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DBX Anyone ?


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Curious to hear if anyone else willing to admit to reliance upon dbx dynamic range expander.

 

From my earliest days of stereo, I was always intrigued by the dbx, but they were very expensive so I could only admire from afar.  And I really didn't feel the need as I evolved to an all tube simple analog approach prompted by a chance encounter with a Fisher 500 C receiver.  Found a dbx 3BX Series 2 in the AudioMart, but never used, it sat up for a long time.  When I started to dabble in multi track, recording local bands I found it useful for the drum track as analog tape always compressed the drums.

 

When I started my second stereo life all the music was mp3.  ( I'm sure high res digital is nice, but where do those files come from ? )  Mp3s are fine for casual listening on earbuds, but were flat and lacking on the room stereo.  Then I remembered the dbx and plugged it into the system.  Now I can't listen without it.

 

For me the advantages of the dbx dynamic range expander are many:  One is the subtle yet noticeable sweetening of the sound that make mp3s listenable for me.  But more importantly it allows easy adjustment, compensation for the sound level.  Depending on the type of music and recording, some material is very high level and compressed, while others are too low level.  ( This should be apparent to all, ever been blasted out of the room by a song selection way louder than the previous ? )

 

Another advantage is about 20 db of noise reduction between songs.  Finally, the LED display is the coolest thing ever:  the LEDs bounce away from 0 db center level where no LEDs are lit, and this easily facilitates setting of the threshold level where downward, upward expansion take place, one nudges the slider for minimal activity of the bouncing 2 color LEDs.

 

TLDR:  The dbx is an indispensable part of my system, the secret sauce that one seldom finds talked about.

Technics SA800 c .jpg

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I have a PL 4000 as pictured below. I restored the main audio section years ago and now want to finish the other sections. I've been curious how the peak unlimiter and downward expander enhance the music. Overall, not a bad preamp, but it required a lot of TLC. Not a restoration for the faint of heart. Of course it is modified as well. I redesigned the power supply from Zener based to three terminal regulator and the gain IC was changed (but not plug-in compatible, had to cut traces and rewire the PCB) to a more modern low noise type op amp. 

 

The 4000 Autocorrelation Preamplifier was a collaboration design by Bob Carver and Bill Skinner. It was designed to expand or decompress the sonics of recorded material. In audio parlance, it's called dynamic headroom. In the midst of all the knobs and toggles was the four channel balance joystick.

The 4000 had the capability of controlling up to six components: a tuner, two tape decks, two turntables and an auxiliary input. It had three switched and three unswitched AC plugs. The 4000 was manufactured from 1973 to 1977. It retailed for $600 but the price rose 10 % in 1977. It's still highly sought after today.

PL 4000_1.jpg

PL 4000_3.jpg

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I had a PL1000 back in the day (the stand alone auto-correlator/dynamic range expander) and it was a very effective device with phono and tape. I held on to it into the mid to late 1980’s. Once I started listening to more cd’s than vinyl (yes, I was an early adopter) I sold it because the noise reduction and dynamic range expansion were no longer necessary to my ears. For vinyl though, it was a great piece and I enjoyed its benefits a lot.

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I have owned and used them all up to the DBX 14/10 14-Band 2/3 Octave Computer Equalizer Analyzer and the rare DBX 5BX-DS 5-Band Computer Controlled Dynamic Controller.  I feel the DBX 3BX-DS is the smoothest expander of them all.  The 3BX-III is more edgy and geared more towards tape and vinyl where the 3BX-DS is ideal for digital sources.  The best set up is to dedicate a 3BX-DS to each channel combining the inputs and outputs on each unit with "Y" adapters since the DBX units use mono triggered VCA's this works very well.  A cheaper alternative and equally nice sounding is the Pioneer EX-9000 Dynamic Expander.  Pioneer actually got it right as they use stereo triggered VCA's and the three bands are independently adjustable.  I have manuals and service manuals in digital form for almost the entire line up.  Unfortunately the Series Two unit is the least desired model.

PDR_1164.JPG

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10 hours ago, veloceleste said:

I had a PL1000 back in the day (the stand alone auto-correlator/dynamic range expander) and it was a very effective device with phono and tape. I held on to it into the mid to late 1980’s. Once I started listening to more cd’s than vinyl (yes, I was an early adopter) I sold it because the noise reduction and dynamic range expansion were no longer necessary to my ears. For vinyl though, it was a great piece and I enjoyed its benefits a lot.

My McIntosh c-32 always sounds and feels like it was engineered for vinyl records

where it does a superb job

Built in Dynamic range expander and EQ

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18 hours ago, Racer X said:

When I started to dabble in multi track, recording local bands I found it useful for the drum track as analog tape always compressed the drums

I used a plugin on an old 1/4 track stereo tape of a song I played slide guitar on in the early '70s. It helped the dynamics a lot, although it was kinda low key. Never had the money fow one of the dbx units but have kept a lookout for one.

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When I was a mobile DJ back in the mid 90's...I swore by the DBX 3BX Series 2!  It was a quick and easy adjustment that really could liven up a flat track!  My DJ group never ran a setup with a 3BX!  We also relied heavily on the Rane DC24 2 Channel Compressor / Limiter / Gate!  It did a nice job with signal processing as well!

 

I'd like to add a 3BX to my vintage gear stack but damn!  Prices are out of this world on used DBX's!

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And I will chime in again, I do not understand why a DSP version of something similar is not made today. Only reason is "very little market" for such?

David Blackmer just like PWK was a genius.

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14 minutes ago, babadono said:

I do not understand why a DSP version of something similar is not made today.

 

Do you know of a general purpose DSP "engine" that is fully programmable? It might not be a difficult programming job to emulate the DBX functions.

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40 minutes ago, Edgar said:

 

Do you know of a general purpose DSP "engine" that is fully programmable? It might not be a difficult programming job to emulate the DBX functions.

I do not but have not looked because I know I could not program it.....in the time allotted. But surely they are available, no?

Analog I/O, and ADC/DAC would have to be included in a "all in the box" solution.

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5 minutes ago, babadono said:

But surely they are available, no?

Analog I/O, and ADC/DAC would have to be included in a "all in the box" solution.

 

I don't know of any. For my system, I use a NUC Windows PC connected to a Steinberg UR824 ADC/DAC, DSP functions programmed under ASIO.

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@babadono  Thank you very much for the most relevant interesting link and apologies for the retread, I guess one should learn to search the forum some before just jumping in.  I guess most everything has already been covered many times by the forum in the past, but to us newer members it is all new.

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No worries. Just thought I would re link it so you and others would find it easier Plus I get to show off:)  I really wish I would have made a photo journal the original tear down/ re builds..I learned a ton...especially the fact that David Blackmer was a genius.

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