dbx 119 Story...

sweetbeats

Reel deep thoughts...
So my Dad gave me a couple of these...he got them at a garage sale some time back for $5 or $10 apiece.

I was at his place looking through his varied collection of audio stuff and came upon them. He asked if I could use them and I said "I'm sure I can figure something out..." and he said "take 'em!" So I did. :D

For those of you that don't know, the dbx 119 (also very similar to the 117) is a compander originally designed for the home hifi environment, primarily to expand the dynamic range on compressed pre-recorded performances. Think of the classical music enthusiast back in the day who had a nice listening system, but wanted to experience the original dynamic range which was compressed to maintain the limits of the vinyl pressing. Well now he/she could pipe their playback through the 119, expand the compressed pre-recorded audio and experience a dynamic range closer to the original performance. dbx included the ability to compress as well as expand with the 119, hence "compander".

Anyway, the neat-o thing with the 119 is that it utilizes the very same proprietary VCAs as a well-known highly desirable vintage dbx dynamics processor.

I'm not sure yet how I'm going to use these things, but "I'll figure something out." :)

One of them is in better shape than the other, and I started doing some digging around to find there are some mods that can be done to "improve" things. I was planning on recapping one of them, and then started thinking of modifying by upgrading the audio driver opamps and some other things.

Fortunately the one in better condition also has better stock opamps. I say this is fortunate because two of the five opamps are "internal" drivers for the VCAs, and you don't want to mess with those unless you can recalibrate the thing. I can't. So its safe to assume that the "better" opamps that I'm not going to replace provide for better processing. The one I'm leaving alone has 741 chips in it. The one I'm modifying has LM301 chips in it. As I said, there are five of them: input audio driver, output audio driver, Threshold LED driver, and the aforementioned VCA process drivers. I'm replacing the two audio drivers with 5534s.

Since the 119 audio circuit runs at unity gain, a compensation cap is required for the 5534 to maintain stability at unity gain. I will also bypass the power rails at each opamp. Also, each opamp uses a 33pF ceramic in its feedback loop and these all look like they're heat-stressed so I'm going to replace those.

Other things I'm gonna do:

  • Recap with good quality Nichicon 105C parts with an increase in filter capacitance
  • Add HF bypass caps to the filter caps
  • Replace the discrete rectifier diodes which look DINKY on this thing...I'm putting in IN4007 parts...overkill...but its what I have here...
  • Cosmetic detailing including sanding and refinishing the REAL WOOD side panels ;)

Here it is:

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The guts:

IMG_2304.JPG



The proprietary VCAs are in the silver boxes. Very few electrolytic caps...and if I'm reading the schematic correctly there are NO ELECTROLYTIC CAPS IN THE AUDIO PATH. :eek:

All the caps are related to the power supply, except for two, and they are for timing of two of the VCAs.

Its a really elegant and simple design with very nice quality components...and those two big knobs on the control surface are nice heavy chunky metal.

Anyway, stay tuned.
 
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Ooo, Cory, I wouldn't touch those. They sound sooo good in their stock, original condition. Just my 2c...

PS: I'll take one off ya, if you're interested in selling. :)
 
Hey Daniel! :D

What I'm doing will do nothing to what the 119 does and how it does it...it'll just help the audio to maintain some clarity and mostly to reduce the noise floor...the heart remains untouched.
 
Ooo, Cory, I wouldn't touch those. They sound sooo good in their stock, original condition. Just my 2c...

In fact, nothing different happens with the audio coming in because the audio hits the VCAs right away. The only opamps being replaced are the output drivers. I was incorrect in my first post...there aren't any opamps at the input stage.
 
Wood panels are refinished, mods are all done to the guts. I want to replace the screws and washers that fasten the side panels to the chassis with stainless parts, but other than that it's done.

Here are the revised guts:

image.jpg

Here's a closeup of the underside beneath the sockets for the new opamps...it was a little tricky because there used to be a comp cap between pins 1 and 8 of the LM301, and there are solder lands for that, but the 5534 calls for the comp cap between pins 5 and 8, plus I added the power rail bypass cap between pins 4 and 7. It all worked out okay.

image.jpg


I'll post some more pics when it's all put back together, plus some impressions of its performance and maybe some comparative detail between the unmodified and modified units.
 
I got a dbx 118 a little while ago for free at a garage sale. I had to re-cap it and I left everything else intact.

A nice unit.
 
I have been using one of these for the past few years with my 388.
It's kinda cool. I find it adds a little colour to the sound source. Mines not that noisy either. Did you have those upgrade parts just kicking around, or did you order them?
 
I've only got a bit of experience with the newer versions of that unit, the 1BX DS and the 3BX DS which were purely dynamic expanders, no compression. The 1 was a full band processor and the 3, 3 separate processors each one tuned to lows mids and highs. The 3BX was definitely a far better unit as it seemed to sound more natural but was also far more expensive. On individual instruments, I'd assume a one band unit would still yeild some pretty good results. On pre-recorded material though, it be a bit lacking unless its used with conservative setting.

From a purely cosmetic viewpoint though, the older, made in USA stuff with the wood panels were definitely classier looking units!

Cheers! :)
 
I have had one of these, a 117, in my rig for a while now... it gets used a lot as an expander on drum tracks!! If you have a dampened snare track with blaringly loud hi-hat leakage (as played by all drummers who are not also recording engineers) it does a great job cleaning that up at a ratio of about 1.6. The detector is really, really fast and the box has tons of headroom for something that looks like home stereo equipment.
 
Post some links, love to hear a/b some before and after examples. You guys are excellent writers, but in my humble opinion, the dbx 117,18,19 boxes are all junky useless pieces of crap.
 
The 119 isn't a noise reduction unit...its a compressor/expander...I can use it with ANYTHING!! :D

Yes and no. These dbx units can be used as NR units because they use the same kind of compression/expansion Companding as dbx Types I and II. dbx NR is a compander, but the settings are not user modifiable. With units like the 119 you can experiment with ratios, or you can set up like NR, which is what these were commonly used for back in the day... basically ended up in a dbx Type II role for recording. But these are certainly more fun plain NR because you can experiment. ;)

Love the look of these things... I guess that makes me "Old" (Or at least older)
 
Yes, the panel markings on the 117 indicate that one of the intended uses was for tape noise reduction (straight companding) at a compression/expansion ratio of about 1.4 - but you can't feed it a dbx type I encoded signal off your multitrack (I have tried this) and get correct expansion, because dbx I and II incorporated extra pre-emphasis and stuff in the detector sidechain to reduce the apparent level of modulation noise.

I used it to lightly compress some cassettes I was recording for the car and it worked well, it is extremely transparent sounding on a whole program.
 
Yes, the panel markings on the 117 indicate that one of the intended uses was for tape noise reduction (straight companding) at a compression/expansion ratio of about 1.4 - but you can't feed it a dbx type I encoded signal off your multitrack (I have tried this) and get correct expansion, because dbx I and II incorporated extra pre-emphasis and stuff in the detector sidechain to reduce the apparent level of modulation noise.

Correct, you can't use dbx Type I and II interchangeably and you can't use either one with these early companding units, but you can use the dbx 117, 119, etc, for noise reduction just like you would use dbx I and II (encode/decode) and the results will be most comparable to dbx Type II.
 
....but you can use the dbx 117, 119, etc, for noise reduction just like you would use dbx I and II (encode/decode) and the results will be most comparable to dbx Type II.

This interests me. I have a dbx 118.

How can I use it for noise reduction for my mixes to the Tascam 42?
 
Couple shots of the 119 back together:

photo 1.JPG

photo 3.JPG


Ghost, if you *did* want to do something with them for a certain sticky thread you authored, of course feel free. Not saying you need to, but I think you know how to find the pics of you *want* to. :D
 
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