12AD7, the "Super" 12AX7A

[EWBrown]

Behold, the 12AD7:

http://www.mif.pg.gda.pl/homepages/fran ... /12AD7.pdf

This one is a bit too pricey to be put into the "plinker of the day" topic, the 12AD7 is basically a "permium quality" 12AX7, which has higher filament current (225 mA instead of 150 mA @ 12.6V, double that for 5.3V), lower noise, hum and microphonics. Yup, I found one NOS in the great plinker pile :o

Thses puppies aren't cheap, they can go for $50 or more, AES has them listed at around $19, but they are always out of stock. THis might be one of those "lucky finds" at a hamfest or swapmeet, as they aren't all that well known. Yellow_Light_Colorz_PDT_11

/ed B in NH

[erichayes]

Hi All,

According to one internet "expert", the 12AD7 was developed by Sylvania, supposedly to capture a share of RCA's 7025 market. They do list it in their tech manual (in the condensed data section), as does GE, but RCA refuses to acknowledge its existence.

I've never seen a Sylvania 12AD7. In fact, the only ones I have seen were Toshibas in the old Akai M7 and M8 reel to reel decks that came into the country via PXs back in the '60s and '70s with returning GIs from the Viet Nam "police action".

[EWBrown]

I know I have one, perhaps it is GE, NIB, NOS, ETC... at first I just thought it was one of the 12VDC "space charge" tubes until I finally got around to looking it up on TDSL... I should pre-test it and pop it into one of the DIYT35s and see what it sounds like...

I have a 36 year old Akai R2R tape deck (don't remember the model number, might be GX-7 or 707, something like that.. though it boasts "glass and crystal ferrite heads" ) that I brought back home from my all expenses paid vacation (or vexation) over there in sunny southeast Asia. Last time I played it was about 15 years ago... (I wasn't carrying a gun, my "weapons" were VOMs and signal generators). I might have to peek inside, just to see if there is any glass lurking inside.. Hopefully it hasn't turned into another "turd world" mouse condo :o

/ed B in NH

[Blackburn Audio]

There are also similiar super premium 12AX7 tubes made by raytheon called 12DT7, and Westinghouse called 12DF7.

-Matt at Triode Electronics