> On Sat, 6 Jun 2020 15:05:31 +0300, Tauno Voipio
> <tauno.voipio@notused.fi.invalid> wrote:
>
>> On 5.6.20 22:13, upsidedown@downunder.com wrote:
>>> On Fri, 5 Jun 2020 07:06:37 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> On 2020-06-04 21:03, John S wrote:
>>>>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>>>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>>>>> boomer#...@none.com wrote:
>>>>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>>>>> output?
>>>>>>>>>
>>>>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>>>>> tubes,
>>>>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>>>>> looking into other possible tubes.
>>>>>>>>>
>>>>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>>>>>> but
>>>>>>>>> after careful research, it's almost identical, but with a different
>>>>>>>>> envelope (plate on the top cap).
>>>>>>>>>
>>>>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>>>>> from
>>>>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>>>>> RMS (per channel).
>>>>>>>>
>>>>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>>>>>> but that is what was powering the amps. I owned two of them . We
>>>>>>>> would use them for bass guitar or the PA.
>>>>>>>
>>>>>>> Megawatt AM modulators.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>>>>> of America) used a modulator tube to vary the B+ on the Class C final
>>>>>> amplifer. IIRC that improved the efficiency by about 2x compared with
>>>>>> lower level modulation and linear amplification.
>>>>>
>>>>> IIRC, it was known as Heising modulation.
>>>>
>>>> I'd never heard the term, but a web search brings up screen-grid
>>>> modulation examples, e.g.
>>>> <http://www.w8ji.com/Heising%20modulation.htm>.
>>>>
>>>> Plate modulation is different, because it doesn't require the final to
>>>> be running in a linear mode. AM is inherently inefficient, but using a
>>>> Class A linear amp for the final wastes at least 75% of the electrical
>>>> power.
>>>
>>> If you have a tank circuit after the tube, you can run the tube in
>>> class AB, which has a higher efficacy.
>>>
>>>> Plate modulation only wastes half, which (if all you've got is
>>>> tubes) makes it a huge win.
>>>
>>> The final tube can run in class C, with a high efficiency, but the
>>> question is how to generate the high audio power. This has now been
>>> done for decades with semiconductors and some digital methods.
>>>
>>> For instance the Brown Boveri (now ABB) 500 kW HF or 600 kW MF
>>> transmitters from the 1980's used 32 floating power supplies in series
>>> feeding the plate. Depending of the instant audio waveform amplitude,
>>> 1-32 of these power supplies were actually activated, thus varying the
>>> plate voltage based on the audio waveform.
>>
>>
>> A plate (and screen) modulated AM tube Class C amplifier needs an
>> audio power of half of the carrier-level DC input power to the PA.
>>
>> For a 500 kW carrier output, the input power is around 650 - 700 kW,
>> and the modulator output needed will be around 350 kW, whatever means
>> are used to create it.
>
> This is very apparent when a modulation transformer is used.
>
>> The RF excitation and output tank must be dimensioned to create
>> 4 times of the no-modulation carrier power at the positive modulation
>> peaks (PEP, peak envelope power).
>
> When an audio controlled power supply is used, the whole power flows
> through the power supply, Compare it to a HVDC generator. Instead of
> generating a 50/60 Hz sine wave, a biased audio waveform feeds the
> output tube. Both the switching mode power supply as well as the class
> C tube can run at a high efficiency.
A 100% sine-wave modulated AM signal has an average power of 1.5 times
the carrier power. The extra 50% comes from the modulator, regardless
how the modulator output stage is configured.
--
-TV
Reply by ●June 6, 20202020-06-06
On Sat, 6 Jun 2020 15:05:31 +0300, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:
>On 5.6.20 22:13, upsidedown@downunder.com wrote:
>> On Fri, 5 Jun 2020 07:06:37 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> On 2020-06-04 21:03, John S wrote:
>>>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>>>> wrote:
>>>>>>
>>>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>>>> boomer#...@none.com wrote:
>>>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>>>> output?
>>>>>>>>
>>>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>>>> tubes,
>>>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>>>> looking into other possible tubes.
>>>>>>>>
>>>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>>>>> but
>>>>>>>> after careful research, it's almost identical, but with a different
>>>>>>>> envelope (plate on the top cap).
>>>>>>>>
>>>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>>>> from
>>>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>>>> RMS (per channel).
>>>>>>>
>>>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>>>>> but that is what was powering the amps. I owned two of them . We
>>>>>>> would use them for bass guitar or the PA.
>>>>>>
>>>>>> Megawatt AM modulators.
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>>>> of America) used a modulator tube to vary the B+ on the Class C final
>>>>> amplifer.� IIRC that improved the efficiency by about 2x compared with
>>>>> lower level modulation and linear amplification.
>>>>
>>>> IIRC, it was known as Heising modulation.
>>>
>>> I'd never heard the term, but a web search brings up screen-grid
>>> modulation examples, e.g.
>>> <http://www.w8ji.com/Heising%20modulation.htm>.
>>>
>>> Plate modulation is different, because it doesn't require the final to
>>> be running in a linear mode. AM is inherently inefficient, but using a
>>> Class A linear amp for the final wastes at least 75% of the electrical
>>> power.
>>
>> If you have a tank circuit after the tube, you can run the tube in
>> class AB, which has a higher efficacy.
>>
>>> Plate modulation only wastes half, which (if all you've got is
>>> tubes) makes it a huge win.
>>
>> The final tube can run in class C, with a high efficiency, but the
>> question is how to generate the high audio power. This has now been
>> done for decades with semiconductors and some digital methods.
>>
>> For instance the Brown Boveri (now ABB) 500 kW HF or 600 kW MF
>> transmitters from the 1980's used 32 floating power supplies in series
>> feeding the plate. Depending of the instant audio waveform amplitude,
>> 1-32 of these power supplies were actually activated, thus varying the
>> plate voltage based on the audio waveform.
>
>
>A plate (and screen) modulated AM tube Class C amplifier needs an
>audio power of half of the carrier-level DC input power to the PA.
>
>For a 500 kW carrier output, the input power is around 650 - 700 kW,
>and the modulator output needed will be around 350 kW, whatever means
>are used to create it.
This is very apparent when a modulation transformer is used.
>The RF excitation and output tank must be dimensioned to create
>4 times of the no-modulation carrier power at the positive modulation
>peaks (PEP, peak envelope power).
When an audio controlled power supply is used, the whole power flows
through the power supply, Compare it to a HVDC generator. Instead of
generating a 50/60 Hz sine wave, a biased audio waveform feeds the
output tube. Both the switching mode power supply as well as the class
C tube can run at a high efficiency.
Reply by John S●June 6, 20202020-06-06
On 6/5/2020 6:06 AM, Phil Hobbs wrote:
> On 2020-06-04 21:03, John S wrote:
>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>> wrote:
>>>>
>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>> boomer#...@none.com wrote:
>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>> output?
>>>>>>
>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>> tubes,
>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>> looking into other possible tubes.
>>>>>>
>>>>>> At one time, I thought the 807 tube was more powerful than the
>>>>>> 6L6, but
>>>>>> after careful research, it's almost identical, but with a different
>>>>>> envelope (plate on the top cap).
>>>>>>
>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>> from
>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around
>>>>>> 120W
>>>>>> RMS (per channel).
>>>>>
>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>> looked up the RCA8000 and it was not listed as an audio output
>>>>> tube, but that is what was powering the amps. I owned two of them .
>>>>> We would use them for bass guitar or the PA.
>>>>
>>>> Megawatt AM modulators.
>>>>
>>>>
>>>>
>>>
>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>> of America) used a modulator tube to vary the B+ on the Class C final
>>> amplifer. IIRC that improved the efficiency by about 2x compared
>>> with lower level modulation and linear amplification.
>>
>> IIRC, it was known as Heising modulation.
>
> I'd never heard the term, but a web search brings up screen-grid
> modulation examples, e.g.
> <http://www.w8ji.com/Heising%20modulation.htm>.
>
> Plate modulation is different, because it doesn't require the final to
> be running in a linear mode. AM is inherently inefficient, but using a
> Class A linear amp for the final wastes at least 75% of the electrical
> power. Plate modulation only wastes half, which (if all you've got is
> tubes) makes it a huge win.
>
> Cheers
>
> Phil Hobbs
>
Sorry, Phil. I meant Doherty amplifier. Been too many years since I
worked as a transmitter "baby sitter".
Reply by Tauno Voipio●June 6, 20202020-06-06
On 5.6.20 22:13, upsidedown@downunder.com wrote:
> On Fri, 5 Jun 2020 07:06:37 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 2020-06-04 21:03, John S wrote:
>>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>>> wrote:
>>>>>
>>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>>> boomer#...@none.com wrote:
>>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>>> output?
>>>>>>>
>>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>>> tubes,
>>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>>> looking into other possible tubes.
>>>>>>>
>>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>>>> but
>>>>>>> after careful research, it's almost identical, but with a different
>>>>>>> envelope (plate on the top cap).
>>>>>>>
>>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>>> from
>>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>>> RMS (per channel).
>>>>>>
>>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>>>> but that is what was powering the amps. I owned two of them . We
>>>>>> would use them for bass guitar or the PA.
>>>>>
>>>>> Megawatt AM modulators.
>>>>>
>>>>>
>>>>>
>>>>
>>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>>> of America) used a modulator tube to vary the B+ on the Class C final
>>>> amplifer. IIRC that improved the efficiency by about 2x compared with
>>>> lower level modulation and linear amplification.
>>>
>>> IIRC, it was known as Heising modulation.
>>
>> I'd never heard the term, but a web search brings up screen-grid
>> modulation examples, e.g.
>> <http://www.w8ji.com/Heising%20modulation.htm>.
>>
>> Plate modulation is different, because it doesn't require the final to
>> be running in a linear mode. AM is inherently inefficient, but using a
>> Class A linear amp for the final wastes at least 75% of the electrical
>> power.
>
> If you have a tank circuit after the tube, you can run the tube in
> class AB, which has a higher efficacy.
>
>> Plate modulation only wastes half, which (if all you've got is
>> tubes) makes it a huge win.
>
> The final tube can run in class C, with a high efficiency, but the
> question is how to generate the high audio power. This has now been
> done for decades with semiconductors and some digital methods.
>
> For instance the Brown Boveri (now ABB) 500 kW HF or 600 kW MF
> transmitters from the 1980's used 32 floating power supplies in series
> feeding the plate. Depending of the instant audio waveform amplitude,
> 1-32 of these power supplies were actually activated, thus varying the
> plate voltage based on the audio waveform.
A plate (and screen) modulated AM tube Class C amplifier needs an
audio power of half of the carrier-level DC input power to the PA.
For a 500 kW carrier output, the input power is around 650 - 700 kW,
and the modulator output needed will be around 350 kW, whatever means
are used to create it.
The RF excitation and output tank must be dimensioned to create
4 times of the no-modulation carrier power at the positive modulation
peaks (PEP, peak envelope power).
--
-TV
Reply by Phil Hobbs●June 5, 20202020-06-05
On 2020-06-05 15:13, upsidedown@downunder.com wrote:
> On Fri, 5 Jun 2020 07:06:37 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 2020-06-04 21:03, John S wrote:
>>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>>> wrote:
>>>>>
>>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>>> boomer#...@none.com wrote:
>>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>>> output?
>>>>>>>
>>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>>> tubes,
>>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>>> looking into other possible tubes.
>>>>>>>
>>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>>>> but
>>>>>>> after careful research, it's almost identical, but with a different
>>>>>>> envelope (plate on the top cap).
>>>>>>>
>>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>>> from
>>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>>> RMS (per channel).
>>>>>>
>>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>>>> but that is what was powering the amps. I owned two of them . We
>>>>>> would use them for bass guitar or the PA.
>>>>>
>>>>> Megawatt AM modulators.
>>>>>
>>>>>
>>>>>
>>>>
>>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>>> of America) used a modulator tube to vary the B+ on the Class C final
>>>> amplifer. IIRC that improved the efficiency by about 2x compared with
>>>> lower level modulation and linear amplification.
>>>
>>> IIRC, it was known as Heising modulation.
>>
>> I'd never heard the term, but a web search brings up screen-grid
>> modulation examples, e.g.
>> <http://www.w8ji.com/Heising%20modulation.htm>.
>>
>> Plate modulation is different, because it doesn't require the final to
>> be running in a linear mode. AM is inherently inefficient, but using a
>> Class A linear amp for the final wastes at least 75% of the electrical
>> power.
>
> If you have a tank circuit after the tube, you can run the tube in
> class AB, which has a higher efficacy.
>
>> Plate modulation only wastes half, which (if all you've got is
>> tubes) makes it a huge win.
>
> The final tube can run in class C, with a high efficiency, but the
> question is how to generate the high audio power. This has now been
> done for decades with semiconductors and some digital methods.
>
> For instance the Brown Boveri (now ABB) 500 kW HF or 600 kW MF
> transmitters from the 1980's used 32 floating power supplies in series
> feeding the plate. Depending of the instant audio waveform amplitude,
> 1-32 of these power supplies were actually activated, thus varying the
> plate voltage based on the audio waveform.
That's version of Class G, which will save some power, for sure.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by ●June 5, 20202020-06-05
On Fri, 5 Jun 2020 07:06:37 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 2020-06-04 21:03, John S wrote:
>> On 6/4/2020 3:14 PM, Phil Hobbs wrote:
>>> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>> wrote:
>>>>
>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>>> boomer#...@none.com wrote:
>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>> output?
>>>>>>
>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>>> tubes,
>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>> looking into other possible tubes.
>>>>>>
>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>>> but
>>>>>> after careful research, it's almost identical, but with a different
>>>>>> envelope (plate on the top cap).
>>>>>>
>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>>> from
>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>> RMS (per channel).
>>>>>
>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>>> but that is what was powering the amps. I owned two of them . We
>>>>> would use them for bass guitar or the PA.
>>>>
>>>> Megawatt AM modulators.
>>>>
>>>>
>>>>
>>>
>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
>>> of America) used a modulator tube to vary the B+ on the Class C final
>>> amplifer.� IIRC that improved the efficiency by about 2x compared with
>>> lower level modulation and linear amplification.
>>
>> IIRC, it was known as Heising modulation.
>
>I'd never heard the term, but a web search brings up screen-grid
>modulation examples, e.g.
><http://www.w8ji.com/Heising%20modulation.htm>.
>
>Plate modulation is different, because it doesn't require the final to
>be running in a linear mode. AM is inherently inefficient, but using a
>Class A linear amp for the final wastes at least 75% of the electrical
>power.
If you have a tank circuit after the tube, you can run the tube in
class AB, which has a higher efficacy.
>Plate modulation only wastes half, which (if all you've got is
>tubes) makes it a huge win.
The final tube can run in class C, with a high efficiency, but the
question is how to generate the high audio power. This has now been
done for decades with semiconductors and some digital methods.
For instance the Brown Boveri (now ABB) 500 kW HF or 600 kW MF
transmitters from the 1980's used 32 floating power supplies in series
feeding the plate. Depending of the instant audio waveform amplitude,
1-32 of these power supplies were actually activated, thus varying the
plate voltage based on the audio waveform.
Reply by ●June 5, 20202020-06-05
On Fri, 5 Jun 2020 06:58:34 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 2020-06-04 22:08, jlarkin@highlandsniptechnology.com wrote:
>> On Thu, 4 Jun 2020 16:18:35 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> On 2020-06-04 14:21, John Larkin wrote:
>>>> On Thu, 04 Jun 2020 19:39:05 +0300, upsidedown@downunder.com wrote:
>>>>
>>>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>>>> wrote:
>>>>>
>>>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5, boomer#...@none.com wrote:
>>>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>>>> output?
>>>>>>>
>>>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>>>> parallel. but I want more. I know it's possible to use eight 6L6 tubes,
>>>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>>>> looking into other possible tubes.
>>>>>>>
>>>>>>> At one time, I thought the 807 tube was more powerful than the 6L6, but
>>>>>>> after careful research, it's almost identical, but with a different
>>>>>>> envelope (plate on the top cap).
>>>>>>>
>>>>>>> I'm looking to get a full 500W RMS (or more) output (per channel), from
>>>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>>>> RMS (per channel).
>>>>>>
>>>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200 watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once looked up the RCA8000 and it was not listed as an audio output tube, but that is what was powering the amps. I owned two of them . We would use them for bass guitar or the PA.
>>>>>
>>>>> Search for some very old medium wave AM transmitters. These had
>>>>> essentially two signal paths, one for the RF carrier power and the
>>>>> other for the audio. These are combined in the huge modulation
>>>>> transformer (tens of kilowatts), so just replace the modulation
>>>>> transformer with an audio output transformer.
>>>>
>>>> The problem with the old transmitting jugs is that they need to run at
>>>> high plate voltages to make much power. Then the problem becomes,
>>>> where do you get the output transformer?
>>>>
>>>> Not to mention hundreds of watts of filament power.
>>>>
>>>> But a couple of 833As will impress your friends.
>>>>
>>>> https://www.dropbox.com/s/egadlyf5f8yo33z/833.jpg?raw=1
>>>>
>>>
>>> My last tube circuit (circa 1989) had an 833A in it--I needed to control
>>> some HV grids in a charge drift experiment, and nothing else had the
>>> combination of voltage capability and low off-state capacitance. I even
>>> ran the grid off batteries!
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> The Tek 519 scope was 1 GHz bandwidth, with no vertical amp and a
>> distributed-deflection crt. It used one giant 2cx-sort of tube for the
>> horizontal deflection drive. The scope was mainly used for photography
>> of rare single events.
>>
>> I have a tube.
>>
>> https://www.dropbox.com/s/r6c3zkwlqrayt53/519_CRT.JPG?raw=1
>>
>>
>>
>>
>I have no idea how they did that before JB Weld was introduced. ;)
>
>Cheers
>
>Phil Hobbs
I wonder how they turned all those setscrews. In a vacuum chamber?
Just TDR the stuff?
--
John Larkin Highland Technology, Inc
Science teaches us to doubt.
Claude Bernard
Reply by Michael Terrell●June 5, 20202020-06-05
On Friday, June 5, 2020 at 7:06:44 AM UTC-4, Phil Hobbs wrote:
> On 2020-06-04 21:03, John S wrote:
> > On 6/4/2020 3:14 PM, Phil Hobbs wrote:
> >> On 2020-06-04 12:23, jlarkin@highlandsniptechnology.com wrote:
> >>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
> >>> wrote:
> >>>
> >>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
> >>>> boomer#...@none.com wrote:
> >>>>> What is the most powerful audio output tube, as far as RMS wattage
> >>>>> output?
> >>>>>
> >>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
> >>>>> parallel. but I want more. I know it's possible to use eight 6L6
> >>>>> tubes,
> >>>>> which I believe is called " push-pull parallel - parallel", but I'm
> >>>>> looking into other possible tubes.
> >>>>>
> >>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
> >>>>> but
> >>>>> after careful research, it's almost identical, but with a different
> >>>>> envelope (plate on the top cap).
> >>>>>
> >>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
> >>>>> from
> >>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
> >>>>> RMS (per channel).
> >>>>
> >>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
> >>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
> >>>> looked up the RCA8000 and it was not listed as an audio output tube,
> >>>> but that is what was powering the amps. I owned two of them . We
> >>>> would use them for bass guitar or the PA.
> >>>
> >>> Megawatt AM modulators.
> >>>
> >>>
> >>>
> >>
> >> Yeah, big iron plate-modulated MF and HF AM transmitters (think Voice
> >> of America) used a modulator tube to vary the B+ on the Class C final
> >> amplifer. IIRC that improved the efficiency by about 2x compared with
> >> lower level modulation and linear amplification.
> >
> > IIRC, it was known as Heising modulation.
>
> I'd never heard the term, but a web search brings up screen-grid
> modulation examples, e.g.
> <http://www.w8ji.com/Heising%20modulation.htm>.
>
> Plate modulation is different, because it doesn't require the final to
> be running in a linear mode. AM is inherently inefficient, but using a
> Class A linear amp for the final wastes at least 75% of the electrical
> power. Plate modulation only wastes half, which (if all you've got is
> tubes) makes it a huge win.
The last known company for custom high power modulation transformers was Peter Dahl, which has gone out of business. With so many AM and SW transmitters being replaced with high efficiency solid state, their market dried up. Their main product was replacmets for broadcasters, and they could often supply a new transformer within three days. Their quality was higher than the originals, and flatter frequency response. One downside to the modern AM transmitters is the ability to modulate almost down to DC. A local station runs commercials that have <20 Hz content at a high enough level to mask most of the voices. You don't hear it on really cheap radios, but it sucks on a good radio.
Reply by Phil Hobbs●June 5, 20202020-06-05
On 2020-06-05 07:00, Gerhard Hoffmann wrote:
> Am 05.06.20 um 12:53 schrieb Phil Hobbs:
>> On 2020-06-05 06:35, Gerhard Hoffmann wrote:
>>> Am 04.06.20 um 22:14 schrieb Phil Hobbs:
>>>
>>>
>>>> Yeah, big iron plate-modulated MF and HF AM transmitters (think
>>>> Voice of America) used a modulator tube to vary the B+ on the Class
>>>> C final amplifer. IIRC that improved the efficiency by about 2x
>>>> compared with lower level modulation and linear amplification.
>>>>
>>>> They often used the same tube as the modulator and the final, which
>>>> makes perfect sense--the plate dissipation is very roughly the same,
>>>> and the RF isn't all that much faster than the audio.
>>>
>>> When I was still at school and a freshly licensed ham, I asked
>>> Thomson-CSF for a data sheet of a 2C39-like tube. They sent me in
>>> addition a complete data book of their product line, including the
>>> Hyper-Vapotrons intended for large MW transmitters.
>>>
>>> The Plate looked somehow like a hand granate, with the vapor that
>>> formed in the trenches shooting itself away from the tube.
>>
>> Pineapple or potato-masher? ;)
>
> pineapple
>
>>
>>> The data book may be still somewhere in my basement. :-)
>>
>> I'd be interested to see an English version if one exists.
>
> Short googling returned this:
>
> <
> https://www.sciencedirect.com/science/article/abs/pii/S0920379612003171
> >
Yikes, 30 MW/m**2? That's going some--like an SC-70 running at 120
watts, which could come in handy. ;)
30e6 W/m * (2 mm)**2 = 120W
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by Phil Hobbs●June 5, 20202020-06-05
On 2020-06-04 16:18, Phil Hobbs wrote:
> On 2020-06-04 14:21, John Larkin wrote:
>> On Thu, 04 Jun 2020 19:39:05 +0300, upsidedown@downunder.com wrote:
>>
>>> On Thu, 4 Jun 2020 08:31:56 -0700 (PDT), dragonworks1@comcast.net
>>> wrote:
>>>
>>>> On Thursday, December 8, 2016 at 10:20:51 AM UTC-5,
>>>> boomer#...@none.com wrote:
>>>>> What is the most powerful audio output tube, as far as RMS wattage
>>>>> output?
>>>>>
>>>>> I have gotten some powerful sound from four 6L6 tubes in push-pull
>>>>> parallel. but I want more. I know it's possible to use eight 6L6
>>>>> tubes,
>>>>> which I believe is called " push-pull parallel - parallel", but I'm
>>>>> looking into other possible tubes.
>>>>>
>>>>> At one time, I thought the 807 tube was more powerful than the 6L6,
>>>>> but
>>>>> after careful research, it's almost identical, but with a different
>>>>> envelope (plate on the top cap).
>>>>>
>>>>> I'm looking to get a full 500W RMS (or more) output (per channel),
>>>>> from
>>>>> all tubes, .... With four 6L6 tubes in PPP, I can only get around 120W
>>>>> RMS (per channel).
>>>>
>>>> I had MacIntosh MI2OO? amplifiers at one time. They deliverered 200
>>>> watts RMS out of two RCA8000 tubes. 940 volts to the plates. I once
>>>> looked up the RCA8000 and it was not listed as an audio output tube,
>>>> but that is what was powering the amps. I owned two of them . We
>>>> would use them for bass guitar or the PA.
>>>
>>> Search for some very old medium wave AM transmitters. These had
>>> essentially two signal paths, one for the RF carrier power and the
>>> other for the audio. These are combined in the huge modulation
>>> transformer (tens of kilowatts), so just replace the modulation
>>> transformer with an audio output transformer.
>>
>> The problem with the old transmitting jugs is that they need to run at
>> high plate voltages to make much power. Then the problem becomes,
>> where do you get the output transformer?
>>
>> Not to mention hundreds of watts of filament power.
>>
>> But a couple of 833As will impress your friends.
>>
>> https://www.dropbox.com/s/egadlyf5f8yo33z/833.jpg?raw=1
>>
>
> My last tube circuit (circa 1989) had an 833A in it--I needed to control
> some HV grids in a charge drift experiment, and nothing else had the
> combination of voltage capability and low off-state capacitance. I even
> ran the grid off batteries!
Misspoke. It was an 813A.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com