thanks, after i posted, i remembered that MilesPrower posted how to get those off plate curves....i will try to use your curves to get those...
one more question, what brand did you take those from?
and what do you think about paralleling them to get 2A3 OP's?
That particular tube was a Raytheon. Most of the tubes I have are Sylvania, RCA and GE however. I'll trace some of those tomorrow to compare, but I know they are quite similar. I have run into a Triad version that is very different, looks similar but 1/2 the gm and obviously not frame grid design.
2A3 is a very different tube, with a Mu of 4.2 versus 30 or so here. Paralleling won't change the Mu. The 2A3 Rp of 800 Ohms could be easily met by paralleling 2 of the tubes (in triode). But these tubes have 4x the gm per tube of the 2A3.
Four or five of these in parallel would make for an 8417 on steroids, with 100,000+ gm. Almost a Mosfet.
2A3 is a very different tube, with a Mu of 4.2 versus 30 or so here. Paralleling won't change the Mu. The 2A3 Rp of 800 Ohms could be easily met by paralleling 2 of the tubes (in triode). But these tubes have 4x the gm per tube of the 2A3.
Four or five of these in parallel would make for an 8417 on steroids, with 100,000+ gm. Almost a Mosfet.
I found two new in boxes in my oddball tube stash. The boxes are "Realistic Lifetime Tube".
The two are different makes though. One has a medium halo getter and grey plates, it says Japan on it.
The other one has a large halo getter and black plates, I think it's a Sylvania or maybe Raytheon.
Cool tubes
I would post pictures but don't want to tip off anyone out of the loop.
The two are different makes though. One has a medium halo getter and grey plates, it says Japan on it.
The other one has a large halo getter and black plates, I think it's a Sylvania or maybe Raytheon.
Cool tubes
I would post pictures but don't want to tip off anyone out of the loop.
thanks again....mu of 30 means lower grid voltage and lower drive requirements...
i mentioned the 2A3 because i recently made a parallel 4P1L SET to mimic the 2A3 operating point...paralleling the 4P1L is a breeze....so i wonder how these tubes from hell will stack up wrt to paralleling...
you are right, my bad, i was thinking gm and not mu.....
i have 6mn8's to try....http://www.nj7p.org/Tubes/PDFs/Frank/123-GE/6MN8.pdf
i have 6mn8's to try....http://www.nj7p.org/Tubes/PDFs/Frank/123-GE/6MN8.pdf
Yep, paralleling these high gm tubes may be a significant challenge. I wouldn't assume that it's readily do-able at this point. That other earlier thread, where someone suggested using them in parallel for outputs, never concluded with any results. They may have given up. In any case, I'm sure there will be some ferrite beads, RF bypass caps, and grid stopper resistors needed.
The tubes are rated for 0V grid1 positive on the datasheet, so that's another issue for a practical amp. Some clamp diode may be necessary to avoid poofing tiny frame grid wires.
Paralleled tubes often have current sharing issues, which can lead to oscillations with so much gm. So matching and some HF degeneration will be needed. You will need a scope for sure to parallel these things. The one hope is that frame grids should at least be fairly uniform, just the usual centering issues in the mica supports.
And then they may be quite microphonic too. Very close spacing between grid and cathode will be sensitive. The stiff frame grid supports may give some relief, but they better be tight in the mica insulators. How many times have these tubes been shipped in a truck over bumpy roads? I'm not sure these $1 things have been tested either. And I don't think they give you the choice of brand at $1.
If they were easy to use, they would have caught on long ago, and would NEVER have ended up on the $1 list. They might really BE the "tubes from Hell". Some experimenting and refinement of techniques will be forthcoming on the learning curve. I'm sure some solution can be found. The question is whether a solid recipe can be developed, that will not be too sensitive to wire layout. So allowing parallel (or even single) use without a HF scope as a requirement.
The tubes are rated for 0V grid1 positive on the datasheet, so that's another issue for a practical amp. Some clamp diode may be necessary to avoid poofing tiny frame grid wires.
Paralleled tubes often have current sharing issues, which can lead to oscillations with so much gm. So matching and some HF degeneration will be needed. You will need a scope for sure to parallel these things. The one hope is that frame grids should at least be fairly uniform, just the usual centering issues in the mica supports.
And then they may be quite microphonic too. Very close spacing between grid and cathode will be sensitive. The stiff frame grid supports may give some relief, but they better be tight in the mica insulators. How many times have these tubes been shipped in a truck over bumpy roads? I'm not sure these $1 things have been tested either. And I don't think they give you the choice of brand at $1.
If they were easy to use, they would have caught on long ago, and would NEVER have ended up on the $1 list. They might really BE the "tubes from Hell". Some experimenting and refinement of techniques will be forthcoming on the learning curve. I'm sure some solution can be found. The question is whether a solid recipe can be developed, that will not be too sensitive to wire layout. So allowing parallel (or even single) use without a HF scope as a requirement.
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Hmmm. Now I was curious. May have to ask for a PM, if still have time for ...
The last description of smoking-amp reminds me the 6HB6 (for vertical output): high gm and high mu; It must be of the same age / generation ... but I can not guess what ....
The last description of smoking-amp reminds me the 6HB6 (for vertical output): high gm and high mu; It must be of the same age / generation ... but I can not guess what ....
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I think you mean the 6HB6, a vertical sweep high gm tube. (6HB5 was a typical Horiz. Sweep tube). The 6HB6 used a conventional (non-frame), but tightly wound, grid1. It was more variable in characteristics than typical non frame grid tubes. We don't yet have a good dataset on these new tubes from H to really say yet. But I would expect the same issues with paralleling the 6HB6 as with these.
Perfect, I corrected the code in the post #173 (I forget the code and associated it with 6EM5, 6AQ5, etc... and I write 6HB5)
I remember the 6HB6 thread, this tube has very bad matching...
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I have played with them, but never tried parallel operation. I stuffed them into Pete's driver board and they work about the same as the 6HB6 in that board. I have a BIG bunch of 6HB6 so that's what went into the board.
On a positive note, I test either tube type in the curve tracer here with 10 inch leads, using grid stopper resistors (1K for g1, 120 Ohm for g2) and some ferrite beads on the grid leads near the pins, without any oscillation issues. So they CAN be tamed.
I haven't tried parallel Op yet either though.
Some generational info:
The tube from H was designed by Sylvania in 1966. The 6HB6 was designed by Raytheon in 1961.
The 12BY7 was designed by CBS in 1951. Later upgraded to the 12BY7A by GE in 1954 (controlled warmup).
I haven't tried parallel Op yet either though.
Some generational info:
The tube from H was designed by Sylvania in 1966. The 6HB6 was designed by Raytheon in 1961.
The 12BY7 was designed by CBS in 1951. Later upgraded to the 12BY7A by GE in 1954 (controlled warmup).
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No, I think it was a really bad week for silicon, and one poor tube.
I ripped all the important stuff off the wrong side of the test boards, and stuffed them on the proper side. I left the tube sockets, and just soldered a second socket to the other side of the board. It looks kinda funny with a socket on both sides, but it works.
The board is a "Swiss army knife" kind of breadboard, it has (or does) a bit of everything. So today I configured it for a pair of those "worthless" regulator beam triodes. These things make the mystery tube pale and hide....Mu 300, Gm 55,000 Plate dissipation rated for 30 watts, but I haven't made one glow yet. The problem, you need positive G1 for any plate voltage less than about 750 volts. Not a problem with this breadboard. Direct coupling a high Gm mosfet to a high Gm tube.......BIG PROBLEM. I have a pile of dead mosfets.....TV sets and radios were going bonkers, and we are on cable.
Stopper resistors and magic beads everywhere, I finally tamed the TV jammer, but never could get big watts at reasonable distortion, so.....game over. Time to move on.
I will reconfigure the boards for something more realistic, like a regular old sweep tube with drive going into G1. I only have a few 6GE5's at hand (I know there's more in a box somewhere) so I will stick something else in there for initial testing....just in case I wire B+ to G1 again.
I have mowing duty at the church tomorrow, so it may be the weekend before I get back to this stuff.
PM sent.
Re: Chris H
"What was it that folks called a one-tube one-Watt amplifier? (besides QRP - that was the old days)."
There are quite a few dual tubes that might fit that description.
On the $1 lists there are/were a few that could be used.
(there was a Vacuumtubes.net $1 list earlier too)
Some $1 candidates:
6AG9 6AH9 6LU8 8AL9 6HZ8 6FY7 15FY7 6FJ7 13FM7 13GF7 16LU8 21LU8 21LR8 31LR8 10DR7 13DR7 6CM7 8CS7 6JZ8 13/17/24JZ8 then a bunch of 9DX base tubes like 6LY8 6LQ8 6KR8 6JT8 6LB8
some others not on $1 list: 6BM8 6LR8 6MY8 6GF7 6EM7 6EW7 6FD7 6DN7 6DE7 6EA7 6FM7 6GL7 6CS7
6AH9 contains the "tube from H" as one section.
Re: Chris H
"What was it that folks called a one-tube one-Watt amplifier? (besides QRP - that was the old days)."
There are quite a few dual tubes that might fit that description.
On the $1 lists there are/were a few that could be used.
(there was a Vacuumtubes.net $1 list earlier too)
Some $1 candidates:
6AG9 6AH9 6LU8 8AL9 6HZ8 6FY7 15FY7 6FJ7 13FM7 13GF7 16LU8 21LU8 21LR8 31LR8 10DR7 13DR7 6CM7 8CS7 6JZ8 13/17/24JZ8 then a bunch of 9DX base tubes like 6LY8 6LQ8 6KR8 6JT8 6LB8
some others not on $1 list: 6BM8 6LR8 6MY8 6GF7 6EM7 6EW7 6FD7 6DN7 6DE7 6EA7 6FM7 6GL7 6CS7
6AH9 contains the "tube from H" as one section.
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