The AM Forum

This is the way to do it!!   :D

http://gizmodo.com/gadgets/home-entertainment/roth-mc4-music-cocoon-ipod-dock-is-a-series-of-real-tubes-241538.php (http://gizmodo.com/gadgets/home-entertainment/roth-mc4-music-cocoon-ipod-dock-is-a-series-of-real-tubes-241538.php)

Brian - W8KHZ

Yup, must be high end audio, if they're using tubes.  I see that the 12AX7 tubes are Sovteks (Electroharmonix branded - Mike Mathews of Electroharmonix,has been involved with Sovtek,since the early 90s, when he convinced them to make 5881s and 12AX7s for guitar amps [at the time, the supply of tubes for guitar amps, and Electroharmonix sells equipment in the electric guitar market]). 

73,
Ellen - AF9J
Guitarist at large

The first two stages in my mic preamp uses 12AX7's.  Wonder if it would be worth $779.

Real hams use UX201As in their preamps; thorium filaments are a must!

12AX7s have wimpy oxide coated cathodes...

tom

Interestingly, high intensity, high repitition fire rate gaseous diffusion lasers of the type that might be used in aircraft use vacuum technology, right down to focused cathode to cathode emmision (high emmision area of the cathode and of a material very similar to velvet (carbon) of all things.)
Most kids are very interested in lasers.  Hmmm, might 8877 technology rules once again?
I understand the only things holding back deployment are not achieving 10k rounds reliably and the disintegration of the aluminum grid/plate before 10k.   Yeah, long live Mechanics Illustrated, my reliable source.

Actually I can tell you from personal experience Tom, that 12AX7s are pretty sturdy tubes.  I purposely used to run the gain on my guitar amps, and pre-amps to produce  extremely heavy distortion (which sounds cool in guitar) from the 12AX7s. Heavy distortion is always hard on tubes.  But my 12AX7s used to last through years of heavy distortion use, before I'd change them. Even then, they didn't fail.  They were still usable when they weren't driven extremely hard, and used in clean sounding applications.  It's just that they weren't sounding as good as they used to, so I'd change them.  BTW, the 7025 is supposed to be an industrial version of the 12AX7.  I wonder if maybe this version uses thoriated tungsten filaments.

73,
Ellen - AF9J

I agree Ellen that 12AX7s are sturdy, but they're also quite modern. Equipment with 12AX7s just doesn't look vintage enough.  For me, 6SN7s are about as new as I like to go.

Tonight, I'll be using my 9 tube (UX201A, of course) 1924 TRF receiver on 160 meters.  And it's not a boat-anchor; those receivers were called coffins (although the shape is more like that of a casket).  It's kind'a neat.  There are about a half-dozen ~500 pF air caps connected with a wires (for single control tuning), and there are another half dozen smaller air caps for trimming the big caps.  I'd say the wooden box is about 4 foot long.

It's a good partner for a class e transmitter.  My S-38A isn't nearly as good.

Stop messing around with the new fangled 01s and break out the galena or carborundum. Or maybe a filings coherer. ;)

We love vacuum tubes here at W2XR.

I'll take my WE 300Bs, WE 262As, WE 417As, 6SL7s, 6J5Gs, and 76s anyday.

And yes, I use 12AX7s and 12AU7s in the microphone preamp for my AM rig, along with 6J5s, 845s, and triode-connected 6J7s in the audio driver.

Keep 'em glowing, and of course, real radios and stereos glow in the dark!

73,

Bruce

Tom,

That is some seriously cool stuff.  Since you're into Vintage radio, have you ever read Dave Ingram, K4TWJ's book "Golden Classics of Yesteryear?  It has circuits of different popular designs from the 20-50s in it.  Many of which are buildable.   

73,
Ellen - AF9J