I've been messing with them for about 20 years, and there's nothing more I enjoy talking about. I'm not interested in discussing what's best for under $300. I'm more about discussing the merits of different output tubes, transformer suppliers, parts and design. If I ever manage to learn how to post pictures, I'd like to share designs I'm working on and maybe provide schematics.

For posting pictures you just need a share site, The picture needs to be on a web site, that can be your own. Lots of free options. I have stuff on my own web page like the this picture here. Also I started using an extra  page I made on facebook as it was faster than updating my web page.
 Make your self a ampfixer facebook page, you can make extra sub accounts using you existing account.  Then post your pictures there, then all you need to do is right click the photo and   "copy image URL"  paste that into the dialog box in the forums picture tool. 
 
This is my amp for last 25 years, 1972 Princeton, no reverb. I had it rebuilt by someone like you. He changed the tremolo into another gain stage, so added a Pre and Master volume as well as Midrange. I put a Celestion Vintage 30 in it too. My son is an electrician and started learning about fixing tube amps as a hobby. So he re tubed it last year as it was dying on me. 

I'm interested, but I'm afraid it might be a one way discussion as I doubt I can offer you much knowledge. 
 
But I'd be quite curious to know how and why you might choose to differ from the classic sorts of standard designs from the 50's and 60's to achieve what you are after.

In recent discussions with a friend of mine (who's pretty knowledgeable about amps and such) regarding my apparent lack of valves (specifically, the vox amphones being solid state), for a joke I 'shopped a pair of engine valves onto the bins.
 
...and this got me to thinking along these lines:
 
"I'm considering the possibility of designing an audio amplifier using engine valves as the amp engine.

You need to convert a little something into a big something, so if you had a high pressure air source behind the valve, and the valve was operated by a fast actuator driven by the audio signal, then the valve would open and close at the audio frequency rate and the amount it opened by would be dependent on the amplitude of the audio.

Maybe a set of different sized valves would be the way to go, driven via a multi-band frequency divider."
 
So I did a bit of investigation, and lo: 

http://en.wikipedia.org/wiki/Compressed_air_gramophone
 
http://www.aqpl43.dsl.pipex.com/MUSEUM/COMMS/auxetophone/auxetoph.htm
 
http://windworld.com/tools-techniques-ideas/acoustic-amplifiers/
 
The auxetophone link contains a link to a you tube video where somebody has a working model.  I think you can tell from the video how ridiculously loud this thing was!  ("It was capable of producing sufficient volume to broadcast public music performances from the top of the Blackpool Tower, and was said to be loud enough to cause people to vacate the front rows of seats in an auditorium.")  Using an internet interest calculator thing I worked out that at the time it would have set you back over £13,000 (in today's money).
 
Anyway, hope you find this of interest :-)

And that's why we (Brits) call those hot glass things Valves (not tubes) because they act the same way as a mechanical valve.
 
I'm certainly interested in chatting about amps.  I have an old solid state Marshall 2x12 combo that sounds awful, a 1963 Vox AC15b that I restored from the chassis up which sounds awesome.
 
But my favourite atm is the Trace Elliot AH1200-12 pictured in my avatar.  A bass amp?  Yes, and with its 4x10 cab and a 1x15 cab and 1.2Kw output it sounds INCREDIBLE.
But the best part....  it has a 12ax7 stage in parallel in the input stage with a drive and blend control.  I'm not a great fan of distortion/overdrive on bass but the valve does warm/smooth out the tone when used in moderation.
 
However...  plug a LesPaul into it and crank up the tube drive and INSTANT ANGUS YOUNG!!!!1!!  (that's called thinking outside the box )
 

 
I love amp discussions and will follow this thread, for sure.  I always learn something from following these types of threads, lead by experienced folks.  Here is what I am currently playing.  Strat, LP, 335, all sound awesome through real valves.
 
 

Does any clever person here know what the limiting factor in valve size is?  They're still pretty chunky even these days, so I was wondering why miniaturised valves running on lower voltages haven't been produced yet.  Perhaps there's a scientific reason?
 
@ ampfixer, to post a picture, host it on a site like photobucket, flickr etc. then use the 'Insert/edit image' icon and enter the URL to the image.
 
e.g. 'Valved amphones'
 
 
 
 (That's not me btw!)

ston
Does any clever person here know what the limiting factor in valve size is?  They're still pretty chunky even these days, so I was wondering why miniaturised valves running on lower voltages haven't been produced yet.  Perhaps there's a scientific reason?
 
 
 
 

Russians have big fingers. More suited for stuffing sausage. (it sounds like a good idea though. I've chased tone down way goofier rabbit holes than that.) 

This is encouraging. I don't think I can help Ston make an amp from engine parts. All the valves I know about are glass. As for why there's nothing new being developed, well, making tubes is a dirty, nasty business. All of the production is in eastern Europe, Russia and China. Back in the day, they used to be made in America, England, Holland and Germany. 
 
There are a lot of toxic substances that go into the coatings used to treat the cathodes and plates. Things like arsenic, cadmium, lead (sometimes in the glass) and other heavy metals. Most of the assembly is done by hand. In order to be profitable with tubes (valves) you need a lot of cheap labour and lenient environmental regulators. (In my opinion)
 
There are still some industrial applications that require tubes but it's mostly hi-fi and guitar amps now. Low voltage designs are beyond me. If there's interest I could post something on how tubes actually work. At the heart of it, the principle is one of differences. You have to have a high potential at one end and low potential at the other. This pulls electrons from the low side to the high side. A third potential is applied between the high and low to regulate the flow rate. This is where the term valve comes from. Trying to do it with low voltage would be tough.
 
I pick valves for my design based on availability, so I only use valves that I know folks will be able to buy into the foreseeable future. There are hundreds of different types on the market but most are no longer in production. This is an important point if you come across old amps. You have to avoid out of production tubes unless you know enough to rewire the sockets.
 
I know how you are supposed to post links but so far no luck. There's some sort of security thing going on with the drop box that I have to sort. Right now I'm building a newer design I call the Producer 88. It's a 15 watt amp running a single KT88 for the output. It has a simple 3 band EQ and is designed for the needs of a small studio. It will be documented in a series that I'm doing for thetubestore.com and posted online in 2 or 3 articles. I've helped them with reviews and articles for a number of years. You may find some interesting stuff on their web site.
 
If you have any amp related questions post them in this thread and I'll try to answer them. Remember, I know NOTHING about solid state. It's voodoo and I avoid it.

sure lets go Brit …..the guts of one of my amps ….only  200 made it to the US  I've been told .
 
 
 
 

 

 
 
 
 
you want some Fender ?
 
 

 

 

 

 
just a little taste to get the ball rolling  
 
Kenny