Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 (Tek) 9/26/83; site vice.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!ihnp4!zehntel!tektronix!tekchips!vice!shauns From: shauns@vice.UUCP (Shaun Simpkins) Newsgroups: net.audio Subject: Re: Controlled compression, etc Message-ID: <50@vice.UUCP> Date: Wed, 17-Oct-84 12:25:32 EDT Article-I.D.: vice.50 Posted: Wed Oct 17 12:25:32 1984 Date-Received: Sun, 21-Oct-84 12:40:38 EDT References: <86@azure.UUCP> Organization: Tektronix, Beaverton OR Lines: 38 Controlled compression of CDs was proposed as a means of getting 20-bit effective dynamic range out of CDs without building a 20-bit digitizer, which is very difficult to build. I stated that CDs have a noise floor that is below the average listening room's but above hearing threshold. By increasing the dynamic range of the system we improve the reproduction of near-threshold level signals. IF the ear can discern 8 or 10 bit quantization at such low levels (which I don't think it can) compansion will shove the signal level up to a point where the resolution is higher. The use of a control track for gain riding eliminates the envelope tracking error of present compansion systems. I agree that preceeding a digital recorder with a dbx unit is pointless from a distortion point of view. I think the real issue in this conversation was not `is the CD inferior' which I think it isn't for home use, but `what should be the professional quality level', over which there is some reasonable concern. I am concerned over the blanket approval of digital techniques as a panacea to the problems of multi-track mixdowns. It isn't. Let's take an example - we have two 16bit digital words. The LSB of both fluctuates randomly (i.e., the noise floor of the digitizer is equal to 1 LSB). We now add them together. Oops! The 2nd LSB is dithering, too. The noise floor has moved up from 1/2 LSB average to 1 LSB average. Do this a few times and you've lost a lot of your resolution to noise. My point? If recordists are not to sacrifice their beloved multitrack techniques for minimalist recording methods (I doubt that they will) the recorders they use must be better than our players. This means more bits or a noise floor of the recording system before the sampler of much, much less than the digitizer's resolution. Compansion is a way of achieving this with present systems. The wandering squash, -- Shaun Simpkins uucp: {ucbvax,decvax,chico,pur-ee,cbosg,ihnss}!teklabs!tekcad!vice!shauns CSnet: shauns@tek ARPAnet:shauns.tek@rand-relay