Break in period for tube amp. How long?

Please define "awful". And what was your previous amp? Are you still using the same speakers...what are they?

Thank you everyone for your kind input.
I went from ARC VT100 MKIII to a used pair of NAGRA VPA's.
Well, I was so impressed with the improvement (dynamics,air, soundstage, placement ambience etc.) that I upgrade to the current new VPA model. With the new unbroken in model, however, the sound seems congested and harsh........i.e.awful. I'll try to break them in to 100 hrs as suggested. So far I have about 10 hrs break in time.

Fatparrot. I am using the same speakers B&W CM4 as I await my ordered PARSIFAL OVATION's. Thanks for your input.

C123666 how would unbroken in capacitors affect the sound?Thank you

Something about the capacitors "not reforming" is what several techs advised me of

C123666, yup, "congested and harsh" seems to indicate an entire amp [not just tubes, alone] that has not yet broken in. By 24 hours, you should notice an improvement...72 hours should get you 90% there, for the tubes! Some equipment, especially speakers, takes quite a while to fully break-in.

Use only one CD for break-in, preferably one that you know, and is of audiophile quality. That way, you can monitor fidelity changes, without confusing your ears. DO NOT USE A CRAPPY CD...THE SOUND MIGHT APPEAR TO GET WORSE!