not use them, since livestock are expensive and dead people are not a
good thing). The voltage is high, but the current is low. (and it
pulses).

Anyhow, while I have not done it, I am sure building transmitters (or
anything else) using those high voltages, require special components and
wiring, which in itself requires special knowledge.

 

[Ralph Mowery]

In article &lt;t37ebcpgloi0idj7v42jksdni0v7jd9277@4ax.com&gt;,
oldschool@tubes.com says...

I can relate to using ceramic sockets, because the standard ones would
likely burn up from such high voltages.
* What are the standard sockets made out of anyhow????

Considering the closeness of the tube socket pins, I could see where
there could be arcing between pins at voltages that are or exceed 1000V.
Plate caps eliminate that problem. However, I would assume that the wire
going to those plate caps would need to have insulation capable of the
voltage, and where they go thru the chassis, would need grommets that
can handle the voltage too. Not to mention the connections below the
chassis such as terminal strips.

I have not worked with any voltages exceeding 1000V (except the HV in
the old tv sets). But since I am on a farm, I know what an electric
fencer can do. If a fence wire gets too close to a tree (for example),
it will snap and shoot a spark a half inch long, or longer. Most of
those fencers are around 5000 V. Those fence wires are all run on
porcelin insultors. (although there are now plastic ones that work as
well).

I have felt them fences far too many times too..... I have been
literally knocked down from them more than once, if I was well
grounded.... NOT FUN.

Fortunately those fencers do not kill a person or animal (or we would
not use them, since livestock are expensive and dead people are not a
good thing). The voltage is high, but the current is low. (and it
pulses).

Anyhow, while I have not done it, I am sure building transmitters (or
anything else) using those high voltages, require special components and
wiring, which in itself requires special knowledge.

I have 2 amplifiers for my ham radios. Both have about 2700 volts on
the plates of the tubes. The current drawn by the tubes is almost one
amp. I have worked on them several times. To do that I make sure the
capacitors have fully discharged by watching the voltmeter on the amps
go near zero. When I take the cover off, vurey carefully, I then short
the capacitors to ground to make sure the volt meter is not giving a
false reading. The voltage and current is not like a fence charger. It
will dump a lot of current into you and often kill. Fence chargers are
more like a static electricity shock, lots of voltage,but little
current. They are made to shock and not to kill.

It does take some special insulated wire for the amps and other high
voltage items. Most common wires are insulated for around 600 volts or
even 300 volts. That 2700 volts will often burn through wire insulated
like that . Only 'good' thing about it,is that it will not jump much of
an air gap. However with RF applied the operaing voltages inside the
amp is somewhat greater and can arc a short distance.

Most of the tubes operate with less than 500 volts on the pins with the
higher voltage going to the cap on the plates. Ceramic is often used
because of the heat on the pins of the tubes. The filiments get hot and
direct transfer heat, and the heat of the plate is radiated to some
extent. Afer all, if an amp is putting out 1000 watts it is using close
to 1500 to 2000 watts to do it. That is almost as much as some of the
smaller 'bathroom' portable electric heaters put out.

 

&gt;"** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power. "

I think you got this fucked up somehow. When the load impedance is halved then the power is doubled. I'll put it down as a typing error unless you argue the point.

What's more, double the voltage into the same load if four times the power, not two.

&gt;"Having the screens glowing bright is the biggest killer of power tubes."

Perhaps you are older and thus have more knowledge then I on some of this. From what I understood from the old days, tubes (valves) generally break down due to the cathode nit being able to put out current, and that is where all the current comes from.

However of course there can be other failure modes. Are you saying that some sort of arc or leakage is damaging the valve ? If so I would like your explanation of this failure mode.

 

[Phil Allison]

jurb...@gmail.com wrote:

"** The load impedance is doubled, since the max tube current cannot increase.

Double voltage into double load = double the power.

I think you got this fucked up somehow.

** Like hell I did.

Try reading it AGAIN !!!

IF you double the voltage into double the load, the CURRENT stays the same.

But double the voltage at the same current is TWICE the power.

Power = V x I

"Having the screens glowing bright is the biggest killer of power tubes."


Perhaps you are older and thus have more knowledge then I on some of
this. From what I understood from the old days, tubes (valves)
generally break down due to the cathode nit being able to put out
current, and that is where all the current comes from.

However of course there can be other failure modes. Are you saying
that some sort of arc or leakage is damaging the valve ?

** Any data sheet will quote max screen dissipation - usually only a few watts.

The fine steel wire will glow red or even white if the rating is exceeded.

Then guess what happens ??

If the screen supply voltage is too high, it take excessive current whenever the plate voltage swings low under load.

Data sheets reveal this as an increase in AVERAGE screen current at max signal.

Screen dissipation = V x I average.



..... Phil