wjm@whuxj.UUCP (MITCHELL) (01/13/84)
I'm interested to hear about Suk Lee's problems with the NX 40 and dbx in general. For those of you who have had noise problems with the NX 40, I'd recommend the 224 which is about 50% more expensive, but QUIET (mine has negligible hiss and no audible hum). As for the comments about dbx pumping frankly I think dbx is getting a bad rap there. I've experienced no pumping with either piano music or HARP music, which is probably worse from a transient point of view. Most other users of dbx have not experienced these effects either, from what I've heard here on net.audio or in the hi-fi mags. Sure, Dolby C won't have this alleged problem, but it will introduce problems of its own, if the frequency response of the tape deck is slightly inaccurate, C will exacerbate the problem. I've heard that a 1.5 dB error, will translate into a 4+ dB error through the Dolby C process. Also, keep in mind that dbx gives you 50 dB of noise reduction, while Dolby C only gives you 20 dB. Don't get me wrong, I'm not saying Dolby C is bad, just that dbx is better and that Mr. Lee is giving it a bad rap. (Naturally, these are my personal opinions and not those of my employer, the Central Services Organization.) Bill Mitchell CSO Whippany, NJ (whuxj!wjm)
cbf@allegra.UUCP (Francois) (01/13/84)
Just to lend Mr. Lee a bit of support, I'll testify that I don't doubt his word in the slightest as to his finding pumping and breathing problems with his dbx unit. As far as I'm concerned, he's not giving dbx a gratuitous bad rap. I honestly can't say anything about dbx-encoded discs, but I'll repeat what I said earlier about the Teac V2RX tape deck ($520 list) that I owned for all of six days before I returned it. To wit, although I had ABSOLUTELY NO idea about dbx's alleged problems before I bought it and therefore NO preconceptions, I immediately detected my deck's shortcomings in dubbing some of my (mass-produced, of course -- can't hear Gilels otherwise) piano recordings. I'd describe what I heard as a sort of ripple effect, that is a detectable, though not excessive, burst of hiss accompanying loud passages. Of course, when the passage happens to be a single staccato note, the result is terribly distracting (once you detect the problem, you simply can't stop listening for it). Also the quieter the record itself (e.g. digital LPs), the more noticeable the problem becomes. There is a small possibility that the dbx circuitry in my deck was misadjusted, but I would tend to discount it, especially since the deck itself behaved superbly and was built like the proverbial battleship. Also when I took it back for a refund (Bryce audio in NYC was very nice about it), the employee who took it back and asked for a description of the problems muttered softly, "Yeah, that's the problem with dbx". It could be that with more expensive outboard units, the problem effectively goes away, but I'm not very eager to take that risk, especially when Dolby C is quite adequate for my home taping needs. Ever since then, I've started reading the audio mags (especially Stereo Review; Audio can be lukewarm and even down right cold toward a tested unit) with a huge grain of salt. -- "Yes, but is it art?" Charles B. Francois (decvax!allegra!cbf)
fish@ihu1g.UUCP (Bob Fishell) (01/14/84)
I can't speak for the NX-40, but I shall once again write in praise of the
dbx model 224 nr system. I have been using it for about 3 1/2 years now, on
a wide selection of music including solo piano works. I have discovered no
pump-wheeze noise problems, no residual hiss (what there is is below the
noise floor of my amplifier), in short, no audible trouble AT ALL, on any
type of recorded material. Of course, I use it with an open reel deck,
not with cassettes. Maybe that's part of the difference; open-reel tape
is much quieter than cassettes when no noise reduction is used.
I must reiterate: dbx provides calibration instructions with their units which
must be followed carefully. I think some of the problems folks are having out
there are related to improper calibration.
dbx works by applying 2:1 (dB) compression to the input signal, along with
preemphasis of the high frequencies. One thing this does is tax the high
frequency response characteristics of the recorder and the tape used.
Again, open reel decks are far better than cassettes in this category.
The best specs I have ever seen on a cassette deck ran into something like
19kHz on the high end. Open reel decks recording at 7 1/2 ips typically
go up to 24kHz. This response difference could also be a source of
problems for dbx users with cassette decks. Unless one of the better
decks is used, with metal tape, some of the information in the original
input signal could get squeezed out by the compression and preemphasis.
The result on playback would be distortion and a loss of high frequency
harmonics. This would be especially noticable on piano music, where
harmonic content and purity are the key to good reproduction.
I have found Dolby C and metal tape (I have the Harmon-Kardon CD201 deck)
to be perfectly adequate for many types of recording, but I can notice a
difference in the clarity and definition of the sound. I always know I'm
listening to a tape with the cassette deck, but the dbx-encoded reels sound
considerably more like the originals they're made from.
Cassettes are compact and convenient, but I don't believe that they will ever
match the quality one can get with open reels. Furthermore, I think that
dbx is probably best suited for open reel applications; cassette deck owners
should be content with Dolby. It's not perfect, but it's pretty good, and
it's economical.
Bob Fishellspoo@utcsrgv.UUCP (Suk Lee) (01/15/84)
Um, yes, perhaps. I don't want to get
into the debate as to whether Dolby C
or DBX is better: each has advantages
and disadvantages. All I'll say was
that I found the noise pumping quite
unbearable (the record was Windham
Hills WH-91025: George Winston,
"December"). Granted, dbx has
*TREMENDOUS* dynamic range, but in the
presence of narrowband high-level
signals, the companding action allows
tape hiss to start intruding.
It sounded like a "swish" accompanying
each stacatto note, obscuring the
higher harmonics of the piano.
The best solution is to try it yourself:
what I find to be extremely unpleasant
may not be so for you.
On the dbx 224: if I do decide to go
back to dbx, I'll gladly pay the
extra price to avoid the hiss/hum of
the NX-40.
From the pooped paws of:
Suk Lee
..!{decvax,linus,allegra,inhp4}!utcsrgv!spoocaf@cdi.UUCP (caf) (01/15/84)
Some years ago, when I first got a DBX disc decoder, I made some experiments in dubbing the DBX discs to cassette tape undecoded, and then playing the tape back through the decoder. I found that the music sruvived dubbing onto chrome tapes without objectionable side effects. Other types of cassettes generated annoying swishing. Recently, I tried using DBX encoding (I now have a 128 unit) with a JVC Stereo VHS VCR. Again, the result with standard tapes was terrible, much better with chrome. The best results so far have been with PD Magnetics T-160, whose thinner tape seems to give better head contact than a T-120. Unfortunately, the sound quality of available simulcasts in the Portland Oregon area is so wretched that there is little advantage to be derived from going theough all the fuss. In particular, the music (Opera and concerts) is so severely compressed that repeated listening is painful. But the process did work well when dubbing from records to the VCR. The only use I have found for that, however, is to overdub the network announcers' drivel that accompanies pictures of space shots. From the corroded ears of Chuck Forsberg. -- Chuck Forsberg WA7KGX CDI Portland OR (503)-646-1599 cdi!caf