Best Tube Amp For Sonus Faber? Or Pass XA-100.5? $6-7,500 Budget, Purchasing Used.

The ARC Ref 5 preamp is not a great combo with any Pass labs poweramp. We auditioned it with different Pass poweramps.

The limitation is based on the fact that stage depth and width is not like other pre amps are able to create.  It makes the stage less deep and wide. But also in speed and timing it is not at a reference level. Beside this the level in details is also limited. We could proof both in details in the high frequencies and even in the layering in the middle frequencies that they ARC Ref 5 was not able to show the these information we could create.

Both XP-20 ( which I owned for 2 years) and the ARC Ref 5 preamp are also limited in individual focus of instruments and voices. 

This means that they are both not able to create an intimate and physical image of voices and instruments.

I had different conversations with Desmond Harrington about the lack of individual focus of voices and instruments.

You need to understand how voices and instruments are being projected into space and how big they are.

I created Statement Audio Pro measurement what brings any Pass Labs poweramp to a superior and new level.

It creates a superior level in details but also in diversity in sound. There are so much more layers compared to the XP-20 and ARC Ref5.

I can create an even higher level about 6 times each year. We are at a level now that the energy of instruments can be felt separately. And even the energy of instruments can stand in a different perspective of depth.

The acoustics limits the quality of a poweramp so much. Without roomcorrection it is not possible to create this stunning level we can achieve at this moment.

We also can play a lot louder in pure class A with Pass labs X-series amps compared to the XP-20.

Now we have ideas to use conservatorium students to explain people what diversity in sound means and does with our emotion. We want to use instruments and real voices to show people how small and direct they are in real.

We can proof now that with Statement Audio Pro music comes so much closer to how music sounds in real. We are born perfectionists and we want to create the best level in realism possible.

I can create an even higher level about 6 times each year. We are at a level now that the energy of instruments can be felt separately. And even the energy of instruments can stand in a different perspective of depth.

@nightfall , sorry JC, once bo stumbles onto your thread, it is destroyed with mind-numbing audio mumble jumble.
It is akin to termites stumbling onto your home.

Did you get your VAC amp yet?
Which model did you buy?
What do you think?

Since nobody knows what 3D sound is, nobody knows what "real" sounds like, nobody appreciates diversity, everybody ends up hating his or her system, everything except what Bo likes is 2D and non-diverse, and we’re all ignorant, just do yourself a favor and buy Pass, Monitor, and Secret Sauce from Bo--all of your audio woes will be healed for life and you can die happy. Something like that, unless my decoder ring is broken.

nightfall, 
Pass XA-100.5 would be a great option. Also consider some McIntosh SS amps or integrateds such as the MA7900, MA8900, MA6700 integrateds or the MC350 stereo power amp. McIntosh and Sonus Faber have good sonic synergy together.
I've heard your speakers driven by one of these McIntosh amps before at the store and IMO they sounded great together. 
AR amps would be another good option for your speakers. 

I also heard your your speakers driven by the Musical Fidelity Nu-Vista 600 integrated amp before and I thought they were paired very well together. 
Speaker cables also need to taken into consideration in getting a perfect match with your equipments. 

Some Lamm and higher end Primaluna would be a good option for your speakers.

A tube creates distortion, what it does it gives the whole frequency range a colouration.

The emotion of music is inside the music, not inside any audio system or even tube. So you need to understand first how humans experience the emotion of music.

When you only focus on the most important part of our emotion and also music ’DIVERSITY’ it becomes clear that layering in the whole frequency range is by far the most important part to feel the emotion of music.

This means when a system is able to create a higher level in diversity this system will create more emotion during listening. A tube does not create more diversity. It creates a pleasant sound many people like.

Many people in audio have no idea how limited the level they are able to reach of each single part in an audio system. They created their audio system by trial and error and believe that they created their system by personal preference.

But when you have no idea why the stage and sound is what you hear, your system has been created by trial and error. This is nothing more than audio gambling.

Your audio system is being created by all the different properties of each single part in your system togheter including the acoustics.

The acoustics are the biggest part what influences your sound and stage. That is why I did most research in this part. People have no idea how much details and information gets lost.

People think and work like it was 1980 in audio. Mann wake up, it is 2017. You need to learn to look further to create a superior realistic level in sound.

When you want to understand why the stage and sound is what you hear you need to be able te know all the different properties of each single part in your system.

But........even that is not the whole part.

Smog, high frequency noise, magnetism and even more influences the sound and stage negative.

That is why you only can use a very small level in quality of each single part of your audio system. The level in accuracy is very limited. Buying more expensive audio part will not solve these problems. Even buying tubes will not solve this.

You need to understand where and how you loose the diversity in sound.

When I visit an audioshop, new client, distributer or show it feels like I go back in time 20 years ago. And I hear and see often that they still do audio the same way as when I started to work in audio.

It is difficult to believe and understand how less audio is grown in these 20 years. It is as people have been sleeping all the time.

When you want to able to controle audio and sound you need to learn to understand how it is being build. And first of all you need to understand how voices and instruments sound and how they are being projected into space.

But when I visit new clients, audioshops, distributers and audioshows the facts proof that their systems sound so much different than how voices and instruments sounds in real.

This is based on the fact that all these systems are being created by trial and error. And not even one single person can tell what the different properties are of each single part in thier system.

I asked to all these people: do you understand why the stage and sound is what we hear? No one could answer it. It proofs that the systems are being created by audio gamling.

Beside the fact that the systems are being created by trial and error, it also proofs for me very easily that all the systems are incomplete.

This means that all the systems are missing essential parts on which sound is being build. Each single part influences our emotion.

So all the systems have a lower level in emotion and realism. People need to start to focus on music again.

Many audio systems have been created by thoughts of people and endresults of trial and error. But at the end it has nothing to do with how music should sound.

Without music there is no audio. But.....without audio there is still music.