Threshold S/500 versus Mark Levinson ML2

Has anyone heard these on electrostatic panels in comparison? We currently have an S/500 I modified by Jon Soderberg running a pair of Innersound Eros and am wondering if a move to the ML2's might be a lateral move as opposed to an upgrade. Thanks kindly for your input.
I don't have directly relevant listening experience, but I see several problems:

1)Not enough power, despite the fact that the ML2's would only be powering the mids and highs. I say that especially considering that a lot of your listening appears to be to wide dynamic range symphonic material. This review of the Eros MkIII indicates that Innersound recommends amplifier power of 80 to 300W, while the ML2 is only 25W. Also, note in Figure 2 that the external crossover provides a boost of several db in the mid-range, which would increase the amount of power the ML2 would have to supply by a factor of more than 2, relative to what it would have to supply if there were no boost in that region.

2)The age of the ML2's (30 or so years) is likely to be a sonic variable that is both significant and unpredictable.

3)Repairs are likely to be expensive, if necessary in the future, and some parts may be unobtainable.

4)I believe that a pair of ML2's in prime condition will set you back upwards of $6K, which seems like a lot of money to invest given the risks I've listed above.

-- Al
well how is the sound with the Threshold? If your not completely satisfied then by all means try the levinson.You should also be open that it might not be gear related. Most look at upgrading and never take into account the most important piece if gear "ROOM".
Comparing those amps is hard-in my opinion they don't share any of the same characteristics.
Thanks for your input guys, especially Al with the detailed and comprehensive response. I do like the S/500 and think that its benefits outweigh the costs associated with investing in the ML2.
I have Fullrange electrostatic panels from Acoustat and I have driven them with several Thresholds and Levinson amps.
I settled for the ML-2 which I found the most satisfying amp overall. I did like the Threshold SA/1's and Jeff Rowland model 7's also.
I would certainly prefer a set of ML-2's over the S/500.

ML2 mono blocks all the way, 20w pure class A all the way to 160w pure class A to 1ohm. But hey the S/500 is a great amp too

Cheersa George
I never much cared for the ML house sound. I own The Threshold S/500 (Series II). Of all the regular Audiogon posters Almarg is one of those I've come to respect the most.
I also am a bit warm towards the ML house sound, but the ML2 is an exception to that. I have had S500 MKII and S300 MkII optical and the ML2 is better for the esl's.

If you want the best out of ESL's even though it's 20w vs 500w it sounds more powerfull at normal to loud listening levels and oh so 3d and sweet compared to the S500 mkII.

If you want to drive dynamic speaker to massive levels then go for the S500. Like I said both great amps but for different reasons, esl's can only handle up to a certain voltage input before they arc/spark, the ML2 is perfect for this, the S500 can over drive the esl's very early with it's available voltage.

Cheers George
George, I hope my praise for Al wasn't interpreted as a slight to you.
Unsound, thank you most kindly.

George and Brian_Eno, not to belabor a three year old thread, but your comments, while probably applicable to many electrostatics (for example, the original Quad ESL, with which the ML-2 is a classic pairing), are not applicable to THIS electrostatic.

As indicated in the Stereophile review I linked to earlier, it has a built-in low frequency amplifier, and uses the external amplifier for higher frequencies, with the crossover point being at 360 Hz. As indicated in John Atkinson's measurements in that review, the magnitude of its impedance is EXTREMELY high from that frequency up to around 8 kHz, when it finally descends below 8 ohms. Its impedance through most of the mid-range region is greater than 50 ohms(!), reaching 137 ohms(!) at 490 Hz.

A voltage-limited solid state amplifier rated at 25 watts into 8 ohms, such as the ML-2, simply cannot provide much power into those kinds of impedances.

Consider all of that in the context of the manufacturer's recommended power rating of 80 to 300 watts for the amplifier used to drive the electrostatic panel. Consider also, as I mentioned in my post three years ago, "that a lot of [the OP's] listening appears to be to wide dynamic range symphonic material."

Simply put, the ML-2, whose forte is delivery of high current into low impedances, is not a suitable choice for use with this speaker, and that is especially true if material having wide dynamic range is to be listened to. Although it should be noted that current capability is nevertheless not an insignificant consideration, given the speaker's highly capacitive phase angles in the treble region.

-- Al
I didn't even notice how long ago this thread was started.:-)
I had no idea it was that old as well, The Eros is a different beast, but with this statment from John Atkinson leads me to think it wants either or neither of these two amps.

Quote: JA" However, the panel's impedance drops rapidly above 2kHz, and is compromised by a severely capacitive phase angle over much of the treble region. end quote"

I still think with that, if you listen to middle of the road, jazz ensemble music the the ML2 or if you listen to rock or full blown classical then the S500, but you will have a good chance of arcing the esl pannels with the s500 as most esl's can only take a voltage swing of approx 30ish volts and the s500 will give a swing well in excess of that.
Anyway this thread is years old and the owner may not even have any of this gear now.

Cheers George
I found that Threshold is relaunching S350e from the official site.
The ML2 is a wonderful amp. but I agree that the power rating may not suffice for your system. electrostatics are notoriously hard to drive and you need more power in my opinion. The Thresholds are also wonderful amps. Between the two, with those speakers, I would go with the Threshold. but, don't forget, there are Mark Levinson No. 23.5's, 20's, 20.5 and 20.6's out there that would have no problem at all driving your speakers and are incredible. There are amplifier manufacturers out there that are very good at what they do. Threshold, Mark Levinson (older models, I'm still not convinced about the newer ML stuff yet), and Atmosphere, Audio Research, Bedini (yes, Bedini), and many, many others are absolutely great. You need to make sure that the amps are clean and have the power and dynamics necessary to drive your speakers.
You need to hear it first, back in the 80's we built this Nelson Pass 20watt class A and it drove a pair of double stacked Quad 57's with Kelly Decca ribbon effortlesly even with Dire Straights Love Over Gold. And the ML2 is way more powerfull and a extra 5 watts.

Cheers George
George, the impedance of the Quads at frequencies below the upper treble is far lower than that of the Eros. See the curve here, and compare it with the one for the Eros III that is shown in the Stereophile review I linked to earlier.

At 490 Hz, for example, the Quad is about 12 ohms, while the Eros III is 137 ohms, with a phase angle that is only very slightly capacitive. At that frequency, given that the ML-2's power capability into high impedances is limited by voltage swing capability, it would therefore be able to deliver more than 11 times as much power to the Quads as it could deliver to the Eros III.

At other frequencies, the Quad never gets above about 33 ohms, while the impedance of the Eros III is far higher than that throughout most of the midrange.

Also, as I alluded to in my initial post above, Figure 2 of JA's measurements indicates that the Eros crossover provides a boost in the mid-range that appears to be on the order of 5 db, which would add significantly to the voltage swing requirements that are imposed on the amplifier.

I don't know how the sensitivities of the two speakers compare (JA measured 88 db/2.83V/1m B-weighted for the Eros, with its crossover set for unity gain). But it seems clear that the two speakers are very different animals, and I would expect that when the manufacturer of the Eros provided an amplifier power recommendation of 80 to 300 watts, that they put some thought into those numbers.

-- Al
Al I go with what you say as well, but you don't mention the nasty phase angle at all from 2khz up and this wants current, like I said if he wasn't a head banger I'm sure the ML2 would suffice and to boot sound better till they run out of watts.
If he's a head banger and he wants to crank it up, the S500 is the one, but it has the potential to arc the pannels very easily. Usually esl owners are not rock lords and do not party with their speakers.
Anyhow this is all moot as he probably doesn't even own this gear any more.

Cheers George