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What is the best premp for Atma-Sphere MA-1 3.3 amp?

I am thinking about Atma-Sphere MA-1 amp to drive Sound Lab speakers. I can go with A-S preamps (MP-1 or 3) but I was wondering if there are better sounding or better value preamps that match well with MA-1 amp. I am new to tubes and am concerned about the tube hassle, but it seems that the improvement in 3D and clarity of tubes may be worth it. Any recommendations? I wan to stay slightly below the proverbial "point of diminishing returns."
128x128chungjh
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almarg
9,670 posts
 
...  I felt like I was back in my Electrical Engineering class at MIT 40 years ago.
Awesome! I did my EE studies at Columbia (BS) and RPI (MS). I also have a JD (UConn).

Good luck. Regards,
-- Al

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atmasphere
11,615 posts
 
Of course, X350.5 is giving out 350W at 8 ohms in the frequency range where most music lives and is therefore much more powerful than MA-1. Then the question is whether I need 350W in the flat portion of the impedance/frequency curve if I don't listen at rock concert levels and my room is medium size 400 sq ft. What do you all think?
@chungjh You've put your finger on the issue. ESLs in general have their impedance curve deriving from a capacitance which is intimately involved in the electrostatic principle.

As a result the impedance curve does not reflect on the efficiency of the speaker! In a normal box speaker, the impedance bump in the lower frequency is a common example of how the speaker has a higher efficiency at the resonance of the woofer in the box- and this is seen also as an impedance peak. The higher impedance of ESLs in the bass is not caused by resonance- and so for the speaker to do 86dB at one meter in the bass region takes the same watt of power to do so as it does at 1KHz or 10KHz. Yet the impedance of the ESL is quite different at these frequencies; in the bass the Sound Labs get to 30 ohms and are much less at 1KHz and even lower at 10KHz. If the amp can double power as the load impedance is halved this also means that the amp's power is cut in half as the load impedance is doubled. This is why the MA-1 makes more power than the Pass on the Sound Lab.


Al has already gone over that bit; the one thing not mentioned was the issue of transients which gobble power mostly in the bass. This is why the MA-1 will seem across the board about the same power on the Sound Lab as a solid state amp that makes over 400 watts.


One other thing to keep in mind- while the 86dB number makes most speakers impractical in many rooms, a line source such as the Sound Lab can be corrected by adding about 6dB once you are about 10 feet back. So 92 dB is then more practical. This is exactly the same phenomena where the volume does not appear to increase as you move closer to the speaker, unlike point source speakers.
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chungjh OP
265 posts
 
@atmasphere 

Thank you for the explanation. If I understand you correctly, you are saying that even though Pass has more power at 1 kHZ than MA-1, it is the power requirement at bass that is more rate limiting because transients at bass frequencies makes up much of the amplifier's power demand. Did I get your concept right?

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atmasphere
11,615 posts
 
^^Yes.
phantom_av's avatar
phantom_av
320 posts
 
Its very hard to beat the MP-1 regardless of what other pre-amps you put against it. 

The MP-3 is almost 90 % of the performance and with Resistor and Caps upgrade Atma Provides I'm sure your getting a little closer.


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