DHT Tubes

[eeyore]

Just wondering if there is any lists available for DHT tubes? I am looking for a range of DHT for both input and power stage for a SE amp. Thanks.

[andyjevans]

I've used a lot of DHT small tubes and the interesting ones are:

Input single
01A
26
30
30sp (VT-67)
X99
1E4
1G4
1H4 (=30)
5676

Input double
3A5
1J6

Input or driver
112A
31
10Y
VT52

Driver or output
71A
45
46
47
49
50
1624
183/483


Output
2A3
6B4G
300B
211
845
572
811
2E22

[nhuwar]

You forgot the 813, 100th, 450th and the gm 70.
But i'm sure there is more then that.

Nick

[El Zombre]

Any way to tell which tube is DHT from a tube manual?

[nhuwar]

It should say directly heated or indirectly heated on the spec sheet.

Nick

[andyjevans]

You can identify a DHT from the pinout, which you can find on many sites like duncanamps. It will have only four connections 1=plate/anode marked A or P
2=grid marked G
3+4=filaments (plus a centre tap in some cases) marked F

Indirectly heated tubes have a cathode (kathode) marked on the pinout as C or K

The anode may be a top cap.

One useful fact is that many UX4 tubes are DHTs (though some are other things like diodes/rectifiers). DHTs however can be UX bases (and UX5, UX6, UX7 bases for DH pentodes and the like which can be wired as triodes), as well as octal (1J6), loctal (3B7) seven pin (3A5) and bare wires (5676).

I can't think of any ordinary 9 pin DHTs except, I think, DC80 - maybe somebody else knows. Andy

[El Zombre]

Thanks for the info.

[eeyore]

Wow, thanks very much for the list, it would be a great starting point. It is just so tedious going through the RCA Manual/Duncanamp pages that I thought that someone out there might have a page listing the various DHT! Thanks again!