Cold Start-Up Noises

[chewychevy]

Upon cold start-up my Mainline makes a slight humming noise raising in volume and then fading away for a total 3-4 secs of hum. It is then accompanied by white noise static for a second or two which also fades. 

When I hot start (turn it back on while tubes are still warm/hot) the there is an audible thunk in the speaker that accompanies the switch. My guess is that since the volume is not 0 that's the cause of the thunk and that the hum is the tubes starting the electron flow. Not sure what the white noise is.

Headphones still sound good in them. Just wondering if this start-up noise is regular, and if not what is the cause?

[Paul Birkeland]

Yes, there is startup noise in the Mainline.  This is a function of the 6C45 tubes themselves and the noises they make while warming up.

If you flip the amp off, then turn it back on somewhat quickly, you circumvent the warmup process and get a bit of a thud as the coupling caps recharge somewhat quickly. (The volume control position won't have any influence on this)

None of this is anything to be concerned about, it's all normal warmup behavior. 

[chewychevy]

Awesome. Thank You!