Gyratec 23 "Ambler" Tilt equalizer is a tone control based on asomewhat different concept.
The G23 is a Tilt-type Equalizer aimed mainly at mix and mastering - for the situations where you have a mix that is already nearly-perfect balanced, but you want it a tad darker or brighter without messing up the overall definition.
Gentleness and subtlety were main design targets here: Nothing anywhere near surgical: Tilt and Highs at +/-4dB, mids at +/-2dB, and lows at +/-6.5dB
What sets it apart from all other tilt EQ designs is that we designed it around a highly linear 1dB/oct slope filter, so that rotating the tilt control will tilt an almost ruler-straight response curve, to a maximum steepness of 1dB/Oct.
Our reason for doing it like this is that although a standard tilt (which is basically a Baxandall control, that cuts top while boosting low and the other way around) does come with the associated phase roll that is a side effect of all analogue-domain filters. And this group delay/phase roll (which is distributed just around cutoff frequency) easily identifies the sound to our ears as "equalized".
So what we acheive in the 1dB/Oct tilt function is to "spread out" or distribute the "needed" phase roll across the whole spectrum, meaning that at any given interval, only minute amounts of group delay is apparent.
In total, it allows quite some correction without sounding "Eq'ed".
And because you'd occasionally want to correct outer ends of spectrum, we have added a gentle Baxandall tone control, shelving lows and highs, wide-Q bell mid, each at three selectable frequencies, that we spent quite some time optimizing.
G23 is stereo, single set of controls - and off course based on tubes and passives alone. Bypass is full-relay, and it has a gain trim function for easing comparison between direct and processed material.
The G23 is as standard available as 230V or 115V mains voltages - Please specify when ordering
This Tilt-Equalizer is based on two closely-matched 6N23P output stages in the feedback chain of a linear cutoff slope filter, and the topology is pure class-A. Lundahl audio transformers with internal electrostatic shielding are used for both in and output interfacing, giving a true floating input impedance of about 10KOhm, and an output impedance of less than 1KOhm.
This unit was originally intended for use with our analogue tape recorders, which means that the optimum operating levels are around that of +4dBu - and at this point you still have some 14dB up to the point where the unit starts to get tired, which happens around 15Vpp AC output - and then some before it starts sounding bad. This means, however, that you should consider checking your levels if you're running a modern-day DAW, which often comes factory set to extremely-high levels like +24 or +28 for 0dBfsd. Those kinds of levels are aimed at keeping a good safety-margin before running into digital-clip, but at the same time it's common practice (for a good reason) to try getting as close to clip as possible. A good level for use with the G23 (and for most analogue 2 gear in general) is somewhere around +10dBu to +15dBu analogue for 0dBfsd (full scale digital)
Our audio path consists of ONLY transformers, tubes, and passive components, t he power supply circuits are solid-state based though. The tubes should last for at least a couple of years - and often much longer than that. If and when changing tubes, contact Gyraf Audio for instructions on matching and proper adjustment of the unit.