As some of you already know I designed a PCB for a 50 watt monoblock version of the "Engineer's Amp". It uses 6HJ5 tubes, B+ of about 410V, and does an easy 50 watts out into 8 ohms.
You can see the details on my web site: Engineer's amp 50W monoblock
I have one assembled into a chassis now. I will be doing more measurements soon. It works very well 🙂
Pete
I hope there's more of those tubes left. George and friends might have burned up a few working on those 100 Watt and up earth shakers.
21LG6, 17KV6 and 26DQ5 are fairly similar tubes except for pinout and socket. Might be useful to allow for some pinout re-assignments and optional plate caps. And then there's bigger TV tubes.... 1/2 KW dreams-obsessions
21LG6, 17KV6 and 26DQ5 are fairly similar tubes except for pinout and socket. Might be useful to allow for some pinout re-assignments and optional plate caps. And then there's bigger TV tubes.... 1/2 KW dreams-obsessions
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yeah, but you get the really cool accents and great words like bum.
There is a Hammond 291FX upgrade xfmr ($114) for the presently specified 290FX ($92). It's more expensive, but has 29M6 laminations for quieter running.
I assume the rather more expensive 300 series (373FX, $182)) has M6 laminations too. Weighs 1.5X as much. Must run at lower flux density.
The EDCOR XPWR247 looks like the only similar XFMR, but only rated 325 mA (versus 450 mA for 290FX) and it doesn't have enough current for the 6.3 VAC heaters.
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"the incredible unfairness of living on the bum of the world."
As long as Atlas doesn't take a break, you should be fine.
I assume the rather more expensive 300 series (373FX, $182)) has M6 laminations too. Weighs 1.5X as much. Must run at lower flux density.
The EDCOR XPWR247 looks like the only similar XFMR, but only rated 325 mA (versus 450 mA for 290FX) and it doesn't have enough current for the 6.3 VAC heaters.
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"the incredible unfairness of living on the bum of the world."
As long as Atlas doesn't take a break, you should be fine.
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for some reason i could not get his boards, still having fun with point to point wiring...
i use 0.35mm H18 and rm18 taiwan laminations for power traffos that
i use in my tube amp builds....
i use 0.35mm H18 and rm18 taiwan laminations for power traffos that
i use in my tube amp builds....
?
Looking.....
Still looking.....
It is not clear if there is or there is not pcb's for sale but on web site there is notice (somewhere) that pcb's "will" be on sale on ebay.
I don't remember blowing up a single 6HJ5 although I did find a few that were bad out of the box. They were gassy, some glowed (they were trashed), others had the creeping bias current syndrome that will eventually lead to runaway. Some of these may usable in an amp with a mosfet driving the grid, so they were marked and saved......somewhere.....maybe.
I moved all of my stuff twice before settling into this place. We had to leave Florida on 3 weeks notice, so what was an organized move turned into utter chaos, and I'm still looking for parts of projects that were planned, or in progress when the chaos hit. The worse part is finding most of a project, but the key bits are still missing after over two years. I found all the parts for a guitar that I was building except the neck......It shouldn't be too hard to find a guitar neck, but it's still missing.
While looking through an unmarked box for something else, I found Big Red #1, the original experiment. Two other boards were built, one was left in Florida, the other is part of another stalled project. Number 1, looks complete except for the missing input tubes, but the original 6HJ5's are still there.
Attachments
I've got several Dynaco MKIII's hanging around. I wonder how well these OPT's would work in this design? Primary impedance seems to be the same.
I checked with one vendor - RES (Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!) - and they have 500+ 6HJ5 tubes, and literally thousands of 6GU5 tubes. And that is just one vendor. I don't think we will run out of them...
Pete
I know, I am being conservative... but it seems like many people are a risk building these things. I don't want any electrocutions, or fires...
Pete
Perhaps. But the plate current doesn't vary that much with +/-20% AC line voltage. Current does increase at lower line voltage, but since unregulated plate voltage drops, plate dissipation stays about the same.
Pete
"and they have 500+ 6HJ5 tubes, and literally thousands of 6GU5 tubes"
That's excellent, everyone should own at least one low cost TV Sweep tube amp. Something of a "standard candle" if you will. ( Well, owners of multiple extremely expensive "audiophile" amplifiers probably should not build one of these, could cause stressed sleep. 😀 )
6EW6 is another pin compatible input tube with high gm, and quite linear. Worth a tube roll.
That's excellent, everyone should own at least one low cost TV Sweep tube amp. Something of a "standard candle" if you will. ( Well, owners of multiple extremely expensive "audiophile" amplifiers probably should not build one of these, could cause stressed sleep. 😀 )
6EW6 is another pin compatible input tube with high gm, and quite linear. Worth a tube roll.
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