I'm interested in the thread topic
Wrenchone,
This thread got side-tracked, but I for one am very interested in the 18GB5 tubes and ways to put them to good use.
An author in "Tube Audio" tested 6GB5's some years ago and found that in triode (screen grid to plate) they performed like a super 6B4 with more power and less distortion. Since then I have been collecting them and now have a good supply to do something with.
Please keep the group informed about your experiments with the xxGB5's
Francois
Wrenchone,
This thread got side-tracked, but I for one am very interested in the 18GB5 tubes and ways to put them to good use.
An author in "Tube Audio" tested 6GB5's some years ago and found that in triode (screen grid to plate) they performed like a super 6B4 with more power and less distortion. Since then I have been collecting them and now have a good supply to do something with.
Please keep the group informed about your experiments with the xxGB5's
Francois
This is rather interesting. I just bought a bunch of 6S4S directly heated triodes (Russian version of 6B4G), with the idea of using them in a P-P class AB2 amplifier. It would amuse me to no end that triode-connected cheap sweep tubes would be the equal of these. I always cringe at using directly heated tubes in such an application due to all the extra opportunities for noise injection.
Go directly to the 6AV5GA, do not pass go, do not collect $200........
There used to be a story about some multi grid indirectly heated 6B4G tubes being sold on Ebay. I dismissed it as an urban legend until I found one of the tubes. Upon investigation I uncovered a much bigger story.
It seems that some tube makers had contracts to fulfil as their tube production was winding down and production lines were being shut down. The manufacturers worked with the contract holders to find creative solutions to fill orders. This lead to some rather unusual glass stuffing. The manufacturers found something on hand that would work in the contract holders design and built tubes for them only. These tubes have now found their way into the surplus market. Phillips EGC and Sylvania were the biggest players here.
This led to the famous 7027A guts inside the 6BG6GA bottle (sold by SND sales as the "super 6BG6"). It also led to some triode wired 6AV5GA's stuffed inside 6B4G bottles. I have also found some wimpy RF tubes labled 6CW5's and they melt at normal 6CW5 levels.
The folklore went on to say that the 6AV5GA was a direct replacement for the 6B4G. This is obviously not true, it only means that the substitution worked in the contract holders circuit, which could have been a power supply for all we know.
I compared the 6B4G and the 6AV5GA in a Tubelab SE several years ago. That story is here:
6AV5GA testing
Here are some plate curve sets for 13GB5. All curves are 50 mA/div Vert. and 50V/div. Horiz.
By the way, 13GB5 is nearly identical to 21HB5 for plate curves. (another $1 tube back when, but 12 pin Compactron)
1) 13GB5 pentode, 130 Vg2, 2 Vsteps on g1
2) 13GB5 triode, 7 Vsteps on g1
3) 13GB5 g2 drive, 110 V max Vg2, 7 Vsteps on g2
4) 13GB5 Crazy/Twin drive, 75V max Vg2, 7 Vsteps on g2
By the way, 13GB5 is nearly identical to 21HB5 for plate curves. (another $1 tube back when, but 12 pin Compactron)
1) 13GB5 pentode, 130 Vg2, 2 Vsteps on g1
2) 13GB5 triode, 7 Vsteps on g1
3) 13GB5 g2 drive, 110 V max Vg2, 7 Vsteps on g2
4) 13GB5 Crazy/Twin drive, 75V max Vg2, 7 Vsteps on g2
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I just returned from a vacation in Florida that passed through Orlando. Now most people would go visit one of the popular tourist traps where you stand in a line for an hour in the hot sun to stuff yourself along with several others into a thrill ride that lasts maybe two minutes.....been there done that......Not this time.
Sherri and I went to visit a much lesser known attraction....ESRC, home of the $1 tube list. Here I discovered that the XXGB5's and XX500's are virtually extinct. The story is familiar....... Asian buyer grabbing up every available tube that makes print on this and a few other audio forums, with a new twist......The buyer is in the USA and he has an amp design that uses the 6GB5, 13GB5, or 18GB5. He has yet to sell the first amp, possibly something to do with funding, and Stan has sold him 40,000 XXGB5's over the past 4 years.
Apparently this buyer would only accept Mullard made (regardless of the brand on the tube) for the first 3 years, but lately has started accepting Certain Japanese made tubes. Stan will not sell me ANY XXGB5's, not even the Korean made firecrackers that a few of us have blown up.
I too have a nice amp designed for these tubes, but it seems that they will be extinct sooner than expected, so the design will be scrapped. I spent several hours discussing possible alternatives with Stan, and checking inventory. I left ESRC with 270 tubes.....and NO I will not mention any numbers. I will trade all my remaining 13GB5's for whatever I need for my next design.
I have two nice amp designs that would have been the next two Tubelab products, except that you can't get any tubes for them. The 6HB6's DID all go to Hong Kong.
There is a real possibility that the next Tubelab product won't be an amp, and won't contain any tubes......but tube stuff is coming. If the current trend continues, we will all be stuck designing equipment with current production tubes, which severely limits creativity. There are no current production sweep tubes.
Sherri and I went to visit a much lesser known attraction....ESRC, home of the $1 tube list. Here I discovered that the XXGB5's and XX500's are virtually extinct. The story is familiar....... Asian buyer grabbing up every available tube that makes print on this and a few other audio forums, with a new twist......The buyer is in the USA and he has an amp design that uses the 6GB5, 13GB5, or 18GB5. He has yet to sell the first amp, possibly something to do with funding, and Stan has sold him 40,000 XXGB5's over the past 4 years.
Apparently this buyer would only accept Mullard made (regardless of the brand on the tube) for the first 3 years, but lately has started accepting Certain Japanese made tubes. Stan will not sell me ANY XXGB5's, not even the Korean made firecrackers that a few of us have blown up.
I too have a nice amp designed for these tubes, but it seems that they will be extinct sooner than expected, so the design will be scrapped. I spent several hours discussing possible alternatives with Stan, and checking inventory. I left ESRC with 270 tubes.....and NO I will not mention any numbers. I will trade all my remaining 13GB5's for whatever I need for my next design.
I have two nice amp designs that would have been the next two Tubelab products, except that you can't get any tubes for them. The 6HB6's DID all go to Hong Kong.
There is a real possibility that the next Tubelab product won't be an amp, and won't contain any tubes......but tube stuff is coming. If the current trend continues, we will all be stuck designing equipment with current production tubes, which severely limits creativity. There are no current production sweep tubes.
Again!!! 40,000!! Sheeeeeeeeit! 
USA huh. 13/xGB5 would be near drop in replacements for 21JV6 (a 21HB5 look-alike), used in a certain switching OT amplifier. I kind of had the impression that that only sold a few dozen amps a year at best. Maybe something else?
Where would they get 40,000 Magnoval sockets? And the weird plate caps. The caps I have seen won't even stay on them.
Low cost TV Sweeps are getting fairly sparse. I'm not going to mention any cheap ones any more.
USA huh. 13/xGB5 would be near drop in replacements for 21JV6 (a 21HB5 look-alike), used in a certain switching OT amplifier. I kind of had the impression that that only sold a few dozen amps a year at best. Maybe something else?
Where would they get 40,000 Magnoval sockets? And the weird plate caps. The caps I have seen won't even stay on them.
Low cost TV Sweeps are getting fairly sparse. I'm not going to mention any cheap ones any more.
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I have a box full of old plate caps from the 1960's. They were made before the 6GB5 came out. They fit the 6BQ6 and 6DQ6 but work fine on the 13GB5's. I haven't tried the usual white ceramic Chinese caps, but most of them need a good squeeze with pliers before use anyway.
For sockets, I use the Chinese sockets made for the tubes with 0.040 inch pins. Just jam an .050 inch tube in there once and it fits OK for hundreds of insertions. Just don't plan on ever using an .040 tube in there again.
The Russians sell a reasonably nice ceramic socket meant for Magnoval tubes, definitely a touch better than the usual Far East products. The only caveat would be to use some plastic washers when mounting the sockets, as the mounting ears are ceramic.
I also have some PC mount ceramic sockets of unknown origin that seem to handle the Magnovals just fine without forceful persuasion. I think those were an Ebay buy out of England.
I also have some PC mount ceramic sockets of unknown origin that seem to handle the Magnovals just fine without forceful persuasion. I think those were an Ebay buy out of England.
That's a shame, but I understand. I for one enjoy your forays into uncharted territory.
jeff
With 40,000 tubes, someone must have dreams of selling tube Amps at WalMart or BestBuy. I'm surprised that such large quantities of any tube exist.
They couldn't leave a few hundred tubes for the hobbyists? George, maybe you should mail order sell the last ones you have in small quantities.
It might be safer to design tube kits around tubes that are only modestly abundant. Although 6JN6 and 6GV5 sold out pretty fast for the big red board.
They couldn't leave a few hundred tubes for the hobbyists? George, maybe you should mail order sell the last ones you have in small quantities.
It might be safer to design tube kits around tubes that are only modestly abundant. Although 6JN6 and 6GV5 sold out pretty fast for the big red board.
As far as contacts for the small plate caps, I mentioned a few years ago using fuse clips - the thread is here...
http://www.diyaudio.com/forums/tubes-valves/166703-fuse-clip-small-plate-cap-use.html
http://www.diyaudio.com/forums/tubes-valves/166703-fuse-clip-small-plate-cap-use.html
It's difficult to see how an amp using tubes with anode caps could easily be built to pass safety standards, still be visually appealing(other than to the denizens of this forum) and thus viable on a large commercial scale. I would say that whoever has bought these is living in a dream world. I suppose that the highest filament voltage tubes ones will remain available for some time.