Don Cox: > I had doubts about my mental arithmetic as I typed that - > but isn't a 3dB reduction a halving of signal strength? dB for voltage ratios is: 20 log10 V1/V2 3 dB = 1.414 6 dB = 2 10 dB = 3.33 20 dB = 10 40 dB = 20dB X 20dB = 10 X 10 100 26 dB = 20dB X 6 dB = 10 X 2 = 20 http://en.wikipedia.org/wiki/Decibel For power ratios: 10 log10 V1/V2 The math fo r replaying a mono disk and summing to mono instead of replaying in stereo: L&R channel outputs a unit of 1 Summing 1+1 = 2 = 6 dB in voltage gain for in phase signals. The noise, clicks, hiss, crackles, rumble appearing in a horizontal direction are random with no phase correllation thus sums to 1.414 in voltage level thus increases 3 dB. Thus we see a net gain + of 6 dB for the wanted correllated in phase audio signal but the uncorrelated noises only sums to + 3 dB. So a net gain of + 3dB for the wanted audio signal in respect to the unwanted signal. Those that dreams about using L or R only listening intently for the lowest noise and distortion can keep on dreaming while I just sum to mono as this ALWAYS produces the best result. Also distortion caused by the pinch effect, rumble, disk warp producing massive LF signals etc and other vertical only "distortions" are removed completely ONLY IF SUMMED TO MONO. One can hear this very clearly if matrixing to M/S and only listen to the difference,S, vertical component that only has all the noises and rumble with zero music content while the, M, correlated signal contains ONLY the best of the wanted content sans all of the dirt that can be removed by playing a mono disk. -- Best regards, Goran Finnberg The Mastering Room AB Goteborg Sweden E-mail: [log in to unmask] Learn from the mistakes of others, you can never live long enough to make them all yourself. - John Luther