807s?

[Charlie Bernstein]

The Weber Lauren amp kit's output tube is an 807. I've never heard of them and can't find any descriptions online. What do you know? Clean? Dirty? Smooth? Crunchy? Crisp? Fat? Bright? Dark? Do they go by any other names?

Thanks!

[Steve Conner]

The 807 is a pre-WW2 vintage tube designed as a RF power amp. Very similar to a 6L6, except for the different base and the top cap. Probably sounds similar to one, too.

They're almost never used in audio amps. Almost.

The Champ CBA-20807 1000 Watt Amplifier - Part 2

[Jazz P Bass]

http://www.mif.pg.gda.pl/homepages/f...41/g/GL807.pdf
807 datasheet link.

[Charlie Bernstein]

Thanks! The Lauren sounds like a fun beginner kit. Wonder why they don't just use a 6L6. Maybe there was an 807 fire sale? Or five pins is easier for novices to deal with? Think I'll email them and ask.

=O.

[Charlie Bernstein]

PS to Steve - I love the 1,000-watt monster! Is it for playing old LPs in the privacy of your three-room flat? Have you considered replacing the blue LEDs with grow-lights?

[Steve Conner]

It's not mine! It was made by John Chambers in Nottingham. I've yet to play a gig where I could use more than about 60w.

807s are cheap compared to the usual audiophile approved tubes, because they won't fit off-the-shelf tube amps without some serious modifications. Weber always had a good eye for a bargain.

[redelephant]

Hmmm...My understanding is 807s are more popular among DIY HiFi freaks than 6L6s. I think it's partly because of the bottle shape, and the top cap make em look cooler. I've seen quite a few AB2 circuits using 807s and wonder if they perhaps have sturdier grids that handle more grid current compared to 6L6s?
The construction with the top cap also gives it higher voltage rating.

[km6xz]

Some class B theater systems used 807's in the 40s and a couple of organ amps used them but they have never been known for great AF performance, being designed specifically for RF. They were popular with DIY projects after WWII because millions were available surplus for as little as 20 for a dollar. Later they were advertised in electronics hobby magazines such as Popular Electronics and Electronics Illustrated in the 50s for $0.25 each. I built several RF projects with them when 11-14 y.o.. They were the tubes used in the famous Command Sets, ARC-5 transmitters used in many of the fighter aircraft of US Army Air Corps, before the Air Force was created as a separate branch. They are not octal based so sockets are not as common nowadays In Class C RF use we were getting 60-90 watts out on one tube. We never pushed tubes too much, unlike in guitar amps, because adding tubes or using bigger tubes was an option since there are more good RF tubes with moderate and high anode dissipation than AF type tubes. One RF tube that really translated well into AF class AB operation from my experience was the 3CX300 series with 300 watts of CCS dissipation a tube half the size of a 6550. I've built several amps in different configurations that performed well, and coasted at 300++ watts out and would not expect to need replacements for many years. Here in Russia there was the original version called a GM-5 that had a cathode tied to the heater. Same specs otherwise and socket, but $10 versus $80 wholesale for the 3CX300. In fact, Svetlana has dropped its production because no manufacturers adopted it for AF power amps. I designed one for a high end hi-fi company which sold only a 1/2 dozen sets of mono blocks but their selling price of $40,000 limited its appeal.
The year before I designed a 833A glass tube Class A amp for them. It was very impressive looking. 833A were designed as AM plate modulators and long or middle wave RF broadcast. They wanted $45,000 for a pair and sold only a few. I did it as an attention getter as they claimed they wanted. It was for an international hi-fi show and I was specific in detailing to them that it was not for production, the design was not safe from curious fingers getting too close to the grill stainless steel rolled tubing cage that exposed the tube, mounted horizontally. They took orders anyway. The next show I created one that was liquid cooled and all the outputs and driver circuits and tubes were submerged in a clear Pyrex column filled with clear transformer oil. I made a few versions for M.I. just to play with. It was a lot lighter than a SVT but more power with much longer tube life.
Another triode that was designed for audio and in the 160 watt range is the 812, the more linear low frequency version of the popular 811a which, a quad in class C RF application produced 800 watts, and not much larger than a 6550. A more modern version is the 572B, which sells for about $40. A couple of Altec amps used 811a's/812's with good results.
The biggest tube AF amp use for speaker drive I ever saw close up in operation was one with 2 Eimac 4-1000A transmitting Tetrodes. Their only real limitation was they needed 2 120cfm blower cooling their glass cooling chimneys..oh, and the 200++ lb output transformer. That was 2000 watts of anode dissipation out of two tubes and 3,500 watts RMS output with 4200 plate volts. Their 7.5 volt heaters consume 42 amps for two.
I am waiting for some well funded bass player to contract for me to build one, that would be fun.
I've seen much larger AM modulators, in the 50,000 watt range but those are no substitute for a speaker driving amp.
A high Z speaker array for a PA