Using tube amp with electrostatic speakers.

I was running a 30W (class A) tube amp when I upgraded my speakers to Martin Logan Spires.

While I could get sound out of them, I couldn't really make them sing. And no, my days of listening to rock-concert level sound pressure values are long behind me.

I first upgraded to a 205 W pro amp (Soundcraftsmen PCR800) which resulted in an incredible improvement over the tube amp. I've since upgraded to a pair of Soundcraftsmen monoblocks that are capable of 900 W at 4 Ohms.

Is 900 W complete overkill? The extra power isn't about playing my system loud - it's about better instrument separation and definition at low volumes.

While there are tube amps out there that can efficiently drive ML's, they tend to be in the upper price range.

I find that the best combo for ML's is a tube preamp, coupled with solid state monoblocks.

YMMV. 

I know this is an old thread but it has some very useful information.  I have a question from reading the thread that I hope someone could answer.  Assuming you have an electrostatic speaker that varies in impedance from 2 to 16 ohms (hypothetical 2 ohm hf 16 ohm lf) and you have a tube amplifier with 2, 4, and 8 ohm taps.  Are you better off setting the tube amplifier to the 2 ohm tap to drive the high frequency.  What would be the tradeoff in this scenario for the spectrum at much higher impedance.  Would there be an issue/tradeoff at low frequency (lf) if you used an autoformer and it boosted the impedance at low frequency much higher.

Regards,
Gary

Normally you would use a higher tap. This is assuming the amplifier uses loop negative feedback, which most do.

The feedback will help the amp to boost its output into the lower impedance. Since there is almost nothing for power requirements, it should be able to do this easily. So its really whether you use the 4 or 8 ohm tap and I would start with the 8 ohm tap.

Ralph-  I've been using a MacIntosh MC275 with a set of custom Quad 2805's-  the chinese panels are not well made and I had Kent McCollum rebuild using UK-produced 63 panels, then add all his upgrades. Measurements on the Quad 63 & 2805 show 4 ohm as the low impedance. Measurements on the MC275 show good linearity and very low distortion (for a tube amp) when using a tap where the load equals or is higher than the tap utilized. While I originally ran the Quads at 8 ohms, I switched to the 4 ohm tap and it is very nice. I crossover at the appropriate point for the Quads and supplement the bottom with a Velodyne SW. The PA is a one-off SS design which is very clean and has almost nothing in the signal path- made by Ron Sutherland for me. Does the 4 ohm tap in this case make sense to you?

BTW, I have an unusual collection of ELS's including the original ML CLS pair. I don't mean one of the production models, I mean the original prototypes. Gayle Sanders voiced these to match a set of contemporary STAX ELS headphones as closely as possible. They really are spectacular but a difficult load to say the least. The production models were tamed down and never sounded as good at the original prototypes. Back in the day, I drove them with a Yamaha B-1, a rare beast that could handle very difficult loads and was quite an amp in the late 70's-  all vertical Static Induction Transistors in the output stages.  Speaking of Stax's, I also have a pair of 8x's- another superb and very rare electrostatic. 

Gary Osoba

I realize this is an old thread but it has a lot of information related to the issues of using a tube amp with electrostatic speakers.  I have a question related to the information provided.  It seems the issue is the impedance variation from high frequency hf (low impedance) to low frequency lf (high impedance) of an electrostatic speaker.  SS amps output a voltage for a given input so they will emphasize the hf vs the lf at a given power output because of the impedance variation of the electrostat over the audio spectrum.  From what I gather tube amps deliver constant power over the spectrum but you can be limited at low impedance (if the amp can't drive the load) or at high impedance if the output voltage does not swing high enough.  Please let me know if my understanding is incorrect.
Should you always use the lowest tap on your amplifier (e.g. 2, 4, 8 ohms) corresponding to the lowest impedance of the electrostat?  What is the trade off at low frequency high impedance using the 2 ohm tap.  If you went with the autoformer and it gives you the ability to drive the 2 ohm load what is the tradeoff at low frequency high impedance (e.g. driving 30 or 60 ohms).  Any insight would be appreciated. 

Best Regards,
Gary