..and for those of you still with us, here's a little respite from the technical:
4 brief Reviews of the 388 brought to you by the good people from eCoustics:
(you'll have to do your own fact checking...
Here's a link to a 10 minute utube vid testing out a 388
All About Dbx Noise Reduction
"It seems hard to believe now, but at one time the type of noise reduction process you used was as vital to the success of an analogue multitrack recording as the size of your hard drive is today! Professionals enjoyed the relative merits of noise reduction systems such as Dolby A (or the much improved Dolby SR later) or Telcom C4, while the home studio tended to use equipment fitted with Dolby B or Dolby C (and a few late models with Dolby S), or with one of the Dbx formats (Type I
or Type II).
The basic idea of all these systems was to reduce the dynamic range of the input signal in some way prior to recording to tape. On replay the inverse process was used to restore the original dynamics (more or less) while also reducing the apparent tape noise into the bargain. The success of such systems was variable, though, and the best (Dolby A initially, and subsequently the remarkable Dolby SR) are technically complex and tackle the audio in several independent frequency bands to maximise control and minimise modulation side-effects.
The Dbx noise reduction system was relatively simple in comparison and, although not so widely used in professional circles, was adopted readily in the semi-pro markets. These Dbx systems, developed by David Blackner in the early 1970s, essentially employ a wide range 2:1 compressor on the record side, with a complementary 2:1 expander on replay. Since the 2:1 ratio is used over the entire dynamic range of the input material, there is no critical threshold requirement, and so no need to accurately match record or replay levels when tapes are moved between machines. This has always been one of the drawbacks of the Dolby systems, and this is the reason why Dolby tone is recorded at the start of multitrack tapes in professional studios.
In any broadband noise-reduction system such as Dbx, dynamic changes caused by a low-frequency source ? a bass solo, say ? will result in the level of tape noise being modulated, and with no high frequencies in the recorded signal to mask it, high frequency tape noise will become very obvious. To overcome this significant side effect, the Dbx system applied pre-emphasis (high-frequency boost) on the record side and a corresponding de-emphasis on replay. The idea was to reduce the audibility of high-frequency noise generally, and so the pumping artefacts of the companding process were less audible.
On a good day, with everything set up perfectly, the Type I
system was capable of providing as much as 30dB of noise reduction ? far more than Dolby A ? although it was prone to audible side effects. The difference between the Type I and Type II formats comes down to the details of the level sensing circuits used to control the compression and expansion processes. Type I
was optimised for high-quality, wide-bandwidth open-reel recorders, whereas Type II was designed for the rather less reliable results obtained from cassette recorders. Consequently, Type II noise reduction was not as powerful, and more prone to mistracking side-effects.
Whereas the Dolby systems only compressed low-level signals which were in danger of being lost in the tape noise, the Dbx system compressed everything regardless of level and, although far simpler and cheaper to make, this was also the system's primary weakness. If the recording medium was entirely linear at all levels, a 2:1 expander would always undo the dynamic changes applied by a 2:1 compressor, so the replayed signal would be identical to the recorded signal (ignoring the problems of compressor overshoot and the like). However, as we all know, recording tape is anything but linear, especially at higher levels where tape saturation occurs. The saturation effect means that a high-level input signal is replayed at a lower level and with a different frequency response (and more distortion). Since the expander can only work with the signals found on the tape, the original (but saturated) high-level signal ends up being decoded incorrectly. This is known as a 'tracking error' since the dynamic reconstruction of the expander fails to track that applied originally by the compressor. Tracking errors can also be caused by drop-outs, an azimuth error, or if the machine is not equalised correctly for the tape being used, and typically result in a dull and dynamically compressed (or 'choked') sound.
So, whereas the usual advice is to drive analogue tape fairly hard (even when using Dolby noise-reduction systems) to obtain the best noise performance and the often desirable characteristics of tape saturation, try this with a Dbx system and you will be badly disappointed! For this reason, many recorders that use Dbx have switches to disable the noise reduction on some or all channels, so that good old-fashioned tape saturation can still be used creatively if required. It is also a good idea to switch the Dbx off if recording transient-rich instruments such as percussion, since the companding may mistrack on fast transients.
When Dbx noise reduction is being used, it is generally wise to err on the side of caution when setting levels. Keeping peaks below the point of saturation gives the expander the best chance of reconstructing the original signal properly. This usually means 0VU is the absolute maximum level, rather than the average value to aim for, and recording at a slightly lower level than you would without Dbx isn't really a problem as the amount of noise reduction is so great anyway. It is also vital to keep the tape heads clean and demagnetised, and to have the machine serviced regularly and aligned correctly for the type of tape you are using, to ensure that what goes in comes out properly." Hugh Robjohns - SOS mag article excerpt.
TapeOppers weighing in on dbx with the 388
joel hamilton said:
I recorded a ton of stuff on one of those. I never used the NR. Just print bright and turn down the top if you are getting too much hiss.
I just learned to track bright as fuck with that machine, and then attenuate the high end a little, rather than throwing a wet wool blanket over everything by using the NR.
I always thought the NR on that machine was a joke, like a lowpass set to 5k, rather than a dynamic companding system like SR.
Make your own decisions, but I always hated the NR on those things. The amount of hiss I got was directly proportionate to how bright I printed the sounds in the first place.
I'm no expert. It's your machine, do with it whatever sounds best to you. If you like the way your 388 sounds with no DBX, leave it off. I've tried it that way, but I didn't like the hiss level on playback.
I've found that you can't slam the meters or record at or over 0 VU with narrow-format recorders like the 388 and MSR16 because the DBX will mistrack and over-accentuate the compression and expansion effect, compressing the sound more on playback and rounding off the top end. Leave 2-3db or so of headroom and the DBX can work on reducing the noise floor and doesn't overly "warm" the track so much. The DBX still affects the sound, just not as much as when hitting the track hard.
"The Ghost of FM
" Tascam Forums said:
The dbx noise reduction is a key element in the overall quality and performance of the Studio8.
It is basically responsible for the elimination of all tape hiss and much of the internally generated modulation noise. It also allows for far less adjacent channel crosstalk or bleed-through so that you can better isolate a singular track in the mix and not hear its neighboring track(s) playing in the background.
dbx also provides you with a flatter frequency response as it allows the recordings to be made at lower levels where response curves are much flatter and distortion levels much lower as well.
Keep in mind that the Studio8 is indeed a narrow track format machine and was designed for tape economy as one of its paradigm features. dbx is a true benefit feature for that machine and even of much benefit to the 388's bigger brothers that have wider track widths and faster tape speeds.
The only open reel machines I would suggest not needing dbx would be half track stereo decks which have hotter calibration setups and wider guard bands in-between the tracks to reduce bleed-through."
" Tascam Forums said:
I've been recording with the 388 for about a year, and lately without the dbx. What an amazing improvement! I SAY FORGET THE DBX!! without it you can push the levels quite hard and get some nice compression, and the playback is MUCH more realistic--clear and with no pumping or swelling or wet blanket effect. also, I think it's important to not let tape hiss become some sort of horrible bogeyman--it's OK to have a little hiss--IT'S TAPE, AND WE LOVE TAPE!! And the feeling of simply getting back what you put in is much more honest. try it. hit the tape hard you'll be happy.
" Tascam Forums said:
Tascam 388: Use DBX or not?
I agree that dbx isn't always needed. If you are recording material that doesn't have quiet passages near the noise floor, dbx isn't really necessary. If you've got some pauses or quiet (relatively) acoustic stuff going on, dbx can keep the hiss from being front and center.
You Leave 1000x, repetitive instrumental circa 1988
Example of 388 recording made with dbx "on" while tracking, "off" on mixdown.
( from an old cassette copy of the tune. Will have to bake that Ampex 456 reel one of these days...)
Link to preview of excerpt pages from "Tascam: 30 years of Recording Evolution"
with pics and historical writeups on the products and technology of the 1979-1990 era.