Xref: utzoo rec.music.makers:9495 rec.music.synth:14749 comp.music:1627 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!purdue!haven!decuac!grebyn!vrdxhq!bill From: bill@vrdxhq.verdix.com (William Spencer) Newsgroups: rec.music.makers,rec.music.synth,comp.music Subject: Re: dbx vs. Dolby C Noise Reduction Message-ID: <35879@vrdxhq.verdix.com> Date: 19 Jul 90 21:50:31 GMT References: Followup-To: rec.music.makers Organization: Verdix Corporation, Chantilly, VA Lines: 51 in article , apolivka@x102a.harris-atd.com (polivka al 60047) says: > Can anyone answer some or all of the following questions about Dolby C > and dbx Noise Reduction systems? > 1. I understand that dbx is basically a compander. > - Is the signal simply passed through a non-linear device such as a log > amp, This would cause distortion, as would anything acting instantaneously on the signal. Therefore the signal is averaged -- NOT an instantaneous process -- to control gain. > - Is there a separate control signal recorded that is used to > dynamically adjust playback level? No, just audio. A seperate signal might be a good idea though. > Dolby C Dolbys are compandings like dbx but to the highs only (different versions) except for the HX pro circuit which plays tricks on the bias. [...] > 3. The Nov '88 issue of Keyboard magazine, p147, mentions a problem > with dbx having a "tendency to cut off leading edges of transient > sounds, such as drum attacks and so forth." > What causes this problem and how serious is it? This is caused by the non instantaneous action descibed above. in article <56@maxx.UUCP>, tyager@maxx.UUCP (Tom Yager) says: > I trust my ears, and I like dbx better. This is a "love or hate" question, > and people on both sides tend to have pretty strong opinions. I trust my ears and I like niether best, usually. With no noise reduction the sound is just so much open and natural. Many peaple record with NR and play back without. This is NOT noise reduction, this is using the Dolby as a compressor or HF "enhancer". This is an example of not liking Dolby but not being willing to admit it. Depends on the music, sometimes you can't get by without NR. > To me, Dolby C seems to trample on highs, and makes quiet passages in the > music almost inaudible. For music that remains at a fairly constant volume, > its noise-reduction is obvious, and can be impressive. But if the level is constant, who needs NR? NOTE: I've noticed that on Portastudios the recording level is lower than conventional stereo recorders (Tone is O.K. therefore azimuth is O.K.). Therefore dbx may be considered a must. Has anyone else found the levels to be different? bill S.