12AU7 Gain Question

The 2016 is clearly an error or "misprint". That’s more like a transconductance reading than mu (not possible to have mu that high). I wonder if the doofus seller mixed those readings up (don't do drugs).

Don’t use a multimeter. I’d just use them as is. Whether that mu is actually 16 (good!) or 20 (ok) it’s probably fine. 20 to 16 is still within 20%, which is close enough for most applications.

12AU7 has a mu (usually indicated by the Greek letter for “m”) of 16. If your tubes are all 12AU7s, then mu = 16. Mu is linearly related to gain, usually indicated as “A”. But mu is a product of transconductance (Gm) multiplied by plate resistance (Rp). These parameters vary somewhat according to plate voltage, grid bias, and plate current. 12AU7 has a Gm of about 6700 micromhos, when new. But if you measure Gm of several, they’ll vary a fair amount around that value. So all these numbers are “soft”, just a rough estimate. Your vendor may have sorted those tubes based on noise, but you can use any of them in any socket fit for a 12AU7.

Thank you very much guys, that is all very good information.