Has anyone tried building an amp, say, with 813's, 572B's, 829B's, 845's? I've used the 807 before and it worked great- but not much different than a 6L6. My next in line will probably be the 813 then the 829b. I'll do the triodes last. There's a score of cheap sweep tubes that would be fun to try as well.:scratch2:

Yes.

Hi Guys, Happy new year 2008. I am finishing to build 811A in class A2, it will be my first experience with transmission triodes.

see, e.g., www.the-planet.org and more specifically http://www.the-planet.org/nnetg.html for some moderately exotic SE amps.

also, check the Tube DIY forum at www.audioasylum.com

see, e.g., www.the-planet.org and more specifically http://www.the-planet.org/nnetg.html for some moderately exotic SE amps.

also, check the Tube DIY forum at www.audioasylum.com
Thanks for the info. Here's one that looks good too: http://www.chambonino.com/construct/const9.html

That thing is awsome!

Hi Guys, Happy new year 2008. I am finishing to build 811A in class A2, it will be my first experience with transmission triodes.
I always thought transmission tubes would make excellent audio amps. If you go with the 572B instead, the graphite plate wouldn't hurt anything. The Yaesu FL-2100 HF amplifier uses 572's and they work superbly. Imagine what could be done with a 3-500ZG or some of the 4CX series tetrodes.

I've got a stash of 832As and a couple of circuits i've tracked down for small PP amps. Piecing together the parts for a Class A PP 6C33 amp (or if I decide to up the ante a little, maybe a PP 13E1 rather than 6C33). Got some plans to use an 807 variant without a top cap in some organ amps.

I've been keeping tabs on a couple of people, mostly on DIYAudio.com, who have been building screen-drive amps, using sweep/transmitting tubes. Amazing output from minimal tubes, and requiring ALMOST NO BIAS to get ASTOUNDINGLY good distortion spectra.

One day, I might get around to trying it... something maybe borrowing from Berning designs, or something like that... I got loads of 6JB6s and such.

Of course, the ULTIMATE SET amp would use 862s or 898s. How about 20KW audio output from a SINGLE TUBE?! :D

Regards,
Gordon.

Think of the strings of speakers you could drive :yes:, and the electrical junction box you would need :no: as you brought your entire neighborhood to its sonic knees.

I've been keeping tabs on a couple of people, mostly on DIYAudio.com, who have been building screen-drive amps, using sweep/transmitting tubes. Amazing output from minimal tubes, and requiring ALMOST NO BIAS to get ASTOUNDINGLY good distortion spectra.

One day, I might get around to trying it... something maybe borrowing from Berning designs, or something like that... I got loads of 6JB6s and such.

Of course, the ULTIMATE SET amp would use 862s or 898s. How about 20KW audio output from a SINGLE TUBE?! :D

Regards,
Gordon.

Problem is with those tubes is the mass amount of X-rays they put out. Nothing like causing radiation poisoning while listening to your favorite vinyl.

Dave

Gamma rays...jaymanaa rays...

It's the only true way to listen to vinyl!

A somewhat suspect customer of mine claims to be using pairs of Eimac 450-TL transmitting tubes as push-pull outputs. Those things are one foot tall!

--Bob

Also many of these exotic tubes use radioactive metal/gas in them - be very very careful.

Dave

Problem is with those tubes is the mass amount of gamma radiation they put out..

Umm, no, no gamma radiation. Are you thinking of the thorium used in the filaments of some of these tubes, Dave? Thorium is slightly radioactive, but it's an alpha-emitter.
http://en.wikipedia.org/wiki/Thorium

Some of the HV tubes produce considerable X-radiation (the old 6BK4 comes to mind); these were later upgraded to use leaded glass to shield it.

.

Umm, no, no gamma radiation. Are you thinking of the thorium used in the filaments of some of these tubes, Dave? Thorium is slightly radioactive, but it's an alpha-emitter.
http://en.wikipedia.org/wiki/Thorium

Some of the HV tubes produce considerable X-radiation (the old 6BK4 comes to mind); these were later upgraded to use leaded glass to shield it.

I fixed my post Mark.

Dave

I got interrupted by work between the time I started typing and I finished :-)

Problem is with those tubes is the mass amount of X-rays they put out. Nothing like causing radiation poisoning while listening to your favorite vinyl.

Dave

Hey, as long as you stay under 12000V B+, you should be fine. At least that's what the tube manuals told you, back when the tube was made. :D

It is interesting to read stuff like "If B+ voltages of over 16000 volts are used, suitable X-ray shielded must be incorporated", though, with regards to many mercury-bulb rectifiers in the same tube manual I have, that lists the 862 and 898...

Regards,
Gordon.

I've been keeping tabs on a couple of people, mostly on DIYAudio.com, who have been building screen-drive amps, using sweep/transmitting tubes. Amazing output from minimal tubes, and requiring ALMOST NO BIAS to get ASTOUNDINGLY good distortion spectra.

One day, I might get around to trying it... something maybe borrowing from Berning designs, or something like that... I got loads of 6JB6s and such.

Of course, the ULTIMATE SET amp would use 862s or 898s. How about 20KW audio output from a SINGLE TUBE?! :D

Regards,
Gordon.
Are you referring to a grounded-grid approach?

I've been puttering around with some 100THs, but haven't done anything serious yet. I don't imagine 6BH6s or 6GK6s are very exotic, but they sure bring out the best in Heathkit OPTs. Maybe I could get the Missus to pose nekked with it..............then they would be exotic...........or is that erotic.:scratch2: Eh, she ain't no fun anyhow, so I ain't even gonna ask.:no:

I've been puttering around with some 100THs, but haven't done anything serious yet. I don't imagine 6BH6s or 6GK6s are very exotic, but they sure bring out the best in Heathkit OPTs. Maybe I could get the Missus to pose nekked with it..............then they would be exotic...........or is that erotic.:scratch2: Eh, she ain't no fun anyhow, so I ain't even gonna ask.:no:
The spec's on the 100TH are very nice. That would be fun to try...

Are you referring to a grounded-grid approach?

Screen drive? Grid and suppressor grounded (actually, connected to the cathode, which is partially-cathode-biased through a moderate value resistor), and drive through the screen from a cathode follower, done either by a tube (6SN7GTB or something similar) or a MOSFET (as many of the guys on DIYAudio.com are doing).

Takes some significant B+ on the driver tube (the Berning specifies +430V on the plate and -200 feeding the cathode resistor, for a total of 630V!), but WOW... TONS of output, with almost NO DC in the transformer at idle!

This approach appeals to me because it's EFFICIENT (almost NO power dissipated in the tubes, compared to most ANY other topology), it's pretty simple (other than the aforementioned BIG TIME B+ requirements for the driver- but that's low current B+, compared to the outputs), and it seems to be just about as linear as pure class A, in comparing the output waveforms, at least from what I've read about it!

Regards,
Gordon.

I;ve been collecting tubes to eventually make a copy of Bernings amp, too. The way Jack raved about it made me interested in the design.

Of course, the ULTIMATE SET amp would use 862s or 898s. How about 20KW audio output from a SINGLE TUBE?! :D

Regards,
Gordon.

898's have 210 amp filaments. At 33 volts. What wire do you use to carry that much current? Not to mention, the HV is 13 amps at 12 kv. You need 16 gauge wire or maybe even bigger for 13 amps!
... I want one.

I once purchased a pair of 851 tubes. Look those up in your TT-5! VERY COOL LOOKING. I sold them to a guy in NYC -- after luckily finding someone willing to carry them to NY in the backseat of his car -- who was planning to build amps around them. I wish I had some good pictures of those tubes now. Filament wanted something like 11.5v at 13.5A. What I liked was that they looked like a regular tube in shape and structure and glass envelope, but just WAY BIG.

You know what they say about someone who wants BIG tubes... :)

Im in the process of building an 813SE amp. Nothing crazy; or even out of the ordinary so much....I can say that anything with a B+ of 700v or higher does take quite a bit more thought in the PSU area. Also, not like there are 1000's of circuits out for these tubes; so you either build what is out there; or try all kinds of different approaches until you find one that ya like.

I;ve been collecting tubes to eventually make a copy of Bernings amp, too. The way Jack raved about it made me interested in the design.

I actually have four 6JN6 tubes, IIRC... need to look at my lists again. :scratch2:

The high-voltage rated 6SN7GTBs (I don't think the 6SN7GT or GTA can handle the voltage?) might be another hurdle...

Regards,
Gordon.

Im in the process of building an 813SE amp. Nothing crazy; or even out of the ordinary so much....I can say that anything with a B+ of 700v or higher does take quite a bit more thought in the PSU area. Also, not like there are 1000's of circuits out for these tubes; so you either build what is out there; or try all kinds of different approaches until you find one that ya like.

I got a friend who is also trying that, but doing it very slowly as he is in the process of moving. I've always wanted to do a forced air cooled amp with the eimac 4CXxxx transmitter types b/c they are so cheap, but i can't think of a situation where i would need so much power, unless it were to be SE as well, but then again i have too many projects as it is.... anybody build an amp with those?

I got a friend who is also trying that, but doing it very slowly as he is in the process of moving. I've always wanted to do a forced air cooled amp with the eimac 4CXxxx transmitter types b/c they are so cheap, but i can't think of a situation where i would need so much power, unless it were to be SE as well, but then again i have too many projects as it is.... anybody build an amp with those?


I've got a small stash of those, but haven't done anything for the same reasons you mention. I really want to do a SET with TH 100s though. I have lots of the parts collected including a 50 pound 5000vct TX. I joined the GM70 yahoo group but those guys talk so far over my head it ain't even funny. That kind of amp building appears to be a whole different ballgame. I even bought a HV probe for my Fluke 87.:D I imagine the exspensive part would be having the OPTs wound. Probably need interstage TXs too.:drool:

Also many of these exotic tubes (have) radioactive gas in them...

Me too... :sigh:

I've got a small stash of those, but haven't done anything for the same reasons you mention. I really want to do a SET with TH 100s though.

I thought the cool way was 100-TL rather than TH, with TL being the low-mu version (that is very hard to find). L = low, H = high.

I imagine the exspensive part would be having the OPTs wound. Probably need interstage TXs too.:drool:

Yup! But there's always vintage stuff (http://cgi.ebay.com/UTC-LS-845-Output-and-LS-6-Driver-Transformer-845-Tubes_W0QQitemZ330195985583QQihZ014QQcategoryZ6781 5QQssPageNameZWDVWQQrdZ1QQcmdZViewItem), eh?

UTC LS-845 iron:
http://tubino.smugmug.com/photos/240051608-L-0.jpg

But that's PP, of course...

Maybe an 845 isn't exotic anymore, but it can still get ya some watts. All images swiped from ebay auction linked in previous post.

http://tubino.smugmug.com/photos/240053733-L.jpg

http://tubino.smugmug.com/photos/240053688-L.jpg

http://tubino.smugmug.com/photos/240051608-L-0.jpg


Im in love:drool:

Im in love:drool:

Me too. Was it the specs, or the good looks that gotcha? Here's the cheesecake shot for me:

http://tubino.smugmug.com/photos/240322805-L-0.jpg

hey-Hey!!!,
I'd love to get one of those for the ongoing Unwinding Project. Unfortunately, that is *NOT* a scrappless core stamping so making that iron w/o cut C cores is going to be unlikely. Getting initial perm to match the interleaved EI is perhaps best done with a 49% Ni core...so this puppy could be quite stellar.

Currently I am getting a fair service from the Heyboer wound Peerless S265's. What I need is a project to use the S271S on...or perhaps the new Thordarson T-3S16. That one has cast endbells too, what a pretty piece.
cheers,
Douglas

What I need is a project to use the S271S on...or perhaps the new Thordarson T-3S16.

Specs?

Think those guys can wind some good SE xformers? For value and sound quality, they'd have to go some to beat the James 20w units that Euphonia sells for $215/pr. Max pri. imp. on those is 5K (multitapped), but if they could do a 20w unit with 8K or 10K, what a wonderful thing it could be.

OTOH, I think Paul de Clerc opined that 5K would be about right for a triode-strapped 813 the way Pete Millett was doing it...

Specs?

Think those guys can wind some good SE xformers? For value and sound quality, they'd have to go some to beat the James 20w units that Euphonia sells for $215/pr. Max pri. imp. on those is 5K (multitapped), but if they could do a 20w unit with 8K or 10K, what a wonderful thing it could be.

OTOH, I think Paul de Clerc opined that 5K would be about right for a triode-strapped 813 the way Pete Millett was doing it...

Tubino!...:)

The S271S is the 20-20 Plus series, 5k a-a, 80 Watts. You'll have to do without a few plates of Ni in the stack, trivial really unless you're getting told it is complete and authentic as originally built.

Given that 813 triode plate Z is between 2 and 3k for most of the useful swing, I'd suggest 6-7k load SE. That's for getting a reasonable damping factor if the amp is otherwise open-loop.

I think I'll try them 10k a-a with 40% U-L tap for the g2 and run some E-Linear FB. In truth, I think that config wants more like 6k a-a but that's at B+ less than 600V.
cheers,
Douglas