[illkemist]

I'm just curious. I read all these reviews of products on this board and each one features updates based on burn-in hours. Has anyone noticed a product getting worse the longer they've had it?

 

[Uncle Erik]

Not with a headphone amp (yet) but I've seen a number of tube radios degrade over time.

Heat destroys components, so the longer something is on, the more likely the capacitors, filters and resistors drift out of spec and stay there. Usually, that muddies up the sound a little and makes them drift in station lock, as well. Amps are less complicated, but you can still hear problems in amplification sections once you've fixed the rest of the circuit.

Sometimes, it's fun to turn the set on (safely) between replacing each component. You can literally hear it shape up and start sounding good again, bit by bit.

To answer your question, yes, even the modern components will drift and change value depending on heat and age. Eventually, they fail. I haven't listened to a poly cap or a film resistor fail yet, but you can hear it in the wax/paper caps and carbon resistors.

 

[Bizzel]

Everything degrades over time. For moving parts such as drivers it's relatively quick compared to solid-state parts but they'll all eventually fail. Whether you hear them slowly breaking-down depends on your ears and how well you know the device.

 

[jamato8]

Yes, the older carbon resistors do drift. One method is to heat them in an oven, at a reasonable temp and then coat them. It is often the moisture that cause them to drift and change. You measure them again after this process. That was with the Allen Bradley but with the modern carbons like Riken Ohm or (can't remember the name) they don't drift and hold up for a very long time as well as sounding excellent.

Yeah, those old wax caps were something else. I actually have some from the 1920's that are still good and this after much use! But that is very, very uncommon.