Question about tube rolling in MC225

[Charles Turner]

I have the bug to try some NOS tubes in my MC225 amp...I have relatively new EH7591A power tubes but the others are a mixed lot. Tubes are (1) 12ax7 (2) 12au7 and (2) 12bh7. I'm guessing the 12au7s would affect the sound the most but I really don't know.

I'm not planning on anything too expensive...maybe some nice RCAs...but I was wondering if these are the tubes to start with?

I listen mostly to jazz (vinyl) thru 1976 Cornwalls with ALK crossovers.

thanks

[dp1954]

The tube that seems to make the most difference in my 225 is the 12ax7 slot. I have tried mullard, amperex, telefunken, tung sol and tungsgram in this slot. To my ears the tungsgram sounds the best. Really nice extended highs, good mids and great bass. Second to my ears was the amperex. YMMV.

Dave

[joshnich]

I would agree, the 12ax7 slot makes the most difference to my ear as well. I have not had the Macs in the system for a while so I will have to take a looks to recall where I ended up. In regards to the power tubes. I have used the 7591A's as well as NOS 7591's both the collar and coin based varieties. A little more oomph from the A's and a little more detail with the NOS. Havent heard the new JJ 7591s but have heard good things about them.

Josh

[tidmack]

Lame question. . .but what does the term "tube rolling" mean? Is there some prep that needs to be done to the tubes before they're installed?

Jeff

[joshnich]

It just means to try out different brands of tubes. Some do sound a little different than others - depending on the equipment and the tube and what it is doing. I would say that on a scale tube rolling is pretty minimal as to the effect on the sound. That doesnt mean that it isnt fun and rewarding to play with if one is so inclined.

Josh