Anthony Gallo Reference 3 S.A. Amp - Manual (Page 4)

Why do you offer crossover points up to 200Hz if 40Hz is the natural speaker rolloff?
Because you can also use the SA with other makers’ passive subwoofers or speakers which may require
bringing the SA in well above 40Hz – more on that below.
Do I need to worry about the phase controls?
Usually you will set these phase controls to 0. This avoids bass cancellation and timing errors. The Ref³
loudspeakers are minimum-phase time-coherent designs. They don’t require any phase adjustments to exhibit their
remarkably transparent performance. Like the higher crossover frequencies, this feature is only included for
applications with speakers other than our own – with one exception.
If your room were heavily asymmetrical, one Ref³ speaker might end up being positioned far closer to a
sidewall than its mate. This would cause bass reinforcement in one speaker but not the other. To overcome some of
this audible imbalance, a careful adjustment on the phase control of the imbalanced speaker (together with the
appropriate crossover frequency) will introduce some deliberate frequency-specific out-of-phase cancellation. Set
correctly, this can address the most severe frequency response peak. However, this is an advanced application that
will require lengthy experimentation by ear to get right. Ideally, a dealer or custom installer who takes some
acoustical on-site frequency response measurements to scientifically assist in the process should perform it.
What about the EQ function?
The SA includes an EQ cut/boost from –3dB to +6dB and in 1dB increments. This includes 0 or bypass.
Careful employ of this feature can extend bass response of our Ref³ to 22Hz flat. That is true no-compromise
subwoofer bass in full stereo. With the SA, you categorically do not need a separate external subwoofer. The EQ
only affects the frequency range below the crossover frequency you’ve selected on the front panel. In most cases,
this will merely be the bottom octave of 20-40Hz (unless you decide to set the crossover frequency higher).
Depending on your room and speaker positioning, you may not need any additional bass boost outside of driving
the 2
nd
voice coils directly. Remember that our ‘twin-drive’ scheme already is a major bass boost in and of itself. It
will be sufficient in most environments. Whether you need/want to set the EQ control into the active gain range
above 0 will depend on your room. It will also depend on your main amplifier that drives the speakers’ upper
input. If your main amplifier is unusually bass-shy or a lower-power tube design with limited bass response, the
usual flat-to-40Hz extension of the Ref³ without a second amp could already be compromised. In such a case, the
additional boost of the EQ circuit can restore this lost bass. However, adjust by ear and to personal taste just as
with the crossover control setting
What about the volume controls?
Next to the crossover control, this is the most important feature of the SA. Whenever you bi-amplify even
in a regular scenario, you must have a means of trimming gain on the second amplifier if it isn’t identical to your
main unit. Because the bi-amp scheme of our Ref³ speakers is far from conventional, this attenuator feature
becomes even more important. Let us highlight another unique aspect of our approach to bi-amping (which,
unfortunately, only works with our speakers).
Have you ever heard of the old “tubes on top, solid-state on the bottom” idea? In a nutshell, it refers to
capturing the “sweetness” of tubes for the midrange and treble and the “muscle, grunt and control” of high-current
high-power transistor amps in the bass. Besides issues with gain matching (which can be overcome with amplifiers
that have their own level controls), this mix-and-match approach of different output devices and sonic signatures
creates very audible discontinuities of harmonic envelope, timbre and texture in a speaker that is supposed to speak
with one single voice, not many different ones.
Our SA’s unique flexibility complements your main amp to perfection and without creating sonic
discontinuity. How so? Remember that your main amp runs the speakers full-range. That includes the woofer to as
low as it reaches (40Hz flat and lower depending on room and setup, all from the 1
st
voice coil alone). The sonic
signature of your main amp of choice (tube, solid-state or digital, high-power or low-power) thus affects all
frequencies seamlessly top-to-bottom. The SA merely fills in the very lowest octave with high-current, high
damping-factor transistor muscle. In audiophile speak, it runs in “parallel” or simultaneously with your main amp