Pass XA.5 and Maqico Q Synergy

[FlexibleAudio]

Very well said Ken. As I understand it, the Static Induction Transistor ("SIT") invented by Nishizawa from Japan is now taken to a completely new level by Nelson in the XS and .8's and they are truly something special. Interstingly, I have the option to trade my XA200.5's in to the dealer for 12 months at my cost for a pair, if I like the XA200.8's. I pulled the trigger on the XA200.5s due to a phenomenal deal but preserved the option. They have my attention big time but I want to pick my speakers first!!!

From Pass on XS Topology:

Process

We began the work with a group of listeners and upgraded the uniformity of their playback systems with components chosen for the ability to reveal differences between amplifiers. We did not do AB or ABX testing – people lived with prototypes as long as they liked in their own system, and the only changes made were to the amplifiers themselves.

We built sets of modular prototypes which allowed us to alter any given part of the amplifier – the heaviest parts, the heat sinks and transformers and such, stayed relatively static so that one person could easily make the changes.

At the same time we began an examination of the characteristics and sound of some other types of gain devices (tubes and SITs) and also alternative versions of the Jfets and Mosfets which comprise our current products.

The process took about three years. In the first year we had settled on most of the power supply design and the physical chassis and heat sinks, and in the second year we finalized the basic power output stage and front end. In this last year we have been tweaking the front end circuits and the biasing arrangements and values of the output stage.

Harmonic Structure

We paid a good deal of attention to the harmonic structure of the amplifier’s transfer curve. It is well understood that the relative amounts of the various harmonics in distortion characteristic contribute to the perception of audibility. It is generally agreed that concentration of this distortion into the second and third harmonics is best and the reduction or elimination of higher order harmonics is also desired. What is not so clear is the best relative second and third harmonic amplitude and phase.

It turns out that these relations are some importance and that their perception is also dependent on absolute amplitude, the topology of the circuit, the bias of the circuit, the types of devices, the feedback which might be employed, and of course, everything else. However, for a given design, these things can be successfully tweaked into a state which is subjectively preferred by our listeners, and we came to unanimity on the result.
Emphasis on Output Stage

While every part of the amplifier is important, playing with developmental tube and SIT designs, we concluded that it is the character of the power output stage itself which is most influential in shaping the sound of the amplifier. This is not a radically new idea – the output stage does the most work, generally has the most distortion, and is the interface to the complex variable and reactive load which is a loudspeaker.

In the end, we found that adjusting the values for push-pull Class A biasing and also the amount of single-ended bias in the output stage gave us a major improvement. Pass Labs started with single-ended Class A bias in 1991 and current product still uses some of these techniques, but the new design increases the value of single-ended bias by an order of magnitude over the XA series of amplifiers. This bias is supplied by newer, improved constant current sources with tightly regulated values and very high dynamic impedances.

This will be a very interesting decision. I already salivate just reading this stuff.

[Mikado463]

Originally Posted by FlexibleAudio

I recently purchased a pair of Pass Labs XA200.5's and am trying to decide between the S5 and Q5 as the next step in my system plans (described below).

My primary question is will 400 watts of Class A be able to get the most of the Q5's? Will the Pass Amp's be "exposed" by the resolution of the Q5 in a negative way as is discussed so much in various threads?

Paul, I can't imagine your new XA's not being up to the task, along with the ability of doubling down into a 4 ohm load they do so with excellent current delivery. Whether they meet your sonic expectations in driving the Magico of your choice only your ears will know.

FWIW, my local dealer (Overture, Wilmington, De) swears by Spectral amplification driving their Magico line and yes they 'used' to be a Pass dealer as well.

[PlanarSpeakerFan]

A big thank you to Chuck and Paul for the information you posted on the new .8 series of amps. It was captivating reading! Now all we need to do is hear them for ourselves.

Best,
Ken

[PlanarSpeakerFan]

One interesting thing I noticed is that both the XA-160.8 and XA-200.8 are more efficient than their .5 series counterparts. Each of these amps draws 100 watts less power per channel.

Ken

[The Sandman]

Originally Posted by PlanarSpeakerFan

One interesting thing I noticed is that both the XA-160.8 and XA-200.8 are more efficient than their .5 series counterparts. Each of these amps draws 100 watts less power per channel.

Not surprising really, since they put out significantly less peak amps than their .5 series counterparts, at least according to the specs listed (40 vs 48 for the XA 200, 30 vs 36 for the XA 160). Hmm...

[cma29]

Originally Posted by PlanarSpeakerFan

A big thank you to Chuck and Paul for the information you posted on the new .8 series of amps. It was captivating reading! Now all we need to do is hear them for ourselves.

Best,
Ken

+1. Yeah - Great link. I'd like to hear the XA100.8 and compare it against the XA100.5

[PlanarSpeakerFan]

Originally Posted by The Sandman

Not surprising really, since they put out significantly less peak amps than their .5 series counterparts, at least according to the specs listed (40 vs 48 for the XA 200, 30 vs 36 for the XA 160). Hmm...

Thanks Howard. Where did you find the peak amp delivery numbers for the .5 series?

Ken

[The Sandman]

Originally Posted by PlanarSpeakerFan

Thanks Howard. Where did you find the peak amp delivery numbers for the .5 series?

Ken

https://passlabs.com/images/uploads/...xa.5_specs.pdf

[PlanarSpeakerFan]

Originally Posted by The Sandman

https://passlabs.com/images/uploads/...xa.5_specs.pdf

Thanks again, Howard. I'm actually surprised that the .8 series amps have lower maximum current delivery than the .5 series amps, especially when the article states that the power supplies are larger and have up to a third more storage capacitance. Any thoughts as to why?

All the best,
Ken

[The Sandman]

Originally Posted by PlanarSpeakerFan

Thanks again, Howard. I'm actually surprised that the .8 series amps have lower maximum current delivery than the .5 series amps, especially when the article states that the power supplies are larger and have up to a third more storage capacitance. Any thoughts as to why?

If you're asking me why I have no idea and this is not something to speculate on - hopefully we can get a clarification on this from Pass Labs.