Stock First Watt F4: Complete Distortion Measurements?

[ajant]

I count myself very lucky to have this amp. But AFAIK, the stock First Watt F4 never got put through the wringer the way the J2 did. https://www.stereophile.com/content/first-watt-j2-power-amplifier-measurements

And unlike the J2, no distortion measurements were included in the F4’s manual. Here's some ("quick and dirty?") distortion measurements from 6L6's first build of the F4 build, post #2.
https://www.diyaudio.com/community/threads/a-guide-to-building-the-pass-f4-amplifier.234355/

Okay, so even a stock F4, like I have is probably not a low distortion amp. But my speakers are ~ 94db/w, they don't fall much if at all below 7 ohms and only play down to 70Hz, below which my Rythmik F12 subs takeover.

So, with a line stage like the Aikido Rev. F providing plenty of gain
https://glass-ware.stores.turbify.net/ainost.html
https://tubecad.com/2018/03/blog0415.htm, how much 3rd or 2nd harmonic distortion would the F4 produce which would likely be audibly offensive?

 

[cpcat]

Have you seen the 6moons review? It has some distortion measurements.

6moons audio reviews: FirstWatt F4

Seems like a fine match to me- how does it sound?

 

[ajant]

Well, what happened was that Grovergardner here drove me to pursue the SP14 version of the Aikido. https://www.diyaudio.com/community/...or-less-than-great-sounding-cds.408331/page-4 I found that here.
http://www.tubes4hifi.com/pre12.htm#SP14

But after learning earlier that Don Sachs was working with Lynn Olson to co-design Lynn's new no-compromise 300B p-p amp-and then after reading Don's praises for Roy Mottram's SP14, I then when to check out Don's version.

custom line stage

Emailing Don about optional upgrades, I was told that the Sachs # 2 preamp
was now discontinued. I was about to search for a used one when I found a link at Don's website to his new preamp. https://www.spatialaudiolab.com/revelation-preamp

While I was less thrilled with its range of output connectivity and overall aesthetics, everything about its circuit design and parts quality and price makes choosing it pretty much of a no-brainer to drive the F4.