preamp inverts polarity

@geoffkait
Yeah, I can hear polarity. Been playing with that a while on my amp.

@cleeds
You kinda pointed out the point I was making. You can only decompress air to a vacuum. But you can compress air until it begins to change phase. Sea level air pressure is about 16 psi. That's the absolute limit to how negative a wave can be. But it’s not very technically difficult to produce 32 psi or even 50 psi pressure waves. That’s, in short, why air is single ended, why it’s natural character of distortion is low and even order, and why single ended amps best emulate the character of the medium sound travels through.

“why single ended amps best emulate the character of the medium sound travels through”

This is very intriguing. Does this have to do with how the electrons move to create voltage to drive the speakers or something else? Hard to connect the dots.

Hey, I’m going to clunk your heads together. You do not (rpt not) obtain a vacuum by compressing air. You suck the air out of the container to produce a vacuum. A vacuum is measured by no. of air molecules per unit volume. A perfect vacuum would have no (as in zero) molecules at all. Obviously, a tremendous mass will compress air a lot but not (rpt not) completely, which is why air shock absorbers work even for very massive commercial jetliners. PV equals RT. The number of gas molecules in the container remains constant. Hardly a vacuum. In fact there are MORE molecules per unit volume when the air is compressed. A lot more.

geoff, read their posts again...they said “ decompress” air not compress. Either way, you’re correct about how vacuum is obtained. 
I’m still stuck on that single ended amp remark...😁

Kalali,

It’s pretty simple. The bias level in a single ended amp defines how negative a signal it can pull it down. If the source drives it below that bias level, the gain device goes more non-linear and eventually shuts off completely. It’s the electrical equivalent of trying to pull a vacuum in air. Push-pull amps don’t do that unless they’re deliberately mis-balanced. Instead, they transition to class AB and one half of the push-pull does all the work. That's why SET amps have such devoted followers. The way a triode distorts as it runs out of bias is very organic and similar to how air behaves.