Leaving your hifi powered on

[hoopsontoast]

All very interesting. Has anyone's ears been completely offended by the sound coming their 'cold' hi fi equipment?

Yup when I bought my new amp into the house from being in a cold car all day. Sounded miles better after it had warmed up to room temperature. :?

 

[Covenanter]

That doesn't really make sense! Transistor based devices will run hotter than room temperature because they are heat sources but the amount of heat they dissipate is pretty small (unless you have a Class A amp

) so they won't generally speaking get very hot. I think the main reasons for harmonic distortion in all circuits, transistor or otherwise, are (a) poor design and (b) poor components. If you keep your equiment well ventilated I doubt there is much temperature effect.

Chris

well, if you could get hold on open loop THD measurements you'd see that class A measures better than AB. class AB measures well on THD mainly due to excessive use of negative feedback. in class A power stages drain maximum amount of current at all time and excess is dissipated as heat but in this state transistors operate in more stable (thermally) environment. hence lower harmonic distortion. that's how I understand it works like. that's how I can now explain in my own words what I red somewhere else.

Nope! Class A has inherently less distortion because there is no "cross over" which you get in Class B.

Chris

 

[iceman16]

My amp does'nt sound bad from cold but a lot better after about 30 to 45 mins warmed up

 

[oldric_naubhoff]

Nope! Class A has inherently less distortion because there is no "cross over" which you get in Class B.

Chris

that too but also:

"There are advantages to class-A output-stage operation. As both transistors are conducting current throughout the entire signal cycle, there's no crossover distortion, which means less need for negative feedback. Both the current gain and the cut-in voltage of a transistor are dependent, in a nonlinear manner, on the transistor's junction temperature; if that fluctuates, then the current amplification of the transistor will be modulated by the change in temperature. With class-A operation, the transistors are handling the same average current at all power levels. Those transistors are therefore in thermal equilibrium and are not being operated anywhere near the cut-in voltage. With class-A operation, the power supply is under constant stress, whether or not the signal is present. As long as the maximum signal-voltage swing remains below the troughs of the rectifier ripple, the power supply is effectively regulated."

look, I'm not making this up.

 

[eggontoast]

Nope! Class A has inherently less distortion because there is no "cross over" which you get in Class B.

Chris

that too but also:

"There are advantages to class-A output-stage operation. As both transistors are conducting current throughout the entire signal cycle, there's no crossover distortion, which means less need for negative feedback. Both the current gain and the cut-in voltage of a transistor are dependent, in a nonlinear manner, on the transistor's junction temperature; if that fluctuates, then the current amplification of the transistor will be modulated by the change in temperature. With class-A operation, the transistors are handling the same average current at all power levels. Those transistors are therefore in thermal equilibrium and are not being operated anywhere near the cut-in voltage. With class-A operation, the power supply is under constant stress, whether or not the signal is present. As long as the maximum signal-voltage swing remains below the troughs of the rectifier ripple, the power supply is effectively regulated."

look, I'm not making this up.

That's all very interesting but it still only takes about 20 mins for a class A amplifier to stabilise. Besides getting back to the OP's point, only a complete fool would leave a class A amplifier on 24/7.

 

[Covenanter]

Nope! Class A has inherently less distortion because there is no "cross over" which you get in Class B.

Chris

that too but also:

"There are advantages to class-A output-stage operation. As both transistors are conducting current throughout the entire signal cycle, there's no crossover distortion, which means less need for negative feedback. Both the current gain and the cut-in voltage of a transistor are dependent, in a nonlinear manner, on the transistor's junction temperature; if that fluctuates, then the current amplification of the transistor will be modulated by the change in temperature. With class-A operation, the transistors are handling the same average current at all power levels. Those transistors are therefore in thermal equilibrium and are not being operated anywhere near the cut-in voltage. With class-A operation, the power supply is under constant stress, whether or not the signal is present. As long as the maximum signal-voltage swing remains below the troughs of the rectifier ripple, the power supply is effectively regulated."

look, I'm not making this up.

I'm sure you're not making it up! I've never studied the variance of transistor performance with temperature BUT I find it hard to believe that there is a significant effect at day to day temperatures.

Chris

 

[hammill]

My personal experience for what it is worth:

I always turn of my hifi & TV when I am not using it (even for twenty minutes). My Arcam Delta was my main amp for over 15 years and still gets used a few times a week in my gym system. It has been completely reliable. My first Hitachi TV was 13 years old and still working when I passed it on. My second Hitachi TV was 7 years old and still working when I passed it on. My Onkyo 875 is a few years old and no problems so far. The only hifi component that has broken on me was a pioneer CD player and it was a few years old.

I will admit that I think my system sounds better after it has warmed up but I do not know if it is:

a. The hifi

b. My ears

c. Placebo effect based on years of reading hifi mags.