I was always intrigued by the MAC valve of the high-end Iwata AB.
I got a $25 Grex quick disconnect with a MAC valve and a couple $1 no-name ones. I’ve tested with my Iwata HP-CS, SAR & Paasche H. I set the psi at the max on my Smart Jet compressor and control the psi on the quick disconnect. It’s SUPER convenient although I still need to develop a feel for setting the psi with the MAC valve.
The worst part is that I’ve noticed zero difference between the $25 one and the $1 one.
I quite like the MAC valve as well. I bought one from H&S for $20, didn’t know they were available for a lot less. The H&S one is quite small and my only problem when I first got it was remembering that it was there and I had adjusted pressure. After reducing pressure, spraying detail, cleaning airbrush and stopping for the night wondered why my AB wouldn’t give me a broad spray at the next session. DOH! Where’d you find 'em for $1?
Amazon! I’ll buy more. I’ve been using a quick disconnect for a long time. A quick disconnect with a built-in MAC valve makes airbrushing so convenient. Since I don’t need to adjust the psi on my compressor any more, I put it under my painting desk.
Okay, what is a MAC valve?
Micro Air Control (MAC) valve.
if you have a quick disconnect and MAC valve combo, you can control your air brushes PSI at the valve instead of at the compressor. EXAMPLE: http://www.amazon.com/Airbrush-Quick-Release-Disconnect-Coupling/dp/B004KNHGR8[](http://www.amazon.com/Airbrush-Quick-Release-Disconnect-Coupling/dp/B004KNHGR8)
Thank you for asking the question, Don! 
sounds like a pretty good gizmo to have. I’m always having to bend down to adjust mine on the floor…which ain’t gettin’ any easier for me as the years roll on.
I used to put my compressor right next to my spray booth to easily reach the PSI adjustment knob. My Iwata Smart Jet is relatively quiet, but when it’s on, it vibrates and makes some noise. Now that it’s under my desk, I get more desk space and no vibration.
The quick disconnect + MAC valve has given me the best bang for the buck.
I put my Smart Jet on a rubber patio paving square. I was putting them down in back yard, and it looked like it would do the same job as those rubber machinery pads, but was much cheaper, a buck for a foot square piece. It did a great job of damping the vibration.