Quiet cooling fans for audiogear

a Variac can be used to reduce AC input voltage & slow down most muffin fans to acceptable low-noise levels.
Be sure to draw heat away from the component - don't blow cold air onto it.

Bob Bundas, What is the difference between blowing cold air onto the equipment and the cold air being drawn onto it by the harm air being drawn away? Any air being drawn away (heat as you say), has to be replaced by other air, which should be cold!

Salut, Bob P.

Bob the reasoning is so as to not introduce thermal stress points due to larger temperature differentials across a small heat-sinked area. Cold air blowing directly onto component causes a much larger thermal stress differential over a smaller area, with corresponding variations in semiconductor operating temperature, vs. drawing the colder air across a larger thermal area via drawing heat away from the heat sinked area.
Similar issues are noted when using glassware; thermal stresses occur across an even smaller glass area of a tube envelope vs. drawing the heat away.

Bob Bundus, so what you are saying is that LESS cold air is is introduced by induction than by forced draft? Remember that the harm air has to be replaced by something (i.e. cold air) for the cooling of the compenents to occur. The more warm air that you remove the more cold air moves in to replace it. Frankly I don't think that it makes any difference, unless the air is really cold and then either method will be bad.

Salut, Bob P.

no - the cooler air is simply spread out over a larger area