Which Octal equiv. for 12AX7 - 5751 - 12AT7 - 12AY7 - 12AV7 - 12AU7 - 12DW7 ?

[kagliostro]

I'm looking for octal equivalents of this noval tubes

12AX7 (gain factor 100) may be 6SQ7 ?

5751 (gain factor 70) may be 6SL7 ?

12AT7 (gain factor 60)

12AY7 (gain factor 45)

12AV7 (gain factor 41)

12AU7 (gain factor 19) may be 6SJ7 (19) - 6SN7 (20) - 6SR7 (16) ?

12DW7 (gain factor triode 1 = 100 - gain factor triode 2 = 17)

Many Thanks for any indication

K

[sluckey]

6SN7 and 6SL7 cover a lot of territory, have totally independant triodes (share no elements), and are pin compatable. I've used both recently with good results. Ampeg likes them.

[PRR]

Prototype for 12AX7 twin is is 6F5/6SF5 single.

12AU7 twin can be 6SN7 twin or 6C4 single or 6J5/6SJ5 single, which is probably 6J7/6SK7 built as triode.

[jojokeo]

I think the SQ7 would be good for a first stage and then go to the SL7 from there. I think the SL7 is more similar to a 12AT7 than a 5751 isn't it?

6SJ7 is a sharp cut-off pentode.
6J7 also a sharp cut-off pentode.
6SK7 is a remote cut-off pentode.
6C4/6J4 are 7 pin med mu triodes.

Where's the resident obscure tube brothers???

[HotBluePlates]

.. I think the SL7 is more similar to a 12AT7 than a 5751 isn't it? ...

Among the 3, there's no exact match the way there is with 6SF5 or 6SQ7 and 12AX7.

The 6SL7 has the same mu as 5751, at 70. The 6SL7 has a little lower plate resistance and a bit higher Gm; this means you'll get slightly more gain with the 6SL7 than the 5751, when using the same cathode and plate resistors.

The 12AT7 seems close, at a mu of 60. But its plate resistance is ~1/5th of the 5751's, and Gm is about 4x higher. So 6SL7-5751 is a much better match.

[tubeswell]

6SC7 is pretty close to a 5751 (or for that matter a 12AX7 - or 6SF5)

Also the triode part of a 6SQ7 has a mu of 100 (gm of 1100 umhos, and ra of 91k @ Va = 300)

[kagliostro]

Many thanks to all you

K