Best Tube Amp/Preamp combination with Quad 2805s

Between the Primaluna and ARC I would take the Primaluna even though I am not a fan a Chinese tube amps.

The RM-100 is a better suggestion.

Also, since the 1950s, ESLs and OTLs have been the 'match made in heaven'. This is because ESLs are a Power Paradigm device, see:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

Now if you read the article you now know that if you mix the two technologies, Voltage vs Power, you get a tonal aberration. The ARC is more Voltage than Power (uses a lot of feedback); you will find it does not play bass on the Quads very well.

The Modwright is on the Voltage Paradigm. So on the Quads it will not make the bass that the speaker is capable of. You will have far better luck with the VAC.

Well, *I* prefer our amps, so you will have to take my preference with a grain of salt.

Philipwu, now you see why the conflicts of these two paradigms has spawned the tube/transistors debate; yes, nearly all transistors are on the Voltage Paradigm, but not all- the Pass First Watt amps would be an example.

The Quad has a pretty variable impedance curve- which causes a lot of transistor amps to be bright in the highs and not play a lot of bass. If you investigate, you will find that most people that get bass out of Quads and transistors usually have the speakers only a couple of feet from the wall. This gets them some bass reinforcement, but only at one frequency.

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!

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.

Bruce, Its not quite as extreme as that :)

You do get some capacitive phase angle. But most ESLs have a matching transformer too, so you have some inductive issues as well. Overall though other than impedance, all ESLs tend to be fairly benign in that regard.

I don't know of an ESL that is 'voiced'. When I look at the older Quads and the Sound Labs, they certainly aren't. In my book, 'voicing' is some sort of frequency compensation that has been introduced to make the device work a certain way.

I do know of an ESL that has tweeter and woofer sections, and is actually equipped with two woofers (where a Quad has only one). This particular speaker (which is not well known and is not an ESL that comes up when people talk about ESLs) only works with amplifiers that have a very low output impedance.

Martin-Logan loudspeakers have a low impedance and for that reason can be a difficult load for tube amps, but even they are not 'voiced' so far as I can tell- if you get a set of ZEROs you can drive them with a zero-feedback tube amp no problem (as long as the amp has the power). So I think the 'voicing' thing isn't, with regards to ESLs.

In recent years (since the ESL63 and ESL57) Quad has been going down the path of lower impedance, much like Martin Logan, in an effort to get transistors to be happier with their speakers. They have so far been more moderate about it than Martin Logan (whose speakers are typically rated at 4 ohms although they are only about 0.5 ohms at 20KHz), I think the newer Quads have been about 8 ohms (meaning their 20KHz impedance is about 1 ohm), as opposed to the old days when they were rated more like 16 ohms. FWIW the Sound Labs seem to come in around 30 ohms by the same measure.