DBX Expander

I have recently acquired a Teac reel to reel and although it's a great machine, soundwise, it just doesn't measure up to CD or LP's in my system. I have a chance to purchase a DBX sound expander that I'm told greatly enhances the sound of the tape. I have no experience with this box at all. Does anyone have any knowledge of what this does?
The purpose of the expander is to attempt to undo some of the compression used on many recordings and add in some dynamics. dbx was the main proponent of these gizmos and made a number of flavors. The bottom of the line was a single band version that applied expansion across the whole audio spectrum. Problem was that a loud low frequency sound could cause audible pumping in higher frequency sounds. To address this dbx introduced expanders that independently expanded different parts of the spectrum by splitting the signal according to frequency range, expanding each range, then recombining them. They produced several 3 band models and one 5 band model (5BX).

On top of this they added a separate transient expander called "impact restoration", which was supposed to increase the definition of transient leading edges. In the 3 band series it operated globally, in the 5BX it operated independently on each band.

In the late 80's I owned first a 3BX and then a 5BX. They could definite add punch to flat recordings if used in moderation, but as my ear improved I heard the artifacts (pumping and breathing), and found that the devices colored the sound. The cure was worse than the disease, for serious listening.

Also the proprietary dbx chips used in these are no longer available, so service is an issue.
I agree as well. The DBX does to much pumping of the signal.
Although the ONE BAND DBX seemed to not do as much pumping as the others. Teac use to make an outboard noice reduction device for their machines as well which may have lowered the noise another 5 or 6 db without the pumping affects. If your a tweaker, you can try replacing the resistors and or the caps in the recording board, which is what I did to my Teac and had noticed a definate improvement in lower noise.But this is very time consuming indeed.
Well, I totally disagree with the 2 comments above. I have demo-ed properly adjusted DBX DS Series expanders for at least 15 "vinyl people" - and only ONE did not hear a dramatic improvement in A/B auditioning. Yes, they will "pump" if you overdo the levels - so don't overdo it.

If you bi-amp vertically, you can also just use them on the mids and highs, eliminating any bass pumping - but I have not found this to be an issue. Factors to consider here are the Damping Factor of you amps, and also the speakers themselves. Mine are sealed box bass cabinets, and pumping has not been a problem. Transmission line and ported cabinets may be more of an issue.

I consider the DBX an absolutely essential part of my system. Many of the recordings of the '70's and '80's were run through STACKS of DBX, or similar, equipment in the studio - EQ, compression, and peak limiting AT A MINIMUM! Proper use of one more quality device that attempts to reverse the "processing" on the output side does "color" the sound (that's what it's supposed to do) but not detrimentally IMO - just the opposite. They DO include op-amps in the circuit, but again, nobody who has heard mine can point out any negatives. One guy who is a hard core minimalist simply decided he liked the sound without the 3BX better, but admittedly had no rational explanation. Then on a 2nd visit, he was pretty much neutral on the 5BX. Quite a few people have bought 3BX's immediately after hearing mine.

That being said, a DBX will not elevate a cheaper, worn out, or misalignes RtR to the level you're looking for.

Unless you have much money to burn, try a 3BX-DS first. The DS version is the ONLY one to consider - the older ones are not as good. It should only cost around $200 to $225 plus shipping, on Ebay. There are lots around and they're affordable. If you don't like it, you can very easily resell it for what you paid.
A mint 5BX may cost you close to $1500 or more, so it's a bit riskier to start out with - especially if buying from an Ebay dealer and/or shipping via UPS or Fedex is part of the equation! The 5BX's Impact Restoration circuit is better, but the 3BX-DS's Dynamic Range Expansion is better IMO. So it's kind of a toss up anyway. I know someone who uses one 3BX on each channel and the results are superb.
I think Opalchip has a great point, first spend the money to get your R2R serviced and tuned up, including a check of its performance against the original spec. Heads could be dirty, worn, mis aligned. I have a number of broadcast tapes, all sound better then the vinyl. Only after making sure the R2R is okay would I move on to DBX.
DBX is no substitute for properly functioning equipment.

A 1 band DBX will be more prone to audible "pumping" than a multi band DBX, particularly with noisier recordings (tape recordings are often more prone to "hiss" than other sources).

THe secret with the DBX expanders is to have the levels adjusted properly and to not overdue it.

You may need to adjust the levels differently for different input sources with different inherent levels or even recording by recording.

When properly applied and adjusted, a properly functioning 3BX can help deliver more lifelike dynamics into otherwise compressed and artificial sounding recordings.

I've never detected any inherent coloration from the DBX itself, but of course interconnects used can make a difference so these have to be considered as a factor in the resulting sound.
I've not heard the DBX, but agree with an r2r tuneup. I recently bought a very lightly used Revox cassette deck with a boogered up $4.00 balance trim pot and am incurring additional expenses for parts and the attendant labor charge for new pinch rollers, capstan shaft resurfacing, align/clean/lube. The heads are out of spec and will also be replaced. At $260, the heads parts cost accounts for about half the total outlay. For comparison, my speaker cables cost more than this tuneup.

A certified Revox tech is doing the work.

The worth of a properly reconditioned tape source is up to you, but if you're serious about using and holding on to a classic machine, you ought to consider the expenditure. The experienced service shops for tape gear will likely become nearly extinct in our lifetime...
Thanks for all of your responses!! this is a wonderful site that I learn from each time I visit.

I have had the A-4010S reel to reel completely reconditioned, cleaned and aligned by a knowledgeable professional and I believe it sounds as new but...I'm sorry to say, just not as good as my CD or LP rigs. I've considered coming off the playback heads with RCA's to a Bottlehead tube amp but I'm told by a sound guy that a 3BX is the way to go and actually will give me better sound. Thing is he has the 3BX for sale and it has been totally refurbed but he wants $ 700 I think this is steep????

$700 is a lot.

I paid between 2-3 hundred for mine on Ebay.

Ask a lot of questions before buying used though. These units have been around for a while. Make sure everything sounds good, no noise or distortion, switches and adjustments work cleanly, etc.
First - $700 is ridiculously high for a 3bx. The best 3bx, which is the DS series, can be bought for $250 (or less) on Ebay very easily and I've never ever heard of one needing to be "refurbed". So now I'm a little suspicious of your tech guy's ethics.
Second - the heads on a 4010s should never need alignment from what I understand. They are totally fixed by attachment to a base plate. Moving them around once they have wear on them (without resurfacing them first) can screw up your playback, and possibly your tapes. You can also check whether your tech did this by popping the cover off and seeing whether the locktite glue on the set screws has been disturbed/cracked.
Read these two links carefully. Note in the 2nd thread that there are potential preamp issues:


The first this I would do is have the Reel to reel serviced. I know a Teac genius if you need a name. Even the cheapest Teacs were very good. I personally use a 3300SX and find it amazingly quiet and wonderfully dynamic. The only reel to reel that I have heard that I feel sounds BETTER is an Otari MX5050 (any version). Those are outstanding.
dbx NR (Type I or Type II) pretty much requires good equipment to start out with. The system is not tolerant with an unstable/mis-aligned tape transport, or being creative with the record levels printed to the tape. It exaggerates the problem of bad heads, intermittent loss of high frequencies, etc.
FYI, a 5bx just sold on Ebay tonight for $1100 which was actually cheap considering it's condition. I would have bid on it, just to have a 2nd unit - but I figure my wife would've ridiculed me perpetually - so I restrained myself.
Anyway, there was an interesting link provided by the seller, which is a "white paper" giving many details about the unit. Here it is for anyone who is interested:


Nice read about the dbx gear. Thanks.

The compression on the 5bx sounds useful for apartment dwellers or others that must listen to wide range recordings at lower volumes.

I have a 3bx and used to have a 118 single band expander/compressor. 1 band was rough, but 5band expansion and compression sounds like dynamite if adjusted correctly.
What a great thread!

I have a perfect 3BX-DS sitting in my closet I have not thought about in many years.

I had bought it new when CD first came out and I used to like to fall asleep listening to music, and found CD's (and later movies) to be too dynamic.
So I was mostly using it for compression, however I did like the effect of expansion for full scale listening sessions.

I am getting ready to move soon and would honestly probably have just left it on our trash floor with all the other gear I won't have space for (of course with a note indicating the stuff works)

So now I'll definitely not throw out the DBX. I'm curious to now try it - however it will be a challenge to try out since my system is currently balanced. I'll probably end up selling it however, now that I know what it's worth.
If you dial it in properly, I doubt you will want to sell it.
Looking at your system, you may not be into compression*** anymore - but the Impact Restoration on any analog recordings, when not overdone, is addictive. I have my 3BX-DS in the closet, just as a backup in case God Forbid, my 5bx ever has a problem.

***One really valuable use for compression is if you make CD's for listening in your car. By compressing, you can actually hear the quieter sections over road noise, without the louder passage blowing you away. I often wondered why I like the FM radio for car listening better than the built in CD player - that's why.
I certainly don't want to sell mine, but the 3bx-ds is very easy to find on Ebay. Seems there's at least one a week. And there IS another 5bx on Ebay right now, which is very unusual - they only show up about once or twice a year, and now there have been 2 in 2 weeks. With the economy and market diving, stuff may be coming out of closets...
The current one is missing it's remote control (which is nice, but not at all necessary), so it should go for a bit less than the last one.
DBX'ers : I own a mint DBX 117 that's been in storage for many, many years. Do you feel its worth re-installing in my rig ?

I had a similar single band 118 at one time and did not like it in general for expansion in my system...too much pumping and breathing introduced with only a single band.

I did use it on occasion for compression in order to listen to recordings more effectively late at night at lower volumes.

I do use the 3 band 3bx for expansion in my system currently and would find it hard to live without on many recordings, particularly on vinyl.

Yesterday I played a vinyl copy of "Thick As A Brick" by Jethro Tull that I recently picked up for the first time. It sounded fantastic right off save that the dynamics were noticeably compressed. I switched in the 3BX and things took off without reservation from there. It was sweet indeed!

Just so that you guys know the 5BX offers NO upward expansion! All the expansion the 5BX offers in downward. the only upward expansion you perceive is the 5 bands of indepdently adjustable impact restoration. The 5BX is more of a compressor than it is an expander. The the crap quality of CD recordings these days the 5BX is an invaluable tool to compress the way oversaturated & distorting CD's being spewed out by the music industries these days.

The 3BX-DS on the other hand does provide upward expansion and does have 3 bands of impact restoration. If you are using vinyl, tape, RTR, or MP3's the unit you may want to use is the 3BX-III it's processing style is more aggressive than that of the 3BX-DS and geared toward analog sources. It offers 12db of impact restoration vs. the 10db provided by the DS unit. That said the 3BX-III can be made to sound bad if you are too aggressive with the transition level and expansion controls so keep them moderate. The 4BX uses the same processing style as tne Series III but comes in a bigger box and is remote controllable if the owner hasn't lost it over the years.

Another kick ass thing to try is to run dual 3BX-DS units, one for each channel. The VCA's in these units are mono-triggered so you can use some quality "Y" adapters and use one for left and one for right. Make sure that the transition level potentiometers on the rear of the units are in the same positions. The difference and performance will astound you. Better defined image, tighter response, and stunning impact. I have run this configuration with dual 5BX's, 4BX, and the 3BX-DS units are my favorite combo.

It has been said that Pioneer got the expansion thing right using stereo VCA's so try a EX-9000 expander as well. It is a three band unit, the bands are independently adjustable and it has two processing styles based on the music you are putting through it. The choices are "hard" and "soft."

Another unit that operates similarly is the BBE 1002 or ARS these units focus on high level detail and also provide a "lo contour" to boost the bottom end. Alpine and many other companies offer scaled down versions of the BBE process in thier units. A stand alone version for the home is much better and will make more than a subtle difference. The Pioneer and BBE units will usually cost you less that $100.

I have used these units extensively for over twenty years and never noticed any pumping or artifacts with them. I run an all Klipsch Heritage system so dynamics are off the scale, and the level of realism achieved has to be heard to be believed. Even at levels in the 125db to 130db range in the living room. I still use a DBX DX5 CD player that has built in processing and can play any CD-R out there.

Great information. Thanks!

I have a 3BX series II I picked up for a couple hundred about a year back on Ebay that I think is worth its weight in gold when a particular recording needs it. How is that similar or different from the others?
The 3BX series II was shrunk down by the use of IC's vs. the all discrete circuits found in the original wooden side 3BX unit. This is actually the least favored unit of all for whatever reason (some say it exhibited the pumping effect), not sure if the Series II still used Stereo or Mono VCA's but the stereo VCA's in the original 3BX caused the image to wander.

I owned one for a short period of time and found no issues with it. I prefer the later models because of the addition of the "impact restoration" function which really increases the realism of the percussion attacks. As with all range expander wise use of the transition and expansion levels provide the best results.
I don't hear those issues with it either. Impact restoration would be an interesting enhancement to try, though impact of percussion is certainly improved significantly just through expansion as is with the 3bx S2. Percussion has startled me and made me jump on several recent occasions with the 3bx switched in.
I use my unit primarily for the Impact Restoration. The effect of the IR is to really open up the leading edge of sounds that already have a fast attack. High hats, cymbals, plucked strings, bass thumps really sound much more like live music. Until you A/B back and forth, you don't realize what you've been missing - once you do, there's no going back.
I totally agree when it comes to dial it in by frequency range, and adjustable independent impact level, and overall output level the 5BX has no equal. The Impact Restoration function is worth the price of the 5BX alone. The other features certainly have their place as well it is a great sounding musical piece of equipment. It also has a very elegant look to it. It's rarity certainly makes it a conversation piece.

I have heard of people using the Quantum or Quantum II to perform similar functions and over larger frequency ranges but I have never tried one myself.
Thanks guys for all the very valuable responses. I have had my A4010 reel to reel completely refurbed and my 3BX series 111 is on it's way so it should be an interesting experience through my Cary Slp05. I'll let ya know what I hear or don't hear
Since my system is balanced, and I'd like to keep it that way, could I just use one 3BX-DS for each channel? Meaning left is inverting - right is non inverting, then combine them back to XLR? I already use gear (Strain Gauge) that puts out balanced signals over 2 RCA's, and have a custom adaptor that goes from 2 RCA's to XLR.

Frzninvt - is this what you are referring to, or did you mean the signal goes through expansion twice? Please elaborate.
The VCA's in the 3BX-DS are mono triggered so dedicating one each to each channel (L & R) improves imaging, staging and definition. It also gives you the flexibility to adjust the channel expansion independent of one another.

I used 2 male RCA to a single female "Y" adapters (two per unit) giving me a single "mono" input on each unit. One for the left channel and one for the right channel. Not daisy chained. I suppose you could do it with XLR to RCA adapters.

Make sure the rear mounted trim pots for HF & LF transition are set equally on the units. You can tweak them as necessary by watching the front displays so you are getting the same level of expansion out of each unit. Having units close in manufacture dates helps too.

The 3BX-DS can be calibrated and adjusted using the Service Manual. Better capacitors in the power supply improve performance as well.
In the early 70s, I had a small, box-sized dbx unit for a short time, which I never used for tape recording noise reduction, but I discovered through trial and error that it did a fantastic job of cleaning up the distortions and surface noise on 78rpm records in real-time........I do not mean impulse or scratch noise, but rather the annoying distortions caused by having played the records previously with worn needles, as well as the inherent way 78s of the pre-war era basically just sound bad to start with.......It seemed to make those noises disappear, and the music, previously difficult to hear because of the continuous noise, would come through loud and clear, almost like magic...........I would have never believed it if I hadn't heard it for myself..........Unfortunately, I traded it in at my audio dealer for a dbx3bx, expecting it to be a "bigger and better" version of the one I had........Of course, I discovered it was a totally different animal and did not perform the functions of the little box, but I kept it because I enjoyed what it did to improve the dynamic range of LPs and FM broadcasts........I would just like to know if anyone can confirm for me what the model number was, as I cannot remember if it was the 117 or the 119, as I am considering picking one up, since they are very reasonably priced on ebay, and also if anyone can confirm its use for eliminating 78rpm surface noise......Sometimes I think I may have dreamt it because the improvement was so sensational........I mean, it practically made an unlistenable record sound almost brand-new........ Any responses would be appreciated......My email address [email protected] you in advance for any help........
With the resurgence of Vinyl, turntable and cartridge makers are on fire. Sweet Vinyl has a line of very sweet Sugarcubes that eliminate pops and clicks and noise floor without affecting the sound of the music. They are expensive at $1,500 to $4,000 for their units. But if you plan on recording your collection Sugarcube is a must.
With all this demand for vinyl, perhaps we can convince dbx to bring back a modern 5bx with today’s state of the are digital technology. Imagine fixing all the crap  that was done to records in the digital domain as well as making them as quiet as CDs.
As soon as my Sugarcube SC-1 arrives, I will be digitazing my dbx encoded discs. These discs are recognized as the best sounding vinyl recordings ever made. I can’t wait.
What does the community say? Can we get dbx to do it, or if the patents are expired, maybe the guys at sweet vinyl will make a product.
Markus, sell the reel to reel and buy yourself a bunch of records.