Swapping 6sl7's for 12's?

[Nixxuz]

Thinking about using a couple adapters and seeing what some 6sl7s might do in place of the 12ax7s or, possibly, 12au7s in my Yaqin MC13S. Since I went with the KT77s I sometimes feel like I lost some of the tone in the forceful nature of the higher HF and tightness. I'm just spitballing here and having fun experimenting, so I'm not seeking "perfection" or anything. Just playing with semi-expensive tone controls I guess. The Tung Sol 6AK5s I swapped for some GE JAN 5654s brought out a kind of sweetness than made the GEs sound harsh with the KT77s.

In any case, all thoughts are appreciated!

 

[kward]

The 5751 has the same pin out as the 12AX7 but with the gain of a 6SL7. And no pin adapter required. So you might also add the 5751 to your list.

The 12AU7 has much different electrical characteristics as compared to the 12AX7. You shouldn't really sub a 12AU7 into a circuit designed for a 12AX7. However you could look at a 6SN7 as a sub for the 12AU7 if you have a pin adapter socket for it.

 

[Tom Bombadil]

Have you tried multiple 12AX7s? I've found a bit of difference between brands, new vs old.

 

[Nixxuz]

Have you tried multiple 12AX7s? I've found a bit of difference between brands, new vs old.

I've got 4 different types of 12ax7s in my analog, (vinyl), chain. NOS and new issue. I've discounted some of the NOS stuff until recently because I hadn't gotten to the really crisp sound I wanted. Now I'm trying to use that roll-off to tame it a little and strive for better tone. As I said, the 5654 GEs were great when I was running EL34s in the power stage. Now that I've got KT77s they are almost too bright. I'm still experimenting of course.

 

[primosounds]

Thinking about using a couple adapters and seeing what some 6sl7s might do in place of the 12ax7s or, possibly, 12au7s in my Yaqin MC13S. Since I went with the KT77s I sometimes feel like I lost some of the tone in the forceful nature of the higher HF and tightness. I'm just spitballing here and having fun experimenting, so I'm not seeking "perfection" or anything. Just playing with semi-expensive tone controls I guess. The Tung Sol 6AK5s I swapped for some GE JAN 5654s brought out a kind of sweetness than made the GEs sound harsh with the KT77s.

In any case, all thoughts are appreciated!

You also need to be aware of the current use of the octal tubes which maybe different if the ax7 is wired at 12.6 or 6.3. If they are wired as 6.3 then the current use is about the same. But as a whole adapters while they allow you to try different tubes are not really the same thing as properly wiring the tube. It is seldom the case where one tube can be directly substituted by a different tube without other changes to the circuit. There is also an issue of signal loss through the adapter which can be noticeable.