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New to tubes

I have just acquired a new Rogue Audio Cronus Magnum integrated amp, which is my first foray into tubes. The amp is rated 90 watts per channel and I was told by my dealer (as well as read posts here suggesting the same) that tube power counts double when compared to ss. If so, I am a little confused why I have to turn the volume knob much higher (to about 2 o'clock position) on the tube amp than I had to on my old integrated Rotel amp rated at 60 watts per channel to get the same level of loudness when listening to my tt? I never had to turn past 12 o'clock to get sufficient volume from the Rotel. The associated gear is the same, my speakers are 88 dB efficient and I've tried both the 4 and 8 Ohm taps with the same result. Is it normal? Everything seems to be in order otherwise.

Also, is there a good resource you could recommend that discusses tubes in general? Things I'd like to know about are: maintenance--how often tubes need to be replaced, how do I know when they need to be replaced, why and how to clean the sockets; how long I should warm the amp for before doing serious listening; tube rolling (i.e., what are different types/brands of tubes I could try with my amp), etc...

RA has been great with answering my basic questions, but from their one line replies I get a sense I would not get a meaningful answer to all of my questions. And perhaps they shouldn't have to since there is such a wealth of knowledge out there, including this forum.

Thank you.
actusreus
mcfarland
356 posts
 
I thought that the Rogue Audio Cronus Magnum had 55 wpc, using 4 EL34's, 3-12AU7's, and 2-12AX7's. Tubed amps typically have a "warmer" sound to them, so they sound "fuller", giving the impression that they have more power, however, 55 watts is 55 watts/channel, not 60 as in your Rotel. Also, your speakers (?type?) may be presenting a "difficult" load for your amp depending on the crossover and how low the impedance curve dips. Generally, I have found in my usage, that the smaller signal tubes last 9-12 months, or a bit longer, and the power tubes last 2-3 years. You do not need to rebias your amplifier when replacing the small signal tubes. The sockets usually do not require any cleaning, rather the tube pins should be cleaned with a mildy abrasive cloth to rid them of oxydation and manufacturing debris. I trust this helps,
elevick
2,638 posts
 
From my experiences, 12ax7's should last 2500 to 5000 hours, 12au7's a little longer. I never get more than 1500 hours out of EL34's. Also, EL 34's usually don't put out more than 20-25 watts each in Ultralinear and half that in triode. So, 4 tubes (2 per channel) is most likely 55 watts max.

Tube wattage has been stated as double that of solid state but it's a huge discussion in itself-I'm not touching that!

Now, with that said, every amp's volume will be different as to where the knob is as to how much volume. The gain from the phono sections will make a difference too. 9 o'clock vs. 12 o'clock is meaningless. Max volume is not.

For tube learning, google "joes tube lore" and go to sonic frontiers site/anthem and look for "a taste of tubes".
actusreus OP
733 posts
 
Yes, it does. Thank you very much for your advice.

As far as the power rating, Magnum is an upgraded regular Cronus; a Cronus on steroids, if you will. It has 4 KT-90 tubes, instead of EL34, hence its higher power. It has more upgrades as well, such as better power supply and upgraded internal components.

As far as the speaker impedance, my Totem Hawks have a nominal impedance of 6 Ohms and according to the manufacturer, very stable and never dropping below 5.2. The sound is still glorious; perhaps bass a little less tight than before but the highs and midrange simply heavenly.
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