anyone have experience w/magnum conversion 4 Rogue

Holymackerel, I'm curious why you went from EL34's to the KT90's. I didn't even think that the Cronus circuitry would allow for this substitution. I went from the KT88's (SED Winged C) to the KT90's (EI & EH) in my Stereo 90 and found that the entire musical presentation was more pronounced, especially in the bass frequencies. I thought it was the best tube I ever used until I started to sense that something was missing in the music. After a a month or so, the music sounded congested in the midrange, like some of the music was compressed or missing, like there was a lot of empty space in the soundstage. I went back to the KT88's and I found that although it wasn't as powerful a sound as the KT90, it was a more pleasing presentation to my ears. It was just more musical and palpable and I never went back to the KT90's again. Simply amazing how personal and subjective this hobby can become.

As I said, I was nervous about going to the KT90's. The Magnum upgrade for the Cronus includes EH KT90's. That is part of why they get 90 wpc out of the Cronus. You can actually drop KT90's into a standard Cronus, yes. You can also use KT77's. Rogue also upgrades the power supply, by the way, "to enable use of the KT90's" although the stock Cronus seems to have plenty of juice. I talked to Rogue about the KT90 before going ahead with the conversion. They said they had been very pleased with the results they were getting with the newer EH KT90's. Obviously I won't know until I have had my upgraded unit for for a while and the proof will be whether I have stuffed the EL34's back into the upgraded sockets in three months or not.

On the wilder side, I've even used EH 6550's in my un-modified Cronus. You have to take the top plate off to do this, so I only did it for a short time. Works fine. I talked to Rogue about having the holes in the top plate cut our a little larger to accomodate the 6550's or kt88's for that matter and was told that I could do that, but that I shoud really give the KT90's a try first. So that's what I'm going to do--give the KT90's a try. Will let you know. BTW, if you do try substituting some of these tubes for the EL34's, make sure to re-set the bias first. There is a big difference in the current draw between some of these tubes, but the Cronus can accomodate them, IF you re-set the bias.

Well, I’ve had the upgraded Cronus (Cronus Magnum) for two days now. My first impression out of the box was that they changed the ugly ducking into an exotic beauty. I had them install the black face plate while they had the unit and the KT99’s are a little larger than the EL34’s and their size seems to make more sense aesthetically on top of the unit. It’s got real binding posts now and ceramic tube sockets. I’m told there are other goodies inside, but the question is always, what does it sound like?
I’m thinking right now more break in. It still smells like it’s breaking in. The upgraded Cronus has lost some of the fat in its tone, moving a step toward solid state. It still runs hot. After about ten hours the soundstage opened up to one of the widest I’ve heard out of anything. I use Aerial 6’s for most of my listening and they do an excellent disappearing act. I’m used to the soundstage going three feet on either side. It’s now six feet on some recordings, and I’ve not heard that before. It has in the first two days become more musical than it did out of the box. I’m starting to hear the music again, and the micro dynamics. I’m thinking the amp is more dynamic than I remember it being before the upgrade. I like that part. It’s taking acoustic bass apart note by note. Transients are very quick. This amplifier is in full control of the speakers. I found myself moving the speakers a couple inches out from the walls. To be honest, they are front-ported and I had them backed up to get a little boundary effect, but the upgraded Cronus puts out enough bass that I found myself wanting to tone down the boundary effects from the wall. Verdict after two days: It needs a little more run-in time. I still have not put the EL34’s back in.

I've had the converted Cronus in system for a week now. It is simply a very good amplifier. Powerful, dynamic, and articulate. It is a keeper. If I change my mind in three months, I'll let you know.

I purchased a Cronus direct from Rogue a few weeks ago and decided to get the Magnum upgrade from the "get go". I find the amp to be very musical and envolving and am pleased thus far with the sound of the '90s , along with the NOS Sylvanias they installed as part of the upgrade.