today's preamplifier is not amplifying signal anymore because most source signal are high enough or even over to drive a power amp, all it can do is select and reduce the in coming signals, in this point the most important parts of the amp is the selector switch and volume control, they can effect the sound quality especially the quality of the volume control can represent the grade level of the pre amp, carbon film type is the most common one like Alps and nobel from Japan , they are middle class , the amp using them is not the real Hi End one, but one brand name P&G volume control , price very expensive in this type, I have not try it so I can't say anything to this stuff, the other type volume control is a 21 or 32 steps switch with resistors or transformer to control the voltage, only the real Hi End amp will use this type control but still count on the quality of the switch such as well known ELMA from SWISS , SHALLCO from USA they all really good but expensive, the quality count on contact's material, area, pressure, surface condition, etc, in this way I found out mercury switch will fit for those conditions, because of wet contact no pressure require , area is big no dust and oxide, and I was lucky can get 50 pcs from surplus guy for $1.5/pcs and turning hard wear too, but only good for 9 sets in volume 3 sets in selector, so I can only control from 10 o'clock to 2 o'clock , this pre amp with me almost 8 years and I still very happy with it, so I would to share this idea to everyone but brand new mercury switch will cost $20 each , one more thing volume control is not only control the sound level, it should when turn up , the sound stage come close to you and turn down it will go far from you, if you don't have that effect that mean your system need improve
tony ma
tony ma
