Speaking of the 807, I wonder what kind of power can be gotten out of them in SE pentode? what about a pair in parallel SE? The anode in pentode mode can take a lot of voltage thanks to the top cap. Would it give up the amazing (IMO) sound it gets in the Firebottle if it got cranked up? If Dennis ever made an amp like that I’d be sorely tempted. Being who I am I would probably request it with regular octal sockets so that I could adapt them to 807, 5b/254m, and 6gb6.

Huh, looks like Gordon Rankin already tried a higher power 807 SE amp with mixed results. https://www.fidelity-online.de/wp-co...ractices-2.pdf

The resulting power isn’t all that much more than what we can get with the KT88 Firebottle. I am also curious if the 20lb output transformers are really necessary. The extra handful of watts requires that much of a jump? I know both Gordon and Mike were both experienced designers but I dunno, seems like the OT could be smaller and less expensive.

Here we go again...
 

Time to get started on my new build, the PSE 8417. I doubt this will ever be an official Inspire offering, since Dennis doesn't like to build commercial offerings featuring hard to source tubes, and 8417's are not just lying around everywhere.

But, I have been looking at this tube for awhile. One might consider it one of the final culminations of the tube designer's art, as it was one of the last developed power pentodes developed before germanium and silicon made tubes "obsolete".
Yes there have been newer tubes developed, like the KT-90/120/150/170, but in my mind these are mere iterations of an earlier design, and not something new and different like the 8417. And since I have a reasonable stash of 8417s, I decided to see what this tube was capable of...

I decided to reuse the Slammer's power supply, albeit upgraded to provide the B+ voltage the 8417 is capable of handling.

However, first order of business was getting the corners welded up and then prepped for cutting/powder coating...

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And after a lot more sandpaper mixed with elbow grease, here's one of the welded corners ready for cutting.

https://live.staticflickr.com/65535/...285cd703_b.jpgUntitled by analog addict, on Flickr


However, once I had the chassis ready, I found out that Straitwire was just too busy to cut my chassis, so I was going to have to do it myself. Ugh...The job I like the least when building amps from scratch. So be it.

Next was getting the design laid out for cutting. Dennis gave me a push by getting the first couple of sockets laid out, and then I finished it out.


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Here's what the topside will look like once put together.

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Unfortunately, in the next five weeks, I'll be out of town for three of them, so it will be slow going for awhile.

Stay tuned.

Hmmmmm....Dennis has a BIG pile o 807's lying around the shop. Wonder if he'd consider a PSE 807?

Perhaps.

If you are really interested and he isn't, I could put one together at some point, of course with Dennis' guidance...:thumbsup:

The 807 has become one of my favorite tubes. Well, them and their “equivalents” like vt60, 6bg6, and 5b/254m. I mostly run them in push pull these days. Have been very, very impressed using c3m tubes in triode as drivers. Running the 807 in ultralinear 350v 60ma per tube.

I have gone back to the KT88 Firebottle recently. Right now I am using 6ar6 outputs with a bl63 driver. Wonderful open and warm sound with plenty of bass. You have to use an adapter with the 6ar6 but the tubes are still cheap. Remarkable considering how high a quality tube it is.

Think Globally, act now....
 

Dennis has recently gotten a bee in his bonnet to start playing around with the "old man" tubes again after someone ordered a 45 or a 2A3 amp from him. He has modified the circuit once more and has come to the conclusion that Globe 45's are the best thing since sliced bread.

Gee, I wonder who told him that 5 years ago...:D

Anyway, this is his new amp. The (globally inspired) Fire Bottle SET 45...

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I believe there will be a small production run of these until they're gone. The 45 SET with ST shaped tubes will be $2750 +S/H and the same amp with globe 45s will be $3150 + S/H and is available in either Inspire Red or High Gloss Harley Black.

PM me to order yours today!!!

I’ve always been intrigued by a 45 based amp but have never had speakers that could even use 2a3 let alone the 45. You must need an incredibly sensitive speaker to use this.

If my status as a tube hipster wasn’t obvious, I have now cemented it with my current combo in my KT88 Firebottle. I am using a Marconi b36 (via an external heater supply) and GEC cv4062 outputs.

I’ve been told that these are related to or in the same family as the el84 but with a different pin out. There was an upper midrange glare with several input tubes but this metal based b36 seems to have mostly tamed that. It is still giving me a very clear sound. I’m not used to sound like this from a single ended amp. It has a precise, clear sound. Still a bit of a metallic sound on some recordings though. I will try the n78 soon, another GEC tube with the same specs.

These particular tubes are another case of the adapters costing more than the tubes. Not sure it’s going to work out for this amp. There are plenty of other tubes I prefer over these and with much less exotic drivers. I’m hoping they will sound better in my push pull amp.

6actually no. Dennis is able to drive all these speakers with his new 45...

https://live.staticflickr.com/65535/...a37c8256_b.jpgUntitled by analog addict, on Flickr

As long at the speaker's efficiency is 90db/w/m, this amp will drive them fine...

Meanwhile Dennis is hoarding all the globe 45s he can find. Toobs are better than money, cause they'll print more money....

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3 of those look like they would be pretty high sensitivity. My speakers are around 90db sensitive and I have gone as low as 4w with decent results. I do think one of the reasons my push pull amp can sound better (depending on tubes) is just having more power.

One of the best systems I have ever heard used a push pull 300b amp. It was a custom amp made by Deja Vu Audio in the DC area and hooked to a pair of Quad ESL63 speakers. Would love to hear some other triodes like the 2a3 or 45 like that.

I have run triode wired 12av5 in my push pull amp. The *av5 tubes have the reputation of being very similar to a 2a3 in triode. Sylvania even sold some wired internally as triodes to the government as 6b4ga which is supposed to be a directly heated tube very similar to a 2a3. They were probably being used in power supplies in measurement equipment or something. Anyway, they sounded really good in my amp both in triode but especially in ultra linear. It would be cool to see what magic Dennis could wrangle out of them both in all the output modes. I'd probably trade my KT88 firebottle towards that if he got something he thought was great.