Best Tube Amp/Preamp combination with Quad 2805s

I would like to reinforce what Joe_appierto wrote. Legends can sometimes be a big pain. People who are not familiar with the newer models keep repeating the wrong mantra. The newer Quads (2805 & 2905) can handle more power than their ancestors. In fact, they prefer more power.

Cosider amplifiers capable of 150W or more.

hi Ralph,
may i refer you to an Amp called AMPZILLA 2000 ver.2 Its spec mentioned :100% stable into any load angle 0 to 90 degrees, capacitive or inductive, regardless of waveshape.
is this Power or voltage paradigms? Thanks again.
I've noticed electrical phase & impedence varies greatly especially in electrostatics, will this amp serve better if it is Power paradigm?
Regards.

Hi Phillip, If the amp can double power as the load is cut in half, then it is Voltage Paradigm. That is because the voltage stays constant regardless of the load.

The Ampzilla is an example of that.

The big variation of impedance in ESLs means that for most transistors, they can't make the same power into the bass regions that they can into the high frequency regions. Add to that that the speaker is really expecting the power of the amp to be the same at all frequencies. This causes transistor amps to not make enough bass and to make too much treble as I mentioned earlier.

That is why you generally want tube amps with Quads!

Ralph, this comment is obviously coming over a year since the last post. Nevertheless, if you catch my comment, perhaps you could respond to my question.

You mentioned that the Quad ESLs have impedance curves that vary a lot as a function of frequency. So, rhetorically speaking, why is that diffrent than most speakers?

My question goes to a point that you and Al (Almarg) have made on numerous occassions. Specifically, in order to know what type of amp matches best with a speaker, be it conventional, electrostat, etc., one should try to determine what the designer had in mind when he/she voiced the speaker in question.

So ... in the case of Quad ESLs ... do we know whether the designer intended that the model in question be driven by a Power Paradigm amp or a Voltage Power amp? My sense is that your posts above permit the inference the answer is Power Paradign amps -- not Voltage Paradigm amps. Is that correct??

Perhaps a match involving an ARC type tube amp, which as you observed uses negative feedback to lower output impedance, might be a better match if the Quad ESL is hooked up to the 16 ohm tap (higher output impedance and higher gain too). However, you might point out in response that using the 16 ohm tap might achieve a smoother sonic presentation, but using the 16 ohm tap might be a non-optimal impedance match. That is the back impedance presented to the output tubes off the primary windings of output transformer might be outside the optimal range of the output stage, possibly causing increased distortion?

Your thoughts??

Thanks

Bruce

Bruce, The answer is that the impedance of most loudspeakers relates to how the speaker behaves inside a box, along with its crossover components.

An ESL OTOH has its impedance curve based on a capacitor (IOW, a high impedance at bass frequencies, low impedances at high frequencies). The early Quads had a fairly high impedance at bass frequencies- over 45 ohms. In an attempt to get a little more power out of transistor amps, the later Quads like this one have a lower impedance in the bass, but the shape of the impedance curve vs. frequency remains the same.

As a result many tube amplifiers work better with the newer Quads when a set of ZEROs are employed, due to the lower impedance at high frequencies.

With your ARC, its likely that you would use the 4 ohm tap, but you would have to try it and see- its not always that predictable and you may be better off with the 8 ohm tap.

ESLs, because they are based on a capacitor rather than box resonance, have the same efficiency regardless of frequency so they are by definition a Power Paradigm device. If you drive them with a Voltage Paradigm amplifier, they can wind up being bass-shy and bright because of the amplifier's response to the impedance cuve (which, in most ESLs, varies by a good 10:1 change from lows to highs).

In a box speaker, the peaks in the bass are caused by resonance, meaning that the speaker is more efficient at those resonant points. The amplifier has to throttle back its power into those peaks to prevent tonal colorations (one note bass- bass boominess). As you can see, the principle of operation is different and is why matching the amp and speaker is so important.