help with understanding the Empirical Labs distressor circuit. (gut shots)

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MGC1

Member
Joined
May 14, 2012
Messages
8
I would like to know a bit more about this particular device as there seems to be very little info on the internet about it. By looking inside I noticed they have gone to great extents to stop any body knowing what OP-amps they are using (special op-amps??) by painting over all the numbers on the top. the same with all the transistors.

I was hoping to find out if they use the same F.E.T. as the 1176LN. also there seems to be a lot of diodes, imagine some are for rectification in the side chain, but are others used for clipping? this thing can produce some heavy distortion! I noticed an LED on the circuit-board, again could this be for asymmetrical clipping? Also as there is no threshold control, i'm guessing that is has a fixed threshold, a bit like the 1176 however I did notice on the board some resistors that looked as though you maybe able to customise the threshold, with swappable resistor boards(is this true). It would be very much appreciated if people could share any knowledge with me to give me a better understanding of what's going on inside the box.

Thanks everybody.

 

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Manufacturers can't really stop the Internet, so don't worry about posting pictures. We generally do refrain from cloning currently available original designs, but this is not one of those. The Distressor is an IC-based, transformerless version of the 1176, with the addition of filters and digital control (I like that high-pass sidechain filter, but really hate cycling through ratios). There was a thread about this a while back; do a little searching. As for theory of operation, I've never been inside either unit, but I believe they are FET-based variolossers. I could be wrong. The diodes are most likely for the sidechain (as you mentioned) and the metering.
 
I think this is a digitally controlled compressor, so maybe some latches, clocks, any CMOS logic?
 
MGC1 said:
...there seems to be very little info on the internet about it. By looking inside I noticed they have gone to great extents to stop any body knowing what OP-amps they are using (special op-amps??) by painting over all the numbers on the top. the same with all the transistors. I have heard about this kind of stuff before usually involving guitar pedal makers sanding off all the colourcodes from the resistors on the circuit.

Another similarity Empirical Labs shares with guitar pedal makers is that they're not re-inventing the wheel, but merely devising clever control implementations for the end user. In the case of the Distressor, the controls are clearly a reference to those of the 1176, with the addition of filters for the audio & sidechain signals. Another difference is the fact that the Distressor controls these, along with the ratio, through digital switching (i.e. clocks & CMOSes). The other big difference (as I mentioned earlier) is that the actual functioning of the circuit is based on that of the 1176 as well, but made up of ICs as opposed to FETs. I suppose that might make it a VCA compressor, but you did get that from the manual, which was more likely written by their marketing department than their engineering department.

In my opinion, all of the additions can be accomplished using mechanical switching, and the user experience would benefit from this by not requiring the user to cycle through switch options. So the change to digital controls is really one of cost effectiveness. And, as you pointed out, the TL072 is not exactly the pinnacle of IC technology. I always found it fine in guitar applications, but after you pointed out these are in there I can now see why I always held in the back of my head that the Distressor has the bandwidth of a guitar pedal. So the change to TL072s & such from the 1176's discrete circuitry is obviously a cost-cutting measure as well. This compressor is more-or-less a cheaply made 1176. So there's some meat for your report. Talk about the engineering feats accomplished to bring a cheaper version of the 1176 to the masses (and they're probably seeing higher margins than UA is seeing on the 1176 repro), which the masses have welcomed as a good-sounding and very usable piece of gear.

Also, since info on the Distressor is scarce, as you pointed out, you might want to look into circuits for 1176, revisions G & D/E, and you'll find more people talking about this. It might be easier for you to have an understanding of what's going on inside the more known of the two variables before delving into the more uncharted territory of the Distressor.
 
A True Sound "Bottle Neck" !!! ( I.M.H.O. )

Had a couple (matched) during  a mixing session some year ago....
turned both off ,
after some minute of  test on some track (recorded at 24/96 range)
coming out from a "rosetta" (24/192khz) with clock at 24/96

the compression "action" and "variability" of the same
are not so bad ,
but the sound that go to the input
it's not the same at the output
loses too much integrity ( I.M.H.O.  and the other musician guys too ..... present at the session)

peace
R.
 
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