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?
markus1299

Showing 4 responses by frzninvt

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.
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.
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.
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.