Xref: utzoo rec.music.makers:9556 rec.music.synth:14879 comp.music:1656 Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!crdgw1!ge-dab!tarpit!bilver!alex From: alex@bilver.UUCP (Alex Matulich) Newsgroups: rec.music.makers,rec.music.synth,comp.music Subject: Re: dbx vs. Dolby C Noise Reduction Message-ID: <827@bilver.UUCP> Date: 22 Jul 90 19:47:25 GMT References: Reply-To: alex@bilver.UUCP (Alex Matulich) Organization: W. J. Vermillion, Winter Park, FL Lines: 30 In article apolivka@x102a.harris-atd.com (polivka al 60047) writes: > dbx > --- >1. I understand that dbx is basically a compander. > - Is the signal simply passed through a non-linear device such as a log > amp, or is there a dynamic gain device such as an AGC (automatic > gain control), or what? > - If it uses a dynamic gain device, then: > - How does the playback expander know when and by how much to expand? > - Is there a separate control signal recorded that is used to > dynamically adjust playback level? A compander basically consists of a variable-gain amplifier and a level detector. The playback expander knows when and how much to expand by comparing the signal to a refernece level, usually the -5 dB VU level. The voltage-controlled amplifiers (there are often two in both the compress and expand circuits are also frequency-weighted, along with the level sensors for each circuit. There is no separate control signal recorded that is used to dynamically adjust the playback level. Mine has a calibration control where you record a -5 dB 1 KHz tone on a tape, play it back, tweak a trimmer pot, and repeat until the playback level is -5 dB. -- /// Alex Matulich /// Unicorn Research Corp, 4621 N Landmark Dr, Orlando, FL 32817 \\\/// alex@bilver.UUCP ...uunet!tarpit!bilver!alex \XX/ From BitNet try: IN%"bilver!alex@uunet.uu.net"