Some components are affected by the warm up of the equipment
Take a simple transistor (and my paradise phono is full of them
)
Measure the HFE (current Gain)of it cold and then hot it will be different and this is measurable, weather that will have an effect on the sound depends on the implementation of that transistor in the circuit.
Bias current in Ma is another measurable value that changes during the warm up cycle and normally final adjustment of this is after warm up or alternatively on Naim power amps some recommend the setting of the bias is done cold in mv across the emitter resitors, which ever method you use there is a measurable difference between cold and warm.
The Paradise phono use a shunt regulated power supply which has an output of 18v, measure this cold and it outputs 18.8V these are all changes that go on in an amp during warm up which may only take mins ?
In a new amp full of stock components there is certainly a period of where some new components take time to settle down to there intended value particularly electrolytic capacitors and how quickly they form is dependant on the voltage and current applied across them in the circuit and how old they are from new.
In an old amp, old electrolytic’s, drifting carbon and aging cold soldered joints resistors can cause problems with an amps stability you can notice this more if it has been switched off for a long period and it sound crap when you switch it on but gets better after a period of time.
Just my 2p
Alan
PS our cat prefers the tivo box
