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Old 21st September 2009, 06:34 PM   #1
dogfish is offline dogfish  United States
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Default Simple SE with 807?

I bought an 807 tube at a flea market this weekend. It was love at first sight -- it's a beautiful tube.

On doing some research, I see the 807 is somewhere between a 6L6 and a 6L6GC, closer to the latter. Has anyone tried wiring up a converter socket (a la the converter for the "super" 6BG6 http://www.vacuumtubes.com/6BG6.html) so it can be used in an octal socket? Has anyone tried an 807 in a Simple SE?

The thought of being able to try NOS 807s for $10-15 each (rather than $50+ each for NOS EL-34s) in my Simple SE is very appealing.
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Old 21st September 2009, 06:50 PM   #2
bigwill is offline bigwill  United Kingdom
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Other than the socket issue I see no reason why it wouldn't work - a lot of 807s have 6L6 innards. The top-cap allows a higher maximum plate voltage than a normal 6L6 because octal sockets have issues with arcing!
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Old 21st September 2009, 07:10 PM   #3
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Quote:
I see the 807 is somewhere between a 6L6 and a 6L6GC, closer to the latter.
No it is actually closer to the former. Most surplus 807's come from the WWII and post war era and they were made with 6L6GA or 6L6GB innards. The maximum screen grid voltage rating for an 807 is 300 volts. The maximum for most 6L6GA, or GB is between 325 and 360 volts depending on which book you read. Either way they don't work at 400 volts.

Most Simple SE's run the B+ well over 400 volts which will make life pretty unhappy for an 807. I played with some 807's and 1625's during the development of the Simple SE and found that most of them will not handle 435 volts at all. There are a few later vintage 807's that are probably made with 6L6GC innards and they will work well. These are fairly uncommon and hard to identify.

There have been a few Simple SE's built with lower voltage transformers that will work with the 6L6G. These will work with the 807 but the power output is a bit lower. I built one with a surplus transformer that has a B+ of 355 volts, but I am currently running trioded 6V6's in it. Two very nice sounding watts per channel.
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Old 21st September 2009, 07:33 PM   #4
dogfish is offline dogfish  United States
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Quote:
Originally Posted by tubelab.com View Post
[...] The maximum [...] is between 325 and 360 volts depending on which book you read. Either way they don't work at 400 volts.

Most Simple SE's run the B+ well over 400 volts which will make life pretty unhappy for an 807. [...]
Thank you, George.

That's too bad. They are very pretty tubes, and I am very happy with my Simple SE. I guess I'll have to come up with some other bottom-feeder way to play with NOS tubes.

Maybe I'll try out the super-6BG6 hack from vacuumtubes.com...

And thanks again for making it all possible for me and so many others!
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Old 21st September 2009, 07:35 PM   #5
bigwill is offline bigwill  United Kingdom
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Originally Posted by dogfish View Post
Thank you, George.
That's too bad. They are very pretty tubes, and I am very happy with my Simple SE. I guess I'll have to come up with some other bottom-feeder way to play with NOS tubes.
Why not try pentode mode? It's not evil....
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Old 21st September 2009, 07:36 PM   #6
dogfish is offline dogfish  United States
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I don't understand -- run the Simple SE in pentode mode? The 807?
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Old 21st September 2009, 07:42 PM   #7
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What you'll need is a lower (fixed) screen voltage - a dropping resistor plus filter capacitor is simplest, but regulating it with zeners or gas tubes will be better. Pentode mode has a high output impedance, so a bit of negative feedback is helpful.
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Old 21st September 2009, 08:14 PM   #8
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Consider the RH807 as a good home for the 807. I built two versions and they both sounded good. Place a decent pentode up front rather than the ECC81 and you should have a giant killer. This will be good for about 6watts in SE pentode mode.

Shoog
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Old 21st September 2009, 11:59 PM   #9
llwhtt is offline llwhtt  United States
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Default Se807

Gordon Rankin wrote a DIY article about a SE807 amplifier in the one of the early Sound Practice issues. All of the Sound Practice issues are downloadable for free if you look hard enough. He even got Mike at Magnequest to wind the OPT, they are probably still available. Mike used the same size core as a Dynaco 451, it was huge to say the least.

Craig
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Old 22nd September 2009, 11:37 AM   #10
mus is offline mus  Canada
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Quote:
Originally Posted by Shoog View Post
Consider the RH807 as a good home for the 807. I built two versions and they both sounded good. Place a decent pentode up front rather than the ECC81 and you should have a giant killer. This will be good for about 6watts in SE pentode mode.

Shoog
Hi Shoog,
Can you describe more how you wired up your pentode driver for your RH807? A schematic will be nice.
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