TUBE GAIN

Yes the 12AX7 will outperform the 6922 in your scenerio. The 12AX7 has a amplification factor of 100 whereas a 6922 has a factor of 33.

GE explains the amplification factor as is the ratio of a small change in plate voltage to the small change in grid voltage when the plate current and all other electrode voltages are maintained constant.

The 7025 is similiar to the 12AX7 (AF of 100). Of course, it will have adifferent signature than the 6922.

THANKS FOR THE EXPLANATION.

If you prefer the gain of the 6922, you can try using 5751 instead of 12AX7. The 5751 is a direct replacement with an amplification factor of 70 (not as low as the 6922 but still better than 100). Besides, all of the 5751 I have tried sounded fantastic.

Arthur

The 12AX7 does have higher output but for the same reason it is also noisier.

HI,
THANKS FOR INFO I WILL ORDER SOME 5751 TUBES TODAY.

I would check with Quicksilver first.

5751 are not drop in replacements for 12AX7 in all applications.

Indeed, it would be best to check with Quicksilver first. But keep in mind that some designers will object to you tampering with their perfection, despite the fact the swap will not damage the circuit. The two types are too similar for dire consequences to result (tubes have very loose tolerances anyway). The amp will simply not sound exactly as the designer intended it but, as the owner, which sound is better is for your ears and system to decide IMO. Just like rolling tube brands or sending your amp off to have mods done to it by a third party.

However, I do want to state for the record that using a 12AX7 in a circuit designed for 5751 is NOT a good idea. But the reverse is technically ok, if perhaps not subjectively so.

Arthur

THANKS I JUST REPLACED A 12ax7 WITH A 12at7 IN MY PHONO PREAMP AND THAT SEEMS TO DO THE TRICK.
YOGIBOY

IMO foget the 5751...NOS 1960s Mullard 7025!!!

I JUST PUT A SYLVANIA NOS 12AU7 IN AND IT IS THE BEST I HAVE HEARD YET.THIS TUBE WAS MADE IN 1952.HOW COULD SOMETHING THIS OLD OUTPERFORM ALL THE OTHERS I USED?

Why all the shouting? You woke me up.

Hey, you were snoring so loud I had to do it!

Because back in "the day" people took the time to build much higher quality products than today. Some of the most sought after NOS tubes(ie: TungSol JAN CTL/6SN7GT round plates, Siemens pre-1968 CCa, Telefunken ECC803S, Sylvania JAN CHS/6SN7W tall boys) today were built either to military or telephone service(usually German) specifications back in the 40's, 50's and early 60's.

Sorry.