Rogue Owners Unite

Wow, KT 120s for Zu. Thats a lot of power. Any issues with tube related noise out of those super efficient speakers?

The M120's run so hot because they're a cathode bias design. It's tough to combine high-power cathode bias and PCB without issue. Such a configuration is better served by point-to-point wiring.

The current model Rogue amps all use fixed/adjustable bias and thus provide higher power output with lower heat. They're extremely reliable, and sound excellent. The only operational issues I've ever heard of from the current models were due to bad batches/runs of New Sensor output tubes (particularly the EH KT88 a few years back). I had an EH KT90 short out 2 years ago. The KT120 is a far better sounding tube, and has proven reliable.

As for combining lots of power with efficiency, I run KT120's in Apollo monoblocks (very high gain/sensitivity, and almost 300 Watts/ch) into true 96dB/Watt speakers (not from an overly optimistic dB/Watt rating like some). The amps themselves (with preamp muted) are dead quiet. My preamp is high gain (> 20dB) so it contributes a tiny bit of tube noise, since the downstream gear is so highly sensitive. The vast majority of noise comes from the MC phono stage, and of course there's a big difference here between various makes/models. Mainly, you just have to watch overall active system gain vs. speaker sensitivity. An Atlas with Zu Omens shouldn't have noise issues unless the upstream gear is just wacky.

Roscoeiii,

The Omen is 97dB SPL @ 1W at 12 ohms; connected at the 8 ohm tap it's probably about 94 db. Sitting far-field, I'd guess that at my usual 90 db listening level the amp is cruising at about 5 watts, with 10db peaks asking for about 50 watts, which leaves about 3db headroom.

WRT noise- dead quiet with my ear at the speaker at the above listening level through the line level input (better than the old amps), with some hum and tube rush from the phono input (90's Planar 2 and new Elys 2).

With good tubes, the Rogue 99 magnum is very musical and refined.

BTW, Zu has a sale on the Soul Mark.II until 4-15. $1995.

Rmar, what tubes are you using in your Rogue 99? Also what gain setting do you use.

Jperry,

Short answer- This preamp really needs NOS tubes in the line stage.

I'm presently using what are suppose to be 60's Russian 6sn7's. I could live with these, but I asked Mark at Rogue Audio (how cool is it when the CEO answers the phone!) to send me a quad of Sylvania 6sn7's when they become available, and I'll keep the Russians as backup.

I put 40 hours on a quad of new Sino 6sn7's (long story) but that's all my ears could take. In my system, with mostly not very well recorded material (50's and 60's blues, R&B, and R&R) they sounded...harsh and two dimensional.

The phono board came with what might be Siemens or Phillips 12ax7's (triangle etched in the base at the center between the pins) in the first gain stage, and Sylvania 5963's (or 5814's) in output stage. I suspect that these were the original tubes from the year of manufacture (about 2000).

I checked my tool box (I'm a retired musician) and put in a pair of NIB 70's RCA 12au7's with good results. I also tried a couple NIB Amperex (yellow box made in West Germany)12ax7's in the first stage, but haven't had time for critical listening of that change yet. Those changes did reduce the noise slightly. I also have about six RCA and Japan NIB 12ax7's on hand, but I'm getting pretty tired of playing with tubes, and ready to get this sorted, and start paying attention to the music.