Gyraf Audio Gyratec 23-S User manual
Gyraf G23-S Tilting Equalizer
Gyraf Audio Gyratec 23-S "Ambler" Linear Tilting Equalizer.
Preliminary user manual, 17. May 2018. Edit May '20.
The Gyratec 23-S Tilting equalizer is a tone control based on a
somewhat different concept. Instead of going with standard 6dB/oct
"first order" filters with their inherent phase/group delay around
cutoff frequency, we approximate a 1dB/oct filter which
distributes the (necessary) phase clutter over eight octaves. This
results in a very unobtrusive response - even at extreme settings
the material will tend to stay in balance and subjectively sound
unprocessed.
On top of the tilting tone control, we have added a very-gentle
Baxandall tone control with shelving lows and highs and a bell
mid, each with three selectable corner frequencies.
Our interpretation of the the "Tilting" equalizer does not have
selectable corner or rotation frequencies, as the linear approach
makes this unnecessary.
The -S addition for the G23 designates an added solid-state
architecture – with the bypass switch in the “S” position, we
bypass the usual transformers and tubes, and wrap the tone control
circuits in servo-balanced active circuits instead. This for
situations where you need the enhanced cleanliness or huge drive
capabilities of solid-state.
In use:
First of all, when turning on the Eq, allow the unit to heat up
it's tube department for ten to fifteen minutes - to get the tubes
stabilised in their working temperature. The sound and operating
levels for the non-S setting will change slightly within this
period.
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The Gyratec 23-S works as follows:
The unit is stereo, single set of controls - based on dual-
technology: Either tubes and transformers – or fully solid-state,
with servo-balanced in- and output. Bypass is full-relay, and the
G23-S has a “TRIM” function for easing comparison between direct
and processed material.
The inputs are floating transformer balanced, 10K Ohm "bridging"
type, or 24KOhm servo-balanced. The input and output connectors
are standard XLR jacks, pin 2 hot. Outputs are floating
transformer balanced with a source impedance of less than 500
Ohms, or servo-balanced at less than 50 Ohm source impedance.
The main feature of the unit is the "Linear Tilting" knob (1). At
centre position it acts bypassed, providing linear transfer
through the unit. Turning the knob clockwise will gradually boost
higher frequencies while attenuating lower frequencies - and the
opposite way when you turn it counter-clockwise. At the end of the
knob travel you have a maximum of 1dB/oct - which equals to ca.
+/-4dB at the outer ends of the audio spectrum.
On top of this, we have the simple Baxandall tone control with
three boost/cut controls (3), centre detented and neutral when
centered. The available boost/cut amount is +/-6.5dB on lows,
+/-2dB on mids, and +/-4dB on highs. The curves are VERY gentle, a
wide bell for the mids and wide shelves for the high/lows. The
desired frequency range of the Baxandall part is set by the
frequency controls (2), each with three selectable frequencies.
No, we won't tell you where the frequencies are - but we spent a
good deal of time on optimizing both frequencies and boost/cut
range for best performance in the "unobtrusive" category..
(4) is your Bypass switch – it select solid-state (“S”) or tube
technology (“IN”)- and when set to “OUT”, it takes the entire
electronic circuit out of your audio path, and shorts the input
XLR's directly to the output XLR's by means of a relay. You don't
want eq, you don't get any..
The "Trim" control (5) is a control for fine-tuning the gain of
your processed material, making it easier to perform a same-level
comparison for judging sonic performance.
Last, the Power switch (6) to turn off the unit when it's not in
use. Tubes lasts long, but not forever.
Technical:
This Tilting-Equalizer is based on two closely-matched ECC88
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. Solid-state part behaves like such should.
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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 tube side of 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 to try getting as close to clip as
possible for loudnesswarrific reasons. A good level for use with
the G23-S (and for most analogue gear in general) is somewhere
around +10dBu to +15dBu analogue for 0dBfsd (full scale digital).
Note, that the solid-state path of the unit does not really care
much about working levels – but listening tests indicate that even
this sounds best at levels discussed above.
Our audio path, in “real mode”, consists of ONLY transformers,
tubes, and passive components. The power supply circuits, and off
course the solid-state audio chain when selected, 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.
Important notice:
Do not open this unit, as there are really high - potentially
lethal - voltages present inside. Refer servicing to qualified
personnel. If trimming the unit, it is of primary importance to
use insulated tools, as lethal voltages are present on exposed
surfaces related to the trimming procedure. Do NOT try this
yourself, unless you’re absolutely sure what you’re doing.
You can safely remove the four rubber feet if you wish to mount
this unit in a tight rack - please save the feet AND screws for
future use, do NOT use longer screws than the supplied M3x5. NOTE:
The feet are the ONLY part that can safely be removed. Do not
loosen any other screws!
For long tube life, switch off unit when not in use. Don’t leave
it on all the time - it won’t suffer from being turned on and off
regularly.
This unit operates from 220-230V AC, consumes about 35W, and the
mains fuse is a 630mA slow-blow type. For the US-version, marked
“CE 115VAC”, the operating voltage is 110-120VAC, and the fuse is
a 630mA Slow-blow (“T”) type.
For further questions, comments and wishes, please contact Gyraf
Audio:
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Declaration of EU-accordance
I, the undersigned, hereby declare that the following device observes the protectional demands stated in the Council’s
directive 89 336 EEC about electromagnetic compatibility (EMC) and the Low Voltage Directive (LVD).
Identification of device
Category: Audio Equalizer
Make: Gyraf Audio
Model type: Gyratec 23-S Tilting Equalizer
Name and address of the undersigned:
Jakob Erland
Gyraf Audio
Jægergårdsgade 154C
8000 Aarhus C.
Denmark
Standards founding this declaration:
EN 55013, EN 55020, EN 61000-3-2, EN 61000-4-2 and EN 60065.
Remarks:
The CE-mark only states accordance with the EMC-directive 89 336 EEC and the Low Voltage Directive, LVD.
Århus, May 2018
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