rs173@hou2e.UUCP (R.SILVER) (03/07/85)
a
after seeing 2 interesting articles i audio mag.(2/85), i am interested
in hearing how effective DNR is in reducing the noise on some of my very
old (irreplaceable-family,events,etc.) tapes.
does anyone sell these units commercially where i can listen to one,
(in the Philadelphia/New York City/Central NJ. areas) before going to the
effort of building my own, or the expence of buying one mail-order?
has anyone one the net heard a DNR unit operate? i would be very
interested in opinions !
thanx for any help !
Ron Silver .....hou2e!rs173fish@ihlpg.UUCP (Bob Fishell) (03/07/85)
> > has anyone one the net heard a DNR unit operate? i would be very > interested in opinions ! > *** AC T YOUR AGE *** Don't expect miracles from DNR. The system will make a difference when listening to inherently noisy sources like old 78's, AM radio, or non-hi-fi video tapes played through a stereo system, but you can't get something for nothing. I have a DNR unit connected between my VCR and my stereo. While it does cut down on a good deal of hiss, it also cuts into the already limited bandwidth of the VCR's audio playback capability. The amount of noise reduction is pot-adjustable, but the more noise you cut out, the more of your highs you lose. However, the effect is much better than what you get by using a simple lowpass filter (like your tone controls or an equalizer), which takes out everything. At least with DNR, high-frequency sound recorded at relatively high levels still gets through. Unfortunately, any treble information recorded near or below the noise level is lost, although your ear can normally distinguish it from the surrounding noise (the cocktail party effect). Nonetheless, a DNR unit is worth having if you have cause to listen to noisy sources. If you really want to get exotic, though, you can get a 3bx or 4bx audio expander from dbx. Such a unit can really clean up sound, doing a much better job than DNR. Unfortunately, it will also clean out your wallet. I have a much simpler (and cheaper!) 1bx dbx expander which, when used in conjunction with my DNR unit, provides a fair amount of noise reduction without hurting the bandwidth any more than what can be attributed to the DNR unit alone. While it makes watching TV and listening to some of my old, abused, and irreplacable records much more enjoyable, it's not the same as listening to a high-quality recording. You can't make a silk purse out of a sow's ear. /_\_ Bob Fishell ihnp4!ihlpg!fish
sdyer@bbnccv.UUCP (Steve Dyer) (03/08/85)
I have a Burwen Dynamic Noise Filter which uses, I believe, discrete
devices, unlike National Semiconductor's DNR chip which operates on
the same principles. I have found that it works very well on many
recordings, although REALLY noisy source material can cause audible
pumping.
Radio Shack is selling a "Video Sound Processor" which incorporates
National's DNR chip (along with a lot of extra gunk like stereo
synthesis). It might be a cheap (< $100) way to get DNR in your system.
The Burwen unit is apparently still being manufactured and sold by
Infinity (which bought out KLH (which bought out Burwen)). It lists
for $350 which is a bit steep for non-critical noise-reduction.
--
/Steve Dyer
{decvax,linus,ima,ihnp4}!bbncca!sdyer
sdyer@bbnccv.ARPAmat@hou4b.UUCP (Mark Terribile) (03/10/85)
>> >> has anyone one the net heard a DNR unit operate? i would be very >> interested in opinions ! >> >Don't expect miracles from DNR. The system will make a difference >when listening to inherently noisy sources like old 78's, AM radio, ... >The amount of noise reduction is pot-adjustable, but the more noise >you cut out, the more of your highs you lose. However, the effect >is much better than what you get by using a simple lowpass filter > ... Unfortunately, any treble information recorded near or below the noise >level is lost, although your ear can normally distinguish it from the >surrounding noise (the cocktail party effect). > Bob Fishell Well, Carver claims that the autocorrelator on his top-of-the-line preamp uses a bank of comb filters, designed so that a significant signal in the midrange or lower treble will open the gates on all of the areas where harmonics are likely to appear. I believe it's true, since I once (and only once) heard mine fooled by an old piano recording (Schnabel, if that matters) which had a passage of notes in rather chromatic clusters ranging up and down the second and third octaves from the top of the keyboard. You could hear the noise following the music and (apparently) its harmonics up and down the scale. I don't believe that Carver sells the autocorrelator seperately (and if he did, it would cost a bundle) but a less sophisticated unit that he designed was sold some years back by Phase Linear (Carver's first venture). I don't know how it compares to the one I've got -- it is supposed to be a little more noticeable in operation -- or whether it's still available. Might be something to look at, though. Also, the Feb AUDIO magazine had an article about a DNR box available in kits of various sophistication, from just the semiconductors (about $35) to a complete kit with a silk-screened cabinet for about $120. -- from Mole End Mark Terribile (scrape .. dig ) hou4b!mat ,.. .,, ,,, ..,***_*.