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I’ve never made a Spud amp. This thread is to chronicle my adventures making a single-ended Spud amp. That’s just one tube(er). And perhaps the purist approach is a tube with only one vacuum device inside. So the 6BM8 is out of the running.
What started me off was a friend offering me a Hammond 125ESE output transformer in return for a nice burger. This OPT has a lot of flexibility. And so I’ve bolted it down onto my universal test rig.
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6E5P: the basis for the first version of this amplifier is a neat little Tetrode. It's a lively tube that punches above it's weight, however the smoothest sound comes from Triode operation.
6p15p: this is a true Pentode and the approach being considered is in schematic in post 22 and discussion starting post 65
What started me off was a friend offering me a Hammond 125ESE output transformer in return for a nice burger. This OPT has a lot of flexibility. And so I’ve bolted it down onto my universal test rig.
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6E5P: the basis for the first version of this amplifier is a neat little Tetrode. It's a lively tube that punches above it's weight, however the smoothest sound comes from Triode operation.
6p15p: this is a true Pentode and the approach being considered is in schematic in post 22 and discussion starting post 65
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That must have been a really, really good burger. When I first started getting interested in tubes, the 125ESE was about 35 bucks a pop. Now it's over 50, (considerably) and rising. These days I look to folks like Edcor, Transcendar, and (maybe) Musical Power for budget transformers.
Having said that, my second tube amp (first designed, second built) was a single-ended affair using pentodes, mosfets, screen-driven sweep tubes, and the 125ESE. It was a sweet sounding amp for something built essentially out of junk.
Having said that, my second tube amp (first designed, second built) was a single-ended affair using pentodes, mosfets, screen-driven sweep tubes, and the 125ESE. It was a sweet sounding amp for something built essentially out of junk.
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Thing about using a triode-pentode combo in single tube is that it looks like a spud amp but to my twisted thinking it's no different than a two-tube SET amp. I'm excited about the challenge of using just one device.
I hadn't realized how expensive these OPTs have become, mind you the burger that's owed is from a local place known to have exceptional good burgers
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Ah yes the 6SPUD5 tube. An old Russian standard. Good for a long winter project. One can make many things from that. I find that it makes for a good horizontal deflection device.
Where is the getter located?
Have you considered a flywheel for energy storage?
Who needs money when you can work for OPT's
Where is the getter located?
Have you considered a flywheel for energy storage?
Who needs money when you can work for OPT's
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I really like the classic curves of the 6SPUD5 too (pentode, triode):
"Where is the getter located?"
We just wrap them on top with aluminum foil. But one could just puncture them with a fork to let the steam out.
"Who needs money when you can work for OPT's"
We have "tubecoin" now.
How about a special exemption for SPUD amps, you can use as many (useless) 6LE8, 9KC6, 6BN6, 6ME8 or 6JH8 as you want, as long as those are the only "tubes" used. Sort of like a "tubeless" tire, we could call it a SPUDless Amp.
"Where is the getter located?"
We just wrap them on top with aluminum foil. But one could just puncture them with a fork to let the steam out.
"Who needs money when you can work for OPT's"
We have "tubecoin" now.
How about a special exemption for SPUD amps, you can use as many (useless) 6LE8, 9KC6, 6BN6, 6ME8 or 6JH8 as you want, as long as those are the only "tubes" used. Sort of like a "tubeless" tire, we could call it a SPUDless Amp.
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So many nice tubes so little time. Well, rules say one device so how about 6P15P, 6CL6, EL84 ?
Triodes have too low gain-power so Pentodes is where it is at. Some decent levels of transconductance are desired here, no 6V6 type tubes or tomatoes!
Can't a Pentode sound good - I thought somebody over at Hawthorne Audio (?) had a spud kit based on a simple cicuit which was well regarded.
Triodes have too low gain-power so Pentodes is where it is at. Some decent levels of transconductance are desired here, no 6V6 type tubes or tomatoes!
Can't a Pentode sound good - I thought somebody over at Hawthorne Audio (?) had a spud kit based on a simple cicuit which was well regarded.
They were offering a 6CL6 amp several years ago when I bought my speakers.
The pulse regulator beam triodes are a possibility. Frame grid. Mu of 300, Gm about 60,000 depending on which tube. Plate dissipation 25 to 35 watts. Positive grid voltage REQUIRED for reasonable plate voltages. The 6HV5 is the most common flavor...
....warning these things just love to oscillate, especially when connected directly to a high Gm mosfet. I have a LARGE pile of toasted silicon on my bench at this moment along with at least one dead tube. A shorted fet put +300 volts on the grid and it was literally gone in a flash!
Single stage amp? I am assuming that some sand based life forms will be allowed in support roles? If you have one active tube stage per channel, that implies silicon rectifiers, how about a mosfet to drive the grid(s)?
Drive requirements? Does it need to be fed from a CD player, or the headphone jack of an iPod or cellphone?
Assuming that's OK, I might have something on the drawing board if I can keep it from blowing up. There really are the TFH!
OK, but seriously now....
I figure that if I can collect up all these useless old TV tubes and throw them at the spokes of my flywheel, then I can find a use for them. The only deal is that they would break when they hit the spokes. I guess that could be called a "one shot".
...ah yes the foil getter & de-gas (sounds like a futuristic 50's rock a billy band) "But one could just puncture them with a fork to let the steam out" Steam yes, smoke no.
don't forget about the 6AN8, Pd of two watts []<~
I'm all about special exemptions, I believe there could be some Federal Dollars available for this project. The P.A.A. (Potato Growers Association) "A Professional Society for Advancement of the Potato Industry" may just be interested, who knows.
Nice traces, these I will include in my proposal to the P.A.A.
I figure that if I can collect up all these useless old TV tubes and throw them at the spokes of my flywheel, then I can find a use for them. The only deal is that they would break when they hit the spokes. I guess that could be called a "one shot".
...ah yes the foil getter & de-gas (sounds like a futuristic 50's rock a billy band) "But one could just puncture them with a fork to let the steam out" Steam yes, smoke no.
don't forget about the 6AN8, Pd of two watts []<~
I'm all about special exemptions, I believe there could be some Federal Dollars available for this project. The P.A.A. (Potato Growers Association) "A Professional Society for Advancement of the Potato Industry" may just be interested, who knows.
Nice traces, these I will include in my proposal to the P.A.A.
I think you are onto something there. Those people in South Dakota who build the Corn Palace might be interested in commissioning a Corny Amp.
We could just drill out the corn cobs, and slide them over the slim 7 and 9 pin tubes. Cook the corn on the cob, while listening to amplified Hee-Haw music. Hot cored spuds too.
We could just drill out the corn cobs, and slide them over the slim 7 and 9 pin tubes. Cook the corn on the cob, while listening to amplified Hee-Haw music. Hot cored spuds too.
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The Potato Cops are on their way...
It would be so much fun if there were prepared kits available and distributed to willing contestants. Full of well thought out "alternative" components that could & would work well enough to allow the project to be judged against some sort of criteria. Spl, bandwidth, THD. But the methods would have to be secretly researched and then used to build the parts kit. Which would include really silly stuff like a lamp dimmer, perhaps an old floppy disk drive, the tube & socket. Everything in the "kit" would be the same. Then will meet up at some convention/hamfest somewhere to be judged with a winner.
It would be so much fun if there were prepared kits available and distributed to willing contestants. Full of well thought out "alternative" components that could & would work well enough to allow the project to be judged against some sort of criteria. Spl, bandwidth, THD. But the methods would have to be secretly researched and then used to build the parts kit. Which would include really silly stuff like a lamp dimmer, perhaps an old floppy disk drive, the tube & socket. Everything in the "kit" would be the same. Then will meet up at some convention/hamfest somewhere to be judged with a winner.
Well there was a guitar Amp contest/thread for $200 max parts cost, or something such. George/Tubelab would have the particulars.
Some other themes in the past have been the most in-efficient Amp. But that was too easy.
Using the most tubes would be interesting, but the tube sockets cost way more than the cheapest TV tubes.
Getting 20 frame grid tubes to work in parallel, without oscillating, might be an interesting theme. This could form a single stage Amp.
Or how about getting 100 Watts from a 12AX7 for so many uSecs. (Ehh, we already know George would win that one)
"Potato Growers Association"
Wouldn't that be the PGA? I always wondered what they hit around before the invention of the golf ball.
Some other themes in the past have been the most in-efficient Amp. But that was too easy.
Using the most tubes would be interesting, but the tube sockets cost way more than the cheapest TV tubes.
Getting 20 frame grid tubes to work in parallel, without oscillating, might be an interesting theme. This could form a single stage Amp.
Or how about getting 100 Watts from a 12AX7 for so many uSecs. (Ehh, we already know George would win that one)
"Potato Growers Association"
Wouldn't that be the PGA? I always wondered what they hit around before the invention of the golf ball.
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I started down the road to an amp using 16 X 13GB5/XL500 (8 per channel)since I have a bunch of them. The sobering moment came early, during the heater wiring. That's when I thought "what the F*&% were you thinking". Sanity reeled me back in and that thing hit the trash, after ripping out the tube sockets.
It was a $100 total parts cost "TUBE guitar amp" contest. It is a sticky at the top of the "Instruments and Amps" forum. It was started because someone with an amp kit to sell stated that nobody could design a better amp for less money, to which I replied "wanna bet?"
A third party proposed the contest, but didn't fully explain the rules, or what constituted a "TUBE AMP." I asked the same question about mosfet followers early on in the thread, and they were allowed, but remained a sticking point throughout the entire contest. Just what parts get counted in the $100 total also caused some grief.
Yes, I can build a simple 4 tube guitar amp for under $50 in parts, not counting the chassis (I didn't use one) or wood cabinet (I made it from scrap wood). The 5 tube, 20 watt screamer costs less than $100. Both will be revisited once I finish my new lab.
Overall the contest had it's desired effect. Several cool designs were proposed, and built. The schematic and design details are still there for all to see and use.
"The sobering moment came early, during the heater wiring. That's when I thought "what the F*&% were you thinking"."
Yeah, I hear you there. Paralleling a bunch of TFH is looking real flaky now too. Matching, sockets, parasitic oscillation, individual bias adjustments....
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"Which would include really silly stuff like a lamp dimmer, perhaps an old floppy disk drive, the tube & socket. Everything in the "kit" would be the same. "
One thing for sure, it can NOT include a clock or batteries or electrolytics. We would all be arrested if they took their finished contraption to school.
Yeah, I hear you there. Paralleling a bunch of TFH is looking real flaky now too. Matching, sockets, parasitic oscillation, individual bias adjustments....
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"Which would include really silly stuff like a lamp dimmer, perhaps an old floppy disk drive, the tube & socket. Everything in the "kit" would be the same. "
One thing for sure, it can NOT include a clock or batteries or electrolytics. We would all be arrested if they took their finished contraption to school.
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