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Atma-Sphere amps with Eggleston Andra II's

I own a pair of Atma-Sphere MA2 Mk2.3 OTL monoblocks that are probably the one part of my system that will staying put for a long, long time. Currently, speakers are Dynaudio Confidence C2's. Preamp is an Atma-Sphere MP1 MkIII.

I'm looking to change/upgrade my speakers. As good as the C2's are, i.e., extremely coherent, very natural and detailed, nonfatiguing, they certainly don't have much "slam" factor. Now, I mostly listen to classical, jazz, and female vocals at moderate levels, but once in awhile still throw on some Cream, ZZ Top, Seger, ELP or whatever that demands some volume and presence in the low frequencies. I have been reading that the Andra II's can provide most, if not all, of the C2's traits but also add the missing lower octave and slam.

My question to Andra II owners is this: will 220 watts of OTL power drive the Andra II's properly? The MA2's can handle 4 ohm loads without difficulty as long as there are no crazy phase shifts. I am mainly concerned about running my amps dry.

TIA.

Bill
billspecfoc
1markr
594 posts
 
I totally agree that the Andras like a lot of power.

However, I'd have to question the need for 500w or more. I'm sure it depends on the amp, but I'm happily running my Andra IIs off of a BAT VK-500 amp w/ the BAT-PAK (250wpc into 8 ohms) and I have never felt that I need more power. They are firing into a decent sized room (25' x 20'). I occasionally listen at levels that average 95db, and on transient peaks, I notice no compression or clipping with this amp.

Perhaps a lot has to do with the amount of energy that the amp is able to store in its caps. The BAT with BAT-PAK stores a staggering 1100 joules vs. 350 joules with no BAT-PAK.

The speakers really do come alive above 85db, guitar and piano are simply stunning, and lifelike vocals to boot.
talon4
185 posts
 
1markr, I agree about the Bat having alot of reserve power. I used to have a Bat vk5i preamp that I was using in my current system and it had an unreal amount of reserve power for a pre. I also agree that the speakers come alive above about 85 db. The 500 watts is what Egglestonworks has said several times in conversation. Your mileage may vary. Stan
french_fries
815 posts
 
i don't know enough about atma-sphere amps or otl tube gear,
but all speakers have impedence dips, some go to 2 ohms for sure. but an amp with 220W should be able to comfortably drive
a wide range of speakers. i've used rowland m-12's (200W), a krell fpb-300, and a levinson 23.5 (200W) as well as the 33H
on the andras- even when they were series-I's- and NEVER was worried about having enough power.
audiokinesis
2,749 posts
 
French Fries,

The Atma-Spheres and other output transformerless tube amps roughly approximate a "current source", unlike most amplifiers which approximate a "voltage source". In English, that means the Atma-Sphere amps deliver less than their rated power into a low impedance load, and more than their rated power into a high impedance load. This is just the opposite of the way most amplifiers (especially beefy solid state amps) behave. In addition, OTL amps typically have a high output impedance (low damping factor) which further makes a low impedance speaker less likely to be a good pairing.

Duke
gregm
3,409 posts
 
As Duke notes (twice) and others have confirmed, you will not get superlative results using yr AS with the Andra. I.e., you'll get good sound -- but NOT what you bought the equipment for.
The music will be refined and s/what lacking in ultimate energy (upper -> mid bass will be too "polite").
With yr amps I would strongly recommend high sensitivity hi impedance spkrs wearing powerful drive units (wide-range). Audiokinesis gives a good recommendation above. Tannoy (prestige series), rethm, horn-loaded models etc would be fine.
The sound you'll get will be outstanding
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