You need to have high quality low noise tubes. I changed out all of the OEM tubes in my WOO headphone amp for just those reasons. Hiss and buzz. Perhaps someone with your headphone amp can make a recommendation. Headphones are very revealing and a lot of tubes which will work well elsewhere just won't work. Good luck.
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Tubes are inherently more noisy than semiconductor/ transistor amps, but some feel the benefits of the warm, natural sound quality outweigh those negatives. The Sennheiser HD800 headphones are very revealing so you would hear all of the nasties that tubes can produce.
..."is it true that in order to have tubes in the system, there are forms of hum, buzz, snap, crackle and pop during quiet passages? "
No. That is complete BS. And there is no need at all to use selected low noise tubes in a well designed circuit, except possibly there may be some transient benefits in a tube phono stage. But you don't want or need a phono stage. It is amazing to me how these superstitions about tubes persist among audiophiles. If a tube goes bad, yes, you can have some of those symptoms (mostly "pops"; hum and buzz are usually due to grounding or power supply problems, not gain devices). If you have "pops" or other symptoms of tube aging, you buy a new tube and fix the problem yourself. If a transistor goes bad, most typically you have no sound at all and are at the mercy of someone else to fix it who may or may not know what he/she is doing.
Transistors, particularly bipolar, can produce pops and ticks as well. This is called "popcorn noise" and is a form of low frequency thermal noise.
The transistor may function normally otherwise.
Replacement of transistors with leads is not difficult if you have desoldering equipment (not always needed but useful) and you have a suitable replacement. If the transistor is a surface mount chip device, forget it. These require special (and expensive) desoldering tweezers that most folks (or even repair shops) will not have the inclination to buy.
If the popcorn noise is coming from an IC opamp, then you just replace the whole IC. Most are even cheaper than discrete transistors these days.
Re ICs. Sure. The average Joe hobbyist would not have much chance of replacing a typical IC without destroying the PC board and possibly the replacement IC in the process. This is even assuming that Joe can identify which IC needs replacing. (I am that "Joe", too, so no diss is intended.) And then there is the fact that if your unit is more than a few years old, that IC may have become unobtainium. Actually, I don't think we disagree; it seems you are acknowledging that tubes are less prone to sudden failures and that tube gear is easier for the hobbyist to diagnose and repair. At least that's what I think.