Two questions. What is the difference between the Shelf/stack vs the rack configuration on the Axiom amps?

Secondly. What is the advantage or disadvantage of using an audio rack vs shelving?

Ventillation, cable management, integrated power strip mounting, much cleaner looking front face to room if exposed.

Drawbacks - cost (if middle atlantic) , parts on backorder depending on type.

Rack ears save a lot of space so you can fit more gear in the same vertical space. The gear bolts directly to rack rails rather than sitting on a shelf.

Advantage: Less vibration. A solid rack, like Solid Steel, or maybe even the budget Pangea rack, will improve the sound quality of your system.

Interesting ....
sometimes I think I’m in an alternate universe
Or maybe I’m missing something ... I’ll sleep on it ... Rack = improved sound ...

Ordered 2 sets of the Isoacoustics GAIA isolators for the 100s. Curious to see if it makes any noticeable difference.

Good rack = improved sound quality.

I will probably recess the rack into the wall towards the back side of the listening area. I will leave enough room to keep the rack from touching any of the surrounding walls and add spike gliders to help isolate any vibrations from the floor. All of these features are new territory for me so I am learning along the way.

Is this a tube thing? I guess I can get my mind around that ...
Doubt it would have any effect on solid state ... at least within reason (vibration and sound wise).

From what I’ve read it can have a positive affect on solid state too. Says that capacitors and other internal parts benefit from racks that help eliminate vibrations. Adding isolators to speaker stands or towers is supposed to have a noticeable affect on sound as well. Again just articles I’ve read but going to put it into practice and see if I can tell any difference.

Well I kind of on the fence with tubes ... just have a basic knowledge and no experience in dealing with them. I can see how vibration might inject it self into the signal.

I’m fairly positive everything else is BS.

Nope, it's not BS. Onkyo holds many patents for anti-vibration designs. Here is one:

https://patents.google.com/patent/US7773373

Of note is the following excerpt:

"The function of the vibration-damping structure of the AV amplifier will now be described. With a configuration as described above, when the power of the AV amplifier is turned ON, a voltage is applied to the main transformer 52 and the sub-transformers 53 and a current flows therethrough. As a current flows through the main transformer 52 and the sub-transformers 53, these components vibrate slightly. Moreover, the exhaust fans 54 are rotated by a driving circuit (not shown) to also vibrate slightly. As the main transformer 52, the sub-transformers 53 and the exhaust fans 54 vibrate slightly, these vibrations are transmitted to the component accommodating chassis 45 on which these components are mounted.
Since the component accommodating chassis 45 is fastened to the sub-chassis 25 so as to be partially in contact with the sub-chassis 25 via a plurality of fastening members, the vibrations of the component accommodating chassis 45 are attenuated while being transmitted to the sub-chassis 25. Similarly, since the sub-chassis 25 is fastened to the main chassis 11 so as to be partially in contact with the main chassis 11 via a plurality of fastening members, the vibrations of the sub-chassis 25 are further attenuated while being transmitted to the main chassis 11."

There's more interesting reading below the above excerpt that describes the nasty effects of these vibrations on the audio signal.

Norimasa Kitagawa and the rest of his crew wouldn't make this up. These guys do nothing, I mean absolutely nothing in their lives but eat and breathe this stuff all day and all night.

P.S. I remember reading that Onkyo had a heck of a time with vibration modelling. They'd introduce stiffening in one area only to discover that reflections from the stiffener resulted in more complex vibrations that created more problems. This is one reason a well-designed EI transformer is preferred over a toroidal transformer for power supplies. The EI transformer is less likely to vibrate particularly with a DC component on the powerline.

Ok they state that vibration gets into the audio path somehow ... they don't say how ... guessing maybe connectors rubbing, mag fields interacting, open air inductors moving, poor solder joints?

Next .. Why they are going to these lengths ... is it audible or to get killer specs ...

I just find the whole thing over the top ... The only time amp vibration annoys me is when the transformer audibly vibrates the case. But ... maybe some of you have actually have experienced this.

Certainly any time a powered passive or active component vibrates in an electric and magnetic field, parasitic voltages and currents will arise. Electromagnetic fields are everywhere. In fact, all matter including biological matter, is nothing more than an electromagnetic field condensate living in an electromagnetic field. What that electromagnetic field really is no one knows but it appears to be a practical abstraction that we make use of.

A manufacturer like Onkyo, surviving with razor thin margins, would never add parts to a design that are unnecessary. Rather, they optimize the design and that's a much tougher engineering feat than manufacturers who use 50 pounds of steel for their chassis.

For patent purposes, they only say as much as they need to and no more:

"When the AV amplifier is powered ON, the power transformer 90 and the exhaust fan 91 start vibrating, and the vibrations are transmitted to the lower chassis 82. Then, the vibrations are transmitted also to the signal processing board 88 and the amplifier circuit board 89, which are fixed on the upper surface of the lower chassis 82. Vibrations of the power transformer 90, etc., influence the audio signal being processed by the signal processing board 88 and the amplifier circuit board 89. Specifically, the audio signal is contaminated with vibration-induced noise, which affects the quality of the sound output from the speakers."

I think, but can't be sure, that any parasitic noise detracts from the perceived soundstage and imaging and also leads to listening fatigue. Transformer hum is certainly very noticeable but there is other, less noticeable noise that likely gets to us and we don't even know it.

I give, Mojo. So, are you putting your gear in restraints? 2x’s preference is a good solid rack.
Don’t think that would eliminate any internal shaking but externally it’s tied down

I’ll guess that in any well designed unit it’s just part of the noise floor ...

There is the theoretical noise floor, the noise floor measured in a lab and the noise floor in the final installation. I'd love to see what the noise is generated within a receiver when turned up and speakers and subs are blaring right at it. Then add to that other environmental noise like EM.

BTW, I haven't gone to any special means to shield my gear from any kind of noise. My cables are like spaghetti. The only thing I've done is route power carefully and not stack the DSPs and amps.

Tubes can go microphonic as they age, so maybe...

But the rest I dunno. Far bigger fish to fry when designing a space.

By far ventillation is key. Rest is bonus.

Ventilation! Yes sir! Some tubes more microphonic than others, from the git go.

Frying fish ... never in my house.

Rich, it might interest you to know that something as minor as the length of your ear or nose hairs affects your listening. Andrew said so in his latest video. I have a nose hair trimmer but unfortunately I busted it as I tried to jam it into my ear. So now I'm in a bit of a panic. This could be why I am only hearing 5 violins.

Did it get stuck? And is it still running?

BTW, apparently Axiom will be offering custom Families of Curves under Customize Yours to correct for various hair types. Those with curly hair suffer diffraction effects throwing off the imaging something fierce.

Good luck with your nose and ear hair situation.

Think about it for a second. Let's say you have an amp whose case is poorly damped and made of thin metal. Now, compare it to the same amp in a well damped, heavy gauge metal cabinet. Do you think this difference would effect sound quality?

I think so. Resonances make a difference. Racks have an effect on resonances of components. So do the feet on components and racks.

Remote locate the rack from the sound source. Preferably in a ventillated closet. Use Harmony companion for components.

Nice choice is DWR series from middle atlantic. But pricey.

Dont need to see rack at all. This one mounted with heating zone manifold. Not Pretty! But cool and tucked away.

What kind of IR repeater do you use? Also, where do you typically hide the sensors? I would imagine somewhere near the screen.

The one on amazon for 20$ or so. Rebranded under many names.

Same as this. Rock solid and plug and play. Then you can grab a harmony 665. Good to go.

https://www.amazon.com/BAFX-Product...R+Repeater&qid=1618434706&sr=8-1

Use a 3.5mm stereo extension cable to front wall behind display or screen and mount on bottom edge.

Nowadays the Harmony companion (149$) is the way to go. Wireless to a rack to a blaster hub and comes with a remote blaster lead. You need an extension cable for it if you want to extend across your room to the display or pull into PJ conduit and set on to of mount. Enables full control of components via APP. So, if you need to get into a wierd menu you dont have to run to the rack and back to display to see what happened with the standard IR remote.

If controlling a PJ 12v trigger is option off of AVR instead.