dbx Noise Reduction for R2R Machines

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LanceTF

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I hooked up a Tascam DX-4D noise reduction unit to a TEAC A3340S. After recording an acoustic guitar, drum machine, and electric bass guitar, it was quite 'breathy' sounding and the bass guitar (on track 1) was terrible with rumble and distortion. Is there an alternate dbx unit? and what was the noise reduction model sold with the A3340S at the time?

I am aware of the dbx 155 but it is hard to find. Any suggestions of making the best of the DX-4D would be appreciated.

Thanks,
Lance :confused:
 
Not sure what works with what machine but I do know if the NR unit is not calibrated right you will hear a lot of unwanted things. Sorry I can't help more.
 
Without the mod, the unit will not process properly, so you must do that in order to use it. Follow the link Blue Jinn posted.

Tascam DX-2D, DX-4D DBX Modifications

Also once done, you need to make sure your deck is calibrated properly and that you use recording levels that are not pinning the meters like you might do on a machine with no noise reduction.

Cheers! :)
 
LanceTF said:
I hooked up a Tascam DX-4D noise reduction unit to a TEAC A3340S. After recording an acoustic guitar, drum machine, and electric bass guitar, it was quite 'breathy' sounding and the bass guitar (on track 1) was terrible with rumble and distortion. Is there an alternate dbx unit? and what was the noise reduction model sold with the A3340S at the time?

I am aware of the dbx 155 but it is hard to find. Any suggestions of making the best of the DX-4D would be appreciated.

Thanks,
Lance :confused:
Click to expand...

Every dbx unit I've heard, onboard or outboard, exhibits some level of breathing. Later models used several bands of processing which made the breathing less annoying.

In general, I advise any & all users of analog recording equipment to avoid any dbx unit. Either use Dolby B, C, or S, or no NR at all. Later model machines, like a 34B, 38, etc., with premium tape (3M 226, Ampex/Quantegy 456, BASF/RMGI 911 or 900, ATR, etc.), can deliver pretty good s/n ratio w/o NR.

If the user still wants to reduce noise further, a Dolby B outboard unit can provide around 8 dB of NR, w/ very inaudible side effects. Dolby C provides a little more, around 15 dB, & Dolby S around 18 dB. But C & S type outboard units are rare & expensive. B type, however, is always available on the web for pretty cheap.

Again, some people really like dbx. I hate to diss any product, but dbx is one of a few vendors that never made a product I liked. In going for astronomical noise figures/specs, they got carried away & audible side effects were obnoxious. I always felt that dbx no. 1 priority was winning the specsmanship game. They put listening quality on the back burner in doing so.

I use a Tascam 3030, 2 track 15 ips unit w/o dbx, although it has onboard dbx type 1. The hiss is audible, but not excessive. But if I want dead silence between songs & during quiet spots, then NR can provide that. Dolby B is my 1st choice since it doesn't ruin the signal. I hope this does not start a war. BR.

Claude
 
Thanks for the info. I did some reading and found that the TEAC AN-300 was the noise reduction unit compatible with the A3340S unit. It is dolby.
I did prior recording without any NR and the 'hiss' wasn't too bad. I'm searching for the internet to buy the AN-300.
 
dbx vs Dolby isn't exactly mods vs rockers, but ...

I confused the 3340 with the 3440. The RX-9 goes with teh 3440 vice 3340. Either way the DX-4D won't work properly (shouldn't actually work at all) without the modification linked to above. This is easy and you don't even need to solder anything, I stuck a jumper made out of a small piece of stiff wire on the points that need to be jumpered. You'll find various opinions regarding dbx vs Dolby, dbx does cut out hiss substantially, and as indicated above, probably has the best overall NR "specs", but doesn't take kindly to overs. Dolby is more forgiving, but also requires more careful calibration. dbx Type II is more apparenlty more similar to Dolby B, and more forgiving, and is recommedned for 7.5 ips and lower speeds. (A two channel type II unit jsut went for $10 +ship on E*ay)

The AN-300 is a Dolby "B" unit, it will be fine, but it came with an alignment tape, so make sure you get that if you want to calibrate it properly. You will get more hiss reduction w/ dbx or with Dolby C, S, or SR, but these are going to be harder and/or more expensive to find.
 
Blue Jinn said:
dbx vs Dolby isn't exactly mods vs rockers, but ...

I confused the 3340 with the 3440. The RX-9 goes with teh 3440 vice 3340. Either way the DX-4D won't work properly (shouldn't actually work at all) without the modification linked to above. This is easy and you don't even need to solder anything, I stuck a jumper made out of a small piece of stiff wire on the points that need to be jumpered. You'll find various opinions regarding dbx vs Dolby, dbx does cut out hiss substantially, and as indicated above, probably has the best overall NR "specs", but doesn't take kindly to overs. Dolby is more forgiving, but also requires more careful calibration. dbx Type II is more apparenlty more similar to Dolby B, and more forgiving, and is recommedned for 7.5 ips and lower speeds. (A two channel type II unit jsut went for $10 +ship on E*ay)

The AN-300 is a Dolby "B" unit, it will be fine, but it came with an alignment tape, so make sure you get that if you want to calibrate it properly. You will get more hiss reduction w/ dbx or with Dolby C, S, or SR, but these are going to be harder and/or more expensive to find.
Click to expand...

Thanks for the update - I'll experiment with the DX-4D a bit more. In the meantime I'm using a TASCAM 246 cassette multitrack and was surprised by the decent quality of the cassette format. I keep the tracks to 4 with an external bounce to a 2 track reel to reel and do 2 or 3 superimpositions (Abbey Road term for overdub) once it's bounced back into the 246. Funny that my ProTools system is beginning to collect dust on the shelf. I'm having a blast. :)

Question: Does the DX-4D need to be calibrated as well? I did have the A3340 serviced about 2 months ago.
 
LanceTF said:
Thanks for the update - I'll experiment with the DX-4D a bit more. In the meantime I'm using a TASCAM 246 cassette multitrack and was surprised by the decent quality of the cassette format. I keep the tracks to 4 with an external bounce to a 2 track reel to reel and do 2 or 3 superimpositions (Abbey Road term for overdub) once it's bounced back into the 246. Funny that my ProTools system is beginning to collect dust on the shelf. I'm having a blast. :)

Question: Does the DX-4D need to be calibrated as well? I did have the A3340 serviced about 2 months ago.
Click to expand...

Cool. The mod is really easy to do to the DX-4D. Like I said in another post, it takes longer to unscrew the bottom than it does to make the mod. There are "factory" calibrations with the DX-4D, but not like Dolby level calibrations. These are internal and you need a voltmeter that will read in millivolts and a distortion analyzer (there are software ones that work w/ your soundcard) I think evm (the originator of hte mod linked above) has done those cals on his unit. I have not, and haven't really had any issues. It is something that would have to be done because of component drift over the years, not a level cal like a Dolby unit.
 
cabraham said:
Every dbx unit I've heard, onboard or outboard, exhibits some level of breathing. Later models used several bands of processing which made the breathing less annoying.
Click to expand...

I don't seem to have a problem with dbx nr. It's all about keeping your levels under control. I recommend never sending a level hotter than -1 VU to the noise reduction unit or you'll get artifacting and breathing/gasping.

Sharp jumps in level, too, will cause errors. dbx NR is not for tracking drums or hand percussion.

In general, I advise any & all users of analog recording equipment to avoid any dbx unit. Either use Dolby B, C, or S, or no NR at all. Later model machines, like a 34B, 38, etc., with premium tape (3M 226, Ampex/Quantegy 456, BASF/RMGI 911 or 900, ATR, etc.), can deliver pretty good s/n ratio w/o NR.
Click to expand...

I disagree. My 34b sounds miserable without dbx nr. With ATR tape and dbx engaged, I get zero artifacts and dramatically less hiss. Almost no hiss at all, actually.

I use a Tascam 3030, 2 track 15 ips unit w/o dbx, although it has onboard dbx type 1. The hiss is audible, but not excessive. But if I want dead silence between songs & during quiet spots, then NR can provide that.
Click to expand...

You're also using a quarter inch half track machine, which is a format that typically has a very low noise floor to begin with. For Tascam's multitrack decks (1/4" four track, 1/2" eight track, 1" 16 track) dbx noise reduction is a godsend, provided you've got your levels right.
 
lo.fi.love said:
I don't seem to have a problem with dbx nr. It's all about keeping your levels under control. I recommend never sending a level hotter than -1 VU to the noise reduction unit or you'll get artifacting and breathing/gasping.

Sharp jumps in level, too, will cause errors. dbx NR is not for tracking drums or hand percussion.

Since I play drums, it should come as no surprise why I don't like dbx. We are on the same page regarding drums.

I disagree. My 34b sounds miserable without dbx nr. With ATR tape and dbx engaged, I get zero artifacts and dramatically less hiss. Almost no hiss at all, actually.

"Miserable"? As in noisy? As I stated, analog w/o NR cannot be dead silent like digital. But unless you listen to music at high volume levels, the hiss is not a problem. For high volume listening, then I agree that NR provides audible benefit. Of course with dbx employed, hiss will disappear. During silent passages the dbx suppresses hiss very well, more so than Dolby. But when there is music playing, such as plucking of strings, or solo vocals, the background noise is quite audible w/ dbx. Each time a string is plucked, the compander rapidly changes the playback gain. The hiss volume rides up & down w/ the string plucking. This, to my ears anyway, is much more annoying than a steady consistent level of background hiss.

Dolby exhibits much less of this modulation effect. When a piano solo, or guitar picking passage is playing back, the background hiss is low & steady. At high volume it is audible for sure. With dbx, the hiss is modulating w/ the music. But in silent passages dbx reduces hiss even more than Dolby. That is my point. It's a matter of which bothers the user more. To me, live music is the reference against which all audio equipment is judged. When listening to a live performance, there is a steady background noise, such as the air conditioning, people rustling their programs, etc. Live music does not have modulation noise riding up & down in volume w/ the music volume. The residual noise w/ Dolby is akin to normal background moise encountered w/ live performances. The noise incurred w/ dbx is not natural.

You're also using a quarter inch half track machine, which is a format that typically has a very low noise floor to begin with. For Tascam's multitrack decks (1/4" four track, 1/2" eight track, 1" 16 track) dbx noise reduction is a godsend, provided you've got your levels right.
Click to expand...

Of course, the wider tracks of the 3030 have an advantage over that of the 34B & 38. But it's only 3 dB, audible nonetheless. I agree with you on that point. I was only telling the OP that dbx does indeed provide pie in the sky SNR specs, but also that there is a proce for it. Dolby is not without its flaws as well. Dolby requires level matching, & tends to magnify freq response errors. The *purest* sound results when no NR at all is used. With a wide track format, no NR is a viable option.

Also, I should mention this, that in the near future I plan to build an adapter to modify the eq curves for record & playback. My deck uses NAB eq, 50 usec playback. I can easily modify the record eq curve so that flat FR is obtained with a playback eq of 17.5 usec, or maybe even 12.5 usec. This will boost the SNR by 4 to 5 dB. When I do this, I'll post the results.

To summarize, if dbx sounds good to your ears, that is all that matters if you are the one listening to the tape. The OP's negative reaction to dbx is one shared by many many listeners throught history, including moi. Most audio buffs who've been around long enough in the analog recording era have the same apprehension re dbx. It is no surprise that every consumer cassette deck used Dolby, & a few that did use dbx also included Dolby as well. Commercial LP records & cassettes were overwhelmingly multitracked & mastered w/ Dolby. This is no coincidence. The superior specs of dbx were known since day one. But pros who listened to both systems immediately realized that the superior specs from dbx came at a price. More processing produces higher numbers at the expense of artifacts. Dolby greatly limited the amount of processing employed so that artifacts remained inaudible.

This is my conclusion. Dolby exercised great self restraint to keep artifacts inaudible, & sacrificed specsmanship in doing so. The dbx system threw all caution to the wind, going for broke re spec sheet salesmanship, putting artifact audibility on the back burner. The OP negative experience w/ dbx is not an isolated case. It is very common. Again, whatever turns you on is cool AFAIC. I just wanted to point out that dbx is not the only game in town. Non-standard eq curves, Dolby B/C/S, & sans NR, are all viable options depending on the equipment & music. BR.

Claude
 
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Nothing wrong with dbx. The OP is having problems because the unit in question is not interfacing properly with the R2R in use. I’ve found dbx to be very effective in pro and home environments. However, not all dbx NR units are created equal. Tascam did an excellent job integrating on-board dbx on many of their machines. The OP mentions the 246 Protastudio, which I’ve also owned since new. If you’re getting good results from a cassette format using dbx it’s obviously not a problem with dbx here, but rather a question of compatibility and application with regards to the DX-4D and the TEAC 3340. Follow the instructions for modification of the DX unit and everything should be peachy.

The later model Tascam open-reel multitracks with on-boarrd dbx, like the TSR/MSR series demonstrate how well dbx can deliver the goods.

Another issue is user error. Some of that is in not understanding how dbx works. Pumping and breathing artifacts can be a problem on bass heavy tracks like kick drum and bass. That’s because dbx is a broadband process. When signal is present everything opens up, so you will hear tape hiss in high frequencies, which of course isn’t masked by low frequency material. Simply cut high frequencies on those tracks and the artifacts are gone. There’s nothing up there in bass frequencies anyway, so no reason to allow high frequencies where tape his lives.

If it’s working properly dbx tends to be more forgiving calibration wise. I’ve never had issues with it while tracking.

I usually prefer Dolby for mixdown to half-track when NR is needed. I’ve used Dolby A, B, C and SR. I prefer Dolby C outboard units for use with semi-pro line levels (-10 dBu), but they are rare since Dolby stopped licensing C-Type for separate units. It was limited to integration with Cassette and some open-reel decks like those made by Fostex. Same story for Dolby S… very rare in outboard configuration.

Some Dolby units to look for in the pre-owned market like eBay:

-Sony NR-500 (2-channel Dolby C)
- Nakamichi NR-200 (2-channel Dolby B & C)
-Dolby Labs Model 422 (4-channel B, C & S)

For dbx Type-I look for dbx Model 150X (2-channel simultaneous encode/decode). Get two of these and use with any 4-track, or 4 of them for any 8-track. I prefer them to the Tascam units because there’s no relay switching involved and they go for a song on eBay. They sound great too and only occupy half rack space width wise.
 
Thanks for all the insight guys. I did mod the DX-4D and might have a go at calibration. I'll hook it back up again and try the -1 VU level with bass and drums. I won an auction on eBay for a dbx 'lot' that includes a TEAC 155, 122 dbx II and 124 (4 units all together) I'll experiment with those as well. I tracked down a TEAC AN-300 with the manual and test tape but I can't access the guy's email for an offer?

This is turning into a real adventure. Takes me back to 1981 when I had to scrounge $1000 bucks for the TEAC 144.
 
Sounding better

Wulp, I unhooked my analogue studio set up and 'benched' all the gear for tweaking. I did a total inside out clean up of the TEAC 2A mixer, did routine maintenance with A3340, mod'd the DX-4D (at least til the dbx 155 gets here) Calibrated the VUs on the mixer with the VUs on the R2R.

Recorded the bass guitar DI thru a PreSonus tube pre-amp and compressor (applied minimal comp) and also put a AKG 414 on the bass amp. Both signals were mixed together to Ch.1 (did test recordings until I got a decent mix) of the 4 track. I leveled the input of the mixer to -1 VU then thru the DX-4D and into the deck just above -3 VU. (the room sound of the bass amp added a bit of sparkle)
Played the bass parts a bit softer ... and vulla! a nice thick sound of bottom end. I also rolled off the bass eq knob to the 10 o'clock position when I recorded the bass which cut out the rumble.

Thanks for all the insight guys - I know there's better gear out there but I challenged myself to making the best of this TEAC stuff. I just love these relics. It's beginning to gel. Nothin like focus and TLC to the process. Thats what I like about analogue, fighting with the machines and using creativity with the limited tracks. :) Is this cool or what? :cool: :drunk:
 
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