This was just posted on Peachtree Facebook page
Are zero feedback amplifier designs like the GaN 1 susceptible to speaker impedance?"
The short answer is yes. The longer answer, for the GaN 1, is that a 4 Ohm speaker load will generate a ~1dB softer top-octave response. Below are the actual AP measurements showing the GaN 1 amp module with an 8 Ohm load (top lines in cyan and green) and a 4 Ohm load (bottom lines in yellow and red). You can see they are flat lines until ~4-5K, then the 4 Ohm load creates as gentle rolloff of about ~1.2dB at 20K compared to an 8 Ohm load.
What does THAT sound like? Many probably won’t even notice it due to their own hearing sensitivity at those frequencies, but some may perceive it as an ever so slightly "laid back" or "polite" presentation.
We do NOT "voice" the GaN 1 to sound any particular way as you can see. It is ruler flat with an 8 Ohm load, but we do get frequently asked "what will MY speakers sound like with the GaN 1?" And below is the most objective answer we can provide.
Unfortunately, what we haven’t figured out how to measure yet is how to chart how open and transparent the GaN 1 sounds. The ear/brain is an incredibly complex system and this is one instance where the measurements are FAR less meaningful to what will actually be heard. Compared to pretty much any other amplifier we have put up against the GaN 1, the difference is NOT subtle.