What are the weak points of Pass amps and pre-amps ?

I remember running a Yamaha 1970s CA 1000 integrated amp with 15 watts Class A switch.  It got rather warm but it did sound superior to the Class A/B 70 watts (about).  The 15 watts sounded more musically involving, smoother and quieter than Class A/B.  

I own an EAR 890 which is 70 watts Class A.  It gets burning hot on the chassis and transformers after 30 minutes. 

I now use a pair of monoblock 130 watt tube amps running Class A/B.  It is a voltage regulated design which runs so cool that after 2 hours, you can place your hand on the transformers which are merely warm.  Plus the sound is superior to the EAR 890.  

I don't think there is an advantage running Class A over Class A/B, depending on design.  The cost of powering Class A and the heat are definitely a consideration.

Are Pass amps somewhat 'lazy', not quite fast and dynamic enough ? 

Owned Spectral electronics for 20 years. Hyper detailed, bright, finicky about setup, the latest SV30 pre amp did not want to play well with my Manley Steelhead or Pass XOno phonostages, DMA 360 amps had a large "thump" at turn on.

Switched to Pass in 2016, Extremely happy with Pass.

Pair of XA160.8s and XP20 linestage.

Dead Quiet. No thumps, buzzes, hums, plays well with others.

All the detail that the Spectral had, but smoother, a little warmer sound, Bass is better, deeper, more textured. Mid range is closer to Live. Highs are not bright and harsh. Can enjoy for long listening sessions.

Yes, they do run warm, but not a problem at my place. At my dealer, in his large, but closed room, it gets stuffy. At 140 lbs. each, they are staying where they are.

Better equipment out there? Of course, to each individuals preferences. Pick what you like. For me, the Pass gear is a bargain and hassle free. Do not see myself looking for better gear. I am off the merry-go- round.

I love Pass and used different mono amps and power amps of them in the last 8 years of time. I choose products based on their DNA. I think they created stunning amps and very good preamps. But I prefer their amps.

When you work by Tru-Fi you want to use all the aspects/properties of sound at the max. The 3-dimensional sound stage is an aspect/property of sound. I have compared many amps also regarding this part. We create a huge holographic stage thanks to the stage DNA of Pass Labs.

Pass Labs is also able to create a very deep, wide and high stage. Diversity in height we call a High-End ++ property. When an audio system can reveal the differences in height of both voices and instruments the harmonics change of a recording.

When we use amps who are not able to reveal diversity in height we always hear a much lower level in the layering of the sound. The limitation Pass Labs power amps and preamps both own is a limited level in the individual focus of instruments and voices. I had many conversations about this with Desmond Harrington (President of Pass Labs) and he was aware of this.

You can adapt it with cables and a source as well. But when we use preamps who own a superior level in intimate focus it becomes clear that it has a huge advantage. It creates a much more lifelike palpable image of voices and instruments.

That is why I want to do presentations with Conservatorium students at audio shows. To let people experience what intimate focus of voices and instruments is and does. After that, I will give a demo with a Tru-Fi system. So they will understand that it is just like in reality.

The first Pass Labs I bought were the XA-100.5 with an XP-20 in 2009. But later I preferred the X-series. I find out that using the right source and cables it has more advantages compared to the XA-series.

It has a little more space and details in the high frequencies. And I also prefer more control in the low frequencies with the X-series. When I bought Purist Audio Limited Edition power cables I became the same level in layering as the XA-series. But with more details and control.

At the end, I will go for the XS series. The extra current will be enough!