Heat in class A equipment


Heat is one of the biggest enemies of electronic equipment. Does anyone know if this Heat is only at the output transistors and their heatsinks o8is it also present in other components within the unit. 

 

I was planning to remove the top cover and with a IR thermometer going to check temps..

 

Has anyone done this? 

vanson1

 Unless the amp is designed badly, the heat in class A SS amps is usually confined to the output stage.  And almost all components will be fine except the electrolytic caps.   The challenge is to keep the caps as cool as possible.

 

As noted above, the primary source of heat in class A SS amps are the output transistors.  That's why they're mounted on the heat sinks.  However, if they are used properly and have adequate temperature control, they're probably not going to be the first things requiring maintenance.

Capacitors, in particular the ones in the power supply, will age the most rapidly.  While their eventual failure could prove catastrophic, long before then they will suffer from lost capacitance and increased ESR, which means less power available and more noise.  This is why Nelson Pass, whose primary interest is sound quality, gives different advice than a person that is just looking to get the most use for their initial outlay.

Volume level was mentioned somewhere in above post. With a class A amp, this has no bearing. The amp is running flat out in spite of the volume level, even at idle. 

 All electrolytics die in time. It is just a matter of when. Some have longer service life than others, and are rated thusly. 

 I would think that sound quality and service life could go together in a design, especially at the asking price of the component.

Class A amps are designed to run hot so as long as the unit is vented properly you have nothing to worry about: I had a Threshold Stasis Class A/AB circa 1988 that was biased to run Class A most of time so it got very hot and I never had an issue until I got tired of it & sold it in in 2010: The designers like Nelson Pass know this and his companies Threshold & Pass Labs have buiding hot running & long lasting amps for years.If you are worried about heat, you should not be considering Class A amps or you can leave it off when not in use and turn on 2 hours before use.