Tube amplifiers

With a tube-based preamp in place, I am somewhat tentatively taking a look at some tubed power amplifiers to go with it.  I’m nowhere near a buying phase yet (unless an incredible deal comes along), but it helps to get familar with brands, models and price ranges for completed sales, to have a point of reference.

The tubes have a specific lifespan, so that is the first consideration.  How many output tubes will the amp have, how hard are they to find, and what do they cost?   Are they common tubes, or something unusual (which can be both good and bad)?  The small signal tubes have a longer lifespan but there, too, eventual replacement will be lurking in the future.

Next, what about power consumption?  At idle, tube amps can use a lot of power.  Some days if I am working from my home office, I may have the power amp running twelve hours per day.  If it is idling at 500 watts, that is quite a substantial amount of power…and heat.

Finally, to get a hefty amount of output power, will I need to find a larger stereo amp, or switch over to monoblocks?

As for brands, there are a lot of choices. Given my experience with Conrad-Johnson, I may want to stick with their products.  I passed up the MV60SE that the seller of my preamp had, but I didn’t feel 60 watts per channel was adequate for electrostatics.  It still might be a good entry point.  The Classic Sixty is another, similar model that would fit the same bill.  I really like the Premier 140, or even a Premier 11, the latter being around 70 watts per channel and the former being around 140/channel.

VTL (Vacuum Tube Logic) is another manufacturer I’ve kept an eye on.  I had to pass by a ST-150 that was several years old, yet was hardly used.  One neat feature about many of VTL’s amps is that you can use the amp in two different modes–an ultralinear tetrode mode that is faster and more accurate, or the triode mode which has the “tubey” characteristics that many like, albeit at half the output power.  A rear panel switch changes modes.

One other interesting option is a VTA M125 monoblock–it is a kit-built amp based on the old Dynaco circuitry, yet greatly enhanced.  It, too, has a dual-mode switch, and it can also run in a half-power mode with only two output tubes vs. four.  The only drawback is that these are built on a raw chassis and have no cages, something I would prefer to have with an amp.  I tend to buy most of my equipment second hand, and pricing these out, the cost is about the same as some of the other amps I have mentioned above.

Given the few drawbacks of tube amps, I sometimes wonder if sticking with a better solid state amp might be a better choice.  My current amp needs some new capacitors and a couple of small modifications which would make it into a top notch amp.  Likewise, I can get ahold of a Conrad-Johnson MF-2300 that gives me about the same amount of power I have now, but would maybe be a better match to my C-J preamp.