interesting valve...

[DummyLoad]

4D22/32 choose your filamentary poison.... 

http://scottbecker.net/tube/sheets/138/4/4D22.pdf

yes, it has a plate cap. 

two tubes make >100W w/o insane power supply V.
decent sensitivity - 74Vp-p drive to make 100W.
they are ugly as $#it.
the sockets are probably expensive and rare.
tube itself seems like they are still plentiful (or so it seems) & they don't cost a small fortune (yet?).
the OT is not an insanely high input Z (3KΩ) as required by other similar xmitter tubes that run at higher voltages to make >100WRMS.
power supply seems doable with a FW doubler and 600Va & 300Vg2.
probably far more reliable than russian/sino 6550/KT88 variants currently on the market.
4 tubes run in AB1 into 1K5Ω load should make ~225W - perhaps hammond 1650W; 280W, 1K9Ω Z pri w/ some g1 tweaking would work - need to plot some load lines but at first glance seems like it's workable.
there's always the spares issue, and weight, and the plate caps....
what ever happened to the all the ampegs that were 6146 equipped?
just passing the time...

thoughts?

--ISO_el_insane-o

[FYL]

the sockets are probably expensive and rare.

Septar sockets cost between $10 and $15 ea at Surplus Sales.

http://www.surplussales.com/tube-sockets/TubeSkts-4.html

tube itself seems like they are still plentiful (or so it seems) & they don't cost a small fortune (yet?).

Plentiful? I'm not sure. Obscure ref, single source, $85 to $95 ea. depending on seller.

probably far more reliable than russian/sino 6550/KT88 variants currently on the market.

Better built, but designed for fixed broadcast applications, presumably with some added cooling. Dunno how well they'll perform in a geetar amp. AB audio looks like an afterthought, stability could be a big problem.

what ever happened to the all the ampegs that were 6146 equipped?

Some got converted to 6550Cs...

[DummyLoad]

much thanks for the link to the sockets. 

Plentiful? I'm not sure. Obscure ref, single source, $85 to $95 ea. depending on seller.

http://cgi.ebay.com/RAYTHEON-JAN-4D32-TUBE-/400166254011?pt=LH_DefaultDomain_0&hash=item5d2bc475bb

http://cgi.ebay.com/RAYTHEON-4D32-POWER-AMPLIFIER-TUBE-AUDIO-RF-AMATEUR-HAM-/150535403998?pt=Vintage_Electronics_R2&hash=item230c9bf9de

two seller have them for 25 clams ea. + ship.  more single by sellers - price range varies from 40 and up.

SS of Nev. has them @ 35 ea. less if buy 3+.

--ISO

[FYL]

two seller have them for 25 clams ea. + ship.

Much better...

SS of Nev. has them @ 35 ea. less if buy 3+.

They add "Very Hard to Find Transmitting Tube"...

So if you plan any kind of build using them, get a lifetime supply.
 

[DummyLoad]

So if you plan any kind of build using them, get a lifetime supply.
 

ayup...   

[Geezer]

WOW! Some of the sockets @ Surplus Sales are over $1800.00 each! 

[DummyLoad]

yup - made of pure silver. best conductor. 

somehow, i don't think it'll smelt down to $1800 worth... 

[FYL]

WOW! Some of the sockets @ Surplus Sales are over $1800.00 each!  

Quite complex - and beautifully made - HF assemblies for ceramic broadcast tubes. The model above is dedicated to the Siemens RS1084CJ, a water-cooled beast able to put out 75 kw (75,000 watts) at 10 MHz!

 

[HotBluePlates]

two tubes make >100W w/o insane power supply V.
decent sensitivity - 74Vp-p drive to make 100W.

...

thoughts?

Be sure to read ALL of the data sheet.

I saw a note under AF service that the grid leak (i.e., grid reference) resistors must not exceed 25k per tube. You generally want a stage ahead of the output tube with an output impedance 1/4 (or less) of the input impedance of the output tubes (~60k output-Z into 220k input-Z for a common 12AX7 PI to output stage).

So a phase inverter (or PI-into-driver) circuit with an output-Z of around 6k (or less) is gonna be needed. Do you have such a special driver stage ready for it? A phase inverter into a cathode follower driver is possible, but you'll need more output swing from the PI to make up for the follower's losses, and the h-k voltage rating of the tube may present a problem. You might need an elevated heater voltage just for the driver stage.

[PRR]

Just get one.

400Vp
300Vg2
-30Vg1
150mA
2.5K load
25W out

Yeah, that's 60W plate dissipation. The ratings are CCS, Continuous Commercial Service. 24/7 with no breaks and high cost (or lost income) from downtime. As a hobbyist gitar amp you can go 20% higher.

http://www.radiomuseum.org/images/tubephoto_klein/usa_4d22_001.jpg

[DummyLoad]

was considering driving w/ 6SN7 -or- 6BL7 configured as a CF - perhaps a williamson type, ampeg SVT or genalex ckt. elevated heaters are likely - at least for the driver stage. actually, i haven't even touched on that part of the design yet  - i'm still sorting out the iron issues. thank you for the forewarning and it is appreciated.

PRR, interesting SE turn. so what you are saying, more or less, is that ICAS ratings are acceptable for geetar use?
same issues in SE tho - low R for g1 ckt.. perhaps a 12AT7 driver?

doodling... for driver.
12AT7 - 2 triodes in || config.

B+ 300V
Ra 33K
Rk 330R
Ck 100uF
Vbias ~~ -1.5V
Ibias~~ 4.8mA
Vo ~~130Vp-p
Zout ~~4.8K 
AV ~~38
above calculated into an Rload = 22K (g1 ckt of 4D22)
Cc = 100nF for F-3dB ~~60Hz. -or- perhaps use 150nF? for 40Hz F-3dB?

maybe a twist and drive it with a single compactron - like a superchamp? only use 5u4gb for recto.
6K11 is 2 x 12AX and 1 x 12AU - i have a 2 or 3 on hand.
2 x 12AX - the usual fender Ra=100k, Rk=1K5, Rload=1M, etc.. the 12AU driver tho...

does seem to like a similar config as the || 12AT above, only w/ a singe triode achieves nearly the same performance with the exception of lower gain and deeper bias.

B+ 300V
Ra 33K
Rk 910R
Ck 33uF
Vbias ~~ -4.4V
Ibias~~ 4.8mA
Vo ~~125Vp-p
Zout ~~4.9K 
AV ~~11

above calculated into an Rload = 22K (g1 ckt of 4D22)

so, 2 stages w/ a gain of about 50 or so each, and third stage with a gain of about 10.