New tubes in Rogue M-180 Monoblocks

I have been using the KT-120 tubes in the Rogue M-180 for about 6 months now. They replaced Genelex Golden Lion KT-88 reissue tubes. In my opinion they sound better than the 88's on every level and I have not noticed any drop off in performance to date. I talked to Mark Obrien before I bought them and he thought they made the M-180 perform its best. Most of what I have read FWIW about the KT-90 is that they were a little thin sounding, but i have nop ersonal experience.

Daverz,

Are you sure about the biasing? I was told by both Mark and Nick at Rogue the KT-120 should be biased at 40 mA, just like the KT-90. Are we talking the M-180 monoblocks or the Cronus integrated amp? The Cronus is to be biased at 35 mA, but the M-180 at 40 mA.

Actusreus, I don't remember who I talked to at Rogue. Maybe he thought I was asking about a Cronus. I'll try calling them on Tuesday to get some clarification.

Daverz,
I emailed Mark yesterday to clarify this. He'll probably respond sometime next week since it's a holiday weekend. I'm relatively new to tubes so I'm not sure how to determine correct bias other than knowing when it's quite off; the sound just isn't right. I've searched some of the old threads regarding biasing, but didn't find much general information on the subject applicable to all equipment. Essentially, the advice is to adhere to the manufacturer's instructions, which certainly makes sense.

In the meantime, how do you like the sound at 35 mA? Did you have them biased at 40 mA long enough to make a comparison?

The KT90 was thin/lean sounding compared to the KT120 in my Apollo monoblocks. Had a KT90 blow up after 1 year of light use -- a nasty short; sparks and a smoked resistor. No such issue with KT120 in the same time period -- that said, it's naive to trust the reliability of any Russian power tube. I've only run both at 40ma. Suppose it might be smart to try 35.

There are some good points to the KT90 sound, and some listeners will prefer them, but I significantly prefer the KT120 9.5 days out of 10. The bass response is more powerful -- and it's not subtle. The KT120 is smoother and less harsh. If this sounds good to you, give it a try. If your system is a bit bass-heavy and/or needs extra sparkle up top, then stay away. Suits my current system. I believe all current Rogue amps -- other than the non-Magnum Atlas/Cronus -- can provide the extra heater draw. My dealer's M180s shipped from Rogue with KT120 installed. They've also got a Cronus Magnum with KT120. EVERY time I've asked Rogue "what about using alternate tube type X that draws Y more heater current" -- amp or preamp -- they've responded "yes, it can handle that". Heck, I run 12BH7 in place of 12AU7 in my Apollos, on top of the KT120.