Very interesting read about the differences in some ssl eq's...
SSL 4000 EQ shootout
Also...
"EQ/Filters card:
There were several of these.
The original one (82E02) had brown LF knobs. The slope of the boost/cut sides altered with the degree of cut/boost. (I'm going to avoid "constant Q versus constant bandwidth" type terminology, because of the conflict between technical accuracy and user comprehension). It was an excellent design, and people liked it. HP and LP Filters were 12dB per octave.
Because it was plug-swappable, people suggested the possibility of making alternative versions. Since the Pultec EQ was always sought after, SSL developed an EQ which mimicked the Pultec's curves. They made it. they sold it. -It sounded better on paper. It's not universally loved, though it has its fans none the less. - I think it had Orange LF knob caps so that in a console with more than one EQ tye, people wouldn't make the mistake of splitting a sterep pair across different types of EQ, for example. Filters were the same as the 'brown-knob' original.
Then there was the Black Knob EQ. (82E32-?-) There is MUCH misunderstanding about what changed, but basically here's the story. -People pointed out that whenever you switched in the EQ, the filters were automatically inserted in circuit... whether you liked it or not. -Since the least intrusive filter settings still lopped everything at 20Hz and 20kHz, some significant phase shift was happening in the channel, and the top and bottom were being trimmed, even if your only reason for switching the EQ in was to shape the mid by 1dB... and the low-cut filter was the most egregious, in that people FELT the change between the EQ -even set completely flat- on a kick drum, turned up LOUD. -the 'push' of air felt different, and people were becoming very unhappy.
So the Black EQ (82E242) offered 'click' switches on the two filter knobs. -PULL switches were out of the question, since that would have been impossible to track using total recall (which only had a rotational position input to record and compare) so 'endstop switches' were used. these bypassed each filter. The EQ card was then modified to STEEPEN the cutoff slope from the high-pass (low-cut) filter, since now that the intrusion of the filter -even if you didn't WANT to filter anything- wasn't annoying people so much, they could use a more 'manly' slope, which they'd been unable to do before. A couple of small changes to minor stuff like the band-summing, but the actual EQ behavior really remained unchanged.
Then there was the G-series (82E292) EQ. Now things changed; both operationally and in terms of behavior. -It was launched as a response to the original Rupert-Neve produced Focusrite EQ, which was suddenly VERY popular. The Focusrite used limited-range frequency sweeps for the upper and lower midranges, together with a "multiply by 3" and "divide by 3" buttons. There was also a distinct 'dip' before a shelf boost (and mirrored 'bump' before a shelf cut). In addition, the Focusrite BEHAVED very differently as you increased the boost or cut... instead of the "corners" of the "mountain" (or valley, if you were cutting) staying in the same place, and the mountain/valley 'slopes' becoming more steep as you increased the peak deviation further from flat, the Focusrite kept the slopes THE SAME, and "widened the base of the mountain" by moving the two corner frequencies further apart. -O, and the Focusrite could cut or boost by 21dB per band, instead of a measly 18dB.
So, armed with this and other analyses of the Focusrite, and with an army of new engineers concluding that the SSL could use a new EQ design, the G-series was produced. The "multiply/divide by 3" buttons were achieved by re-purposing the old 'bell/shelf' buttons. Now the user no longer had a choice of bell or shelf at either the top or the bottom, and one was now permanently fixed as a bell and the other was fixed as a shelf. -For this alone, many people were unhappy with the G-series design. -But in addition, the 'widening mountain base' behaviour -while laudable when boosting, since the ear/brain has a tendency to zero-in on the steepness of a slope as somewhat characteristic to a particular 'sound'- it produced a rather nasty side effect if you were cutting. -The older EQ allowed you to 'notch-down' a note if say, a drum had a ring that was offending someone, and it was too late to fix it (fix-it-in-the-mix, anyone?) by keeping the bandwidth narrow, zooming in on the frequency and notching as deeply as you felt. It dd this without sucking out too many of the neighboring frequencies, or excessively altering the 'character' of the instrument. -the G series simply didn't let you do this... as soon as you started to notch -even on the narrowest bandwidth setting- it would widen the Q and start sucking all the life out of whatever you were EQ-ing. Subtractive EQ-ers generally HATED the G-series "upgrade".
As a result, early on into the G-series, it was 'dropped' as the standard EQ, and the black-knob variant was returned as the standard, with the now slightly tarnished G-series available as an option for those weren't bothered by its 'subtractive' performance, and didn't mind surrendering the ability to choose bell or shelf at the HF and LF sections.
G-series EQs were differentiated by pink LF knob caps.
Aftermarket EQ cards were made by AAD (Amazon Audio Developments) which were based on Amek/Neve circuitry, and Maselec, also based on Neve circuitry. There's not many of these out in the world... AAD Equalizers had red LF knob caps, and the HF caps changed from red to yellow. "
