^i have all the irons on hand, the chassis is in the powder coating shop....
i am using an 11HM7/6GU7 combo and 2SK3563 mosfet folowers.....operting point will be as per datasheet...
will use regulated screen grid supplies using IRF840 mosfets and zener references...
like my previous builds, power supply filtering will have generous amounts of filter caps given that they are dirt cheap in my country, they were taken from computer power supplies.....
post some pics when the parts arrive
.@tubelab ... You are not an 2A3 fan, I see
)
I am not a fan of any high dollar tubes. I have only tried low $$$ 300B's and 2A3's but I have never been able to get a sound that I like out of the Chinese, Russian, or RCA twin plate 2A3's. Those are the only ones that I have. I get better sound from low $$$ 300B's (Sovtek and Shuguang).
I really like the 45's and was fortunate enough to collect a few before they got expensive. I won an auction on Ebay once that included 3 45's and a few other tubes for $15 total. Yes it was a long time ago.
I have heard a few nice sounding 2A3 amps playing through Lowther horns. We hooked up a Tubelab SE running some really old (1929) NX-483 tubes and I (and a few others) thought it sounded better. I might have a biased opinion though.
This is a 3KW audio amplifier build by a friend in order to Plate modulate a pair of 4-1000A. The phase splitting was made by a UTC A10 interstage, then a pair of 12BY7's as anode followers and in the final stage a pp pair of 4cx1500b's at 3500Volts. The modulation transformer weight about 80Kgr. Interesting eehh??
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Considering the fact that you have played with alot of tubes, high voltage tubes....i would like to ask you if you have been able to notice any major difrences between low voltage, high current tubes, and high voltage, low current tubes.
This is a 3KW audio amplifier build by a friend in order to Plate modulate a pair of 4-1000A. The phase splitting was made by a UTC A10 interstage, then a pair of 12BY7's as anode followers and in the final stage a pp pair of 4cx1500b's at 3500Volts. The modulation transformer weight about 80Kgr. Interesting eehh??
OMG!
An externally hosted image should be here but it was not working when we last tested it.
This was a project that I started about 10 years ago. I'm not sure how much power it makes but it is at least 500 watts. On the 10x probe the waveforms were going off-screen on my scope that I was using at the time to view the waveform. Its an OTL, and makes its greatest output power into about a 3 ohm load. You can test the power tubes on the fly. It has a built-in AC line voltage regulator, so if the line sags to 100V it will still make full power. There are plenty of meters, you can see the line voltage, the corrected line voltage, the output of the amp, any DC it may have and also the results from the tube tester. The whole amp is wired point to point. Bias and DC offset (the output of the amp is direct-coupled) are automatic.
This is a 3KW audio amplifier build by a friend in order to Plate modulate a pair of 4-1000A. The phase splitting was made by a UTC A10 interstage, then a pair of 12BY7's as anode followers and in the final stage a pp pair of 4cx1500b's at 3500Volts. The modulation transformer weight about 80Kgr. Interesting eehh??
Hi Satelitis !
Here is some older pictures of my friend - chika Dule ( Yu1 ) - MW ( Midlle Wave 1,6 -1,8 MHz ) pirate DIY tube transmitter equipment :
Modulator ( B-class AF amplifier ) consist from four Russian GU81M power tubes , running at 3,5KV UBa , there on that chassis is some other smaller AF input/driver tubes to .
Transmitter output power tube is some Russian middle power coaxial ceramic tetrode running in C class , plate /G2 modulation , with scaling UBa from 4 up to 7,5KV , producing up to 5KW of pure carrier signal power , driver tube is GK71 , buffer tube is GU50 , and basic VFO oscillator is EL84 tube .
Inside of this small radio pirate studio neon light tubes lighting without to be wired , started to light being excited from transmitter huge electromagnetic field .
This tube transmitter signal and program is heard loud and clear on Japan ,which distance is about 12ooo miles far away .
Best Regards !
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You have been saying this since "Sound Practices" days... How is the project coming along? Getting the OPT with acceptable frequency response and HV insulation adequate for the task will be the trick.
I had four of these 851 tubes and several 849 tubes in my closet for 20+ years, wanting to do the same thing as you want to, but I came to my senses and realized that I would never get around to it. I hope you have more perseverance with your project than I did. The plate resistance values are nice with the 851 but the 304TL has an even lower plate resistance and can output nice power with a B+ of less than 1000 volts. The 304TL's 5 volt filament is also much better for AC filament supplies than the 851's 11 volt filament, but I guess it doesn't matter if well regulated DC is used on the filament. I've always liked AC though.
I just finished this one (18.5 kg before potting) for an 851....
The tube next to the transformer is an 845, to give an idea of dimension.
I am happy that the customer listens in mono
Left in the picture is a 211; at the right an 851.
Wow! Nice work. That transformer looks super well built. It looks like you are the one that bought the 3 new 851 tubes on Ebay several years ago.
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