Why do Tube Amps sound more romantic v SS amps

"Tube amps in general are far more stable than that!” 

what is “”than that”, atmasphere?

Push-Pull amp tubes misbalance cause increase of odd harmonics, even 5% misbalance  is causing more that 0.1% dist. increase easily.

keeping tube amp in a good performance condition is very costly, period. if not, you’ve got a “romance” 

+1 "Tube Amps sound more romantic” “romance" cost a lot of money though :-)

I disagree on comparing all tube amps to all SS amps ! There are amazing sounding/performing/powerful SS amps! I saw some very good tube amp products, simple and genius as well! In general, SS amp aging stabilizes after about 100hr run time, while tube amp aging never..  

1) tube amp sound changes almost every 50hr due to tube emissions degradation, bias-balance degradation., accelerated resistor/capacitor aging, etc

2) most of good “coloration” (aka tube amp specific distortions) of tube amp caused by tube's type, tube aging condition, output transformer problems such as core-magnetics-linearity-inductance-mutual and actual-resistance-inter-coil capacitance, linearity in the of tubes’ used, and regular bias-balance adjustment. 

@atmasphere "an imbalance in power tubes will cause a 2nd harmonic, not a third"

not really, AB imbalance does contribute directly into third (odd) order harmonic increase. Perfectly balanced second (even) only order harmonics distortion, AB designs “distort" A and B the same way only if tubes are perfectly matched, which NEVER happened. it is very hard to pick matched tube replacement, which will age at the same pace to the <1% point.

Good designed SS amps have many AB transistors in parallel, which reduces imbalance problems. SS amps I have all are “maintenance free”, and there is no need to change any transistors due to aging degradation in 100 000 hrs life time.

@invalid "with simple designs fewer parts count” which leads to higher distortion, shorter “relatively good performance" lifespan, and higher maintenance cost, in order to bring tube amp back to spec. SS amps aging at much slower (x100) pace then tube, pl admit it.

"You may not get 100,000 hours on the equipment before corrosion has had a chance to damage the semiconductors"

-good point on corrosion! In my experience corrosion hits tube amp sooner than SS! Just look at the power transformer, capacitors, output transformer inside the 20yr old tube amp.

@atmasphere agree with you on tubes could match better than PMOS/NMOS or N/P BJTs. Please try to measure distortion of tube amp while adjusting bias/balance of the output tubes, and you’ll see how sensitive it is. Then please repeat the same after 50+ hrs. If you are luky, and your AB tubes are aging the same pace, then distortions will not increase much. There is a lso big issue with output transformers in the tube amp, depending on core magnetics, resistance of coils, symmetry etc you will get variety of imbalance/distortion/FR problems, which does not exist in SS>