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Best tube amp for electrostatic speakers

For over 35 years I've almost exclusively used either ribbons or electrostats with solid state amplification and have been generally happy with the sound. Over the last several years, though, my hearing has become somewhat degraded and more sensitive to certain frequencies. The frequencies which seem to cause the most discomfort occur in the 1400 to 1900Hz range and come across as "bright" to my hearing. After researching this matter and having been given some expert advice, I've decided to pursue the idea of replacing my present amplification equipment with tube based gear.

The purpose of this post, then, is to solicit advice regarding the best approach to making this decision based on the following information: the current basic equipment is Shanling Solid state CD player, Peachtree Audio Nova used as preamp, two DBX 1531 EQ's to help compensate for age related hearing loss, Peachtree 220 amp, Silversonic T114 cable and Martin Logan Ethos speakers.

The listening area is our living room measuring 15 by 22 feet with my listening position 16 feet from the plane of the 2 speakers which are positioned 11 feet apart measured center to center. Located between the 2 speakers is an entertainment center which is about 9 feet wide. My listening interests are varied from solo guitar and light jazz to occasional orchestral music. I don't generally listen at high volumes and am not particularly interested in strong bass except for the rare action movie background.

Unless not advisable for some reason, I would like to keep the Peachtree Nova as a preamp because of the significant latitude for source connection and what seems to have a decent internal DAC. If this option would substantially defeat the purpose of the intended modification I would work around it. I can no longer deal with sounds that are "bright" which I now find uncomfortable but detailed sound is very important.

So, the questions are: is the move to tubes the best option and, if so, what might be some reasonably priced amps that could accomplish the goal. This, of course, would take into consideration room size, etc. for determining power requirements. If there are other more practical and less expensive options to consider, I would appreciate that advice as well.
broadstone
almarg's avatar
almarg
9,670 posts
 
Regarding the measurements cited in George's two posts just above, I would emphasize that the frequency responses and rolloffs that are described apply to electrical signals at the amplifier output/speaker input, not to the acoustic output of the speaker. As I said earlier:
01-14-15: Almarg
... while it is true that when working into an electrostatic such as the Ethos the use of a tube amp, especially one which uses minimal or no global feedback, is likely to result in voltage vs. frequency characteristics at the input terminals of the speaker that are less flat than would result from the use of most solid state amps, it by no means necessarily follows that the frequency response characteristics of the acoustic output of the speaker will be flatter in the latter case. As can be seen in the comments by Ralph (Atmasphere).
The successful pairing of tube amps with electrostatics by many experienced audiophiles, as can be seen in system descriptions and posts here and elsewhere, confirms the importance of distinguishing between flat frequency response into the speaker, and flat frequency response out of the speaker. They don't necessarily go hand in hand, particularly in the case of electrostatics. IMO.

Regards,
-- Al
atmasphere's avatar
atmasphere
12,164 posts
 
As I have pointed out many times in the past, the impedance curve of an ESL is not the same as an efficiency curve.

With many box speakers the two are the same- higher impedances usually representing resonance, usually a driver in a box.

(If one were to apply this idea to an ESL, it is easy to see how one would think that you need lots of current to drive those low impedances. In a nutshell, it does not work that way with ESLs; they simply are not the same technology!)

ESLs are generally not in a box; their impedance curve is a result of a capacitive function unrelated to resonance.

The result is that the speaker generally needs a constant power characteristic out of the amp rather than a constant voltage characteristic in order to obtain flat frequency response. Constant voltage is that quality that allows an amplifier to double power as impedance is halved (and will generally result in brightness in ESLs). Constant power is that quality where power remains constant regardless of impedance.

There is more at this link:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

While the Power Paradigm pretty well went the way decades ago in mid- and lo-fi situations, it is still very much alive and well in high end. Horns, ESLs, magnetic planars, single-driver full range speakers and various conventional box speakers represent examples of speakers made to conform to Power Paradigm rules.
georgehifi's avatar
georgehifi
10,312 posts
 
Well guys I beg to differ big time, I have Martin Logan Monoliths with the new aluminium vapour deposited panels, and they have a very similar impedance curve that the Ethos have being 1ohm or less in the upper mids/highs.

When ever big tube amps that I have owned or mates have bought around, be it push pull or single ended toplogy are used to power them, yes they sound "nice", but there is a distinct softening in the upper mid/treble region with a big lack of presents and dynamics.

Then swapping over and using my very stable massive high current solid state amps, everyone then hears what's missing during these savage impedance drops, it like someone has opened up a window to the upper ranges and the detail/dynamics that comes with it.

This statement is what a Stereophile reviewer found, with the ML Montis (which have an impedance character almost identical to the OP's ML Ethos speakers) when driven with a highly regarded Audioplax 88 tube amp, .

"This is why Robert Deutsch found that his Audiopax amplifier sounded too soft and lacking in definition."

Cheers George
atmasphere's avatar
atmasphere
12,164 posts
 
Uh, George, please read the thread through (beginning with the title of the thread) rather than just jumping in in the end.

First, this thread is about what tube amps can be used and is not about solid state.

As explained earlier:

Martin-Logans have a very low impedance at high frequencies as you know- we went through that early on. To use any tube amp with them, a set of ZEROs is recommended
http://www.zeroimpedance.com

This eliminates the rather ridiculously low impedance (0.5 ohm) high frequency problem.

Once this issue is dealt with your comments are rendered moot as the ZEROs level the playing field.
broadstone's avatar
broadstone OP
310 posts
 
In the several years that I've participated in these forums these are some of the most comprehensive and cogent responses that I've read. Even though some explanations are stretching my ability I greatly appreciate them and thank you for your willingness to share it.

The pink noise test revealed something that I otherwise may have continued to overlook as an important factor. I described the phenomenon of moving back from the speakers toward my listening position while listening to out-of-phase pink noise (actually, any out-of-phase frequencies) noting that the sound moved incrementally to the right. If I change my listening position to about 5 feet closer to the speakers, then, this migration of sound becomes less perceptible. I know that room acoustics is important but is it possible that it could be so dramatic?

It was pointed out that my system is anything but reference grade or state of the art but, unless I'm missing something, I fail to see why this is pertinent to my inquiry. I know enough about my setup to realize this and if one couples this with the fact that I don't have a dedicated listening room, the challenges are many. Hence, my requests for help.

As an aside, the problem with certain frequencies is little different from when I was using a Rogue Audio Sphinx amp with ML Odysseys. I made the change of amps about 8 months ago and switched speakers only a couple of months ago. It now seems slightly worse for those offending frequencies but, because I used the Odysseys for about 13 years, I may still be adjusting. Also likely is that the Ethos is supposedly more revealing of what's going on upstream in the system.

To answer one question regarding the comparison of live versus recorded music, especially using the piano for reference, we have a piano and, yes, the same notes either recorded or live create the same discomfort. This fact, of course leads me to the conclusion that it is not a component of my system that is the culprit for at least this issue.

Anyway, when I get some help to access the back of my equipment, I'll remove the equalizers to eliminate that variable before I continue with anymore experimenting.
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