Buzz
Audio SSA1.1 Dual Preamp
By Hugh Robjohns.
Buzz Audio's MA2.2 preamp made an excellent impression a year ago,
but does its new little brother continue in the family tradition?
Buzz Audio's high-end audio products have appeared in the pages of
this magazine on several occasions — the SOC1.1 stereo optical compressor
was reviewed in SOS May 2002, the MIA1.0 DI box in SOS August 2002
and the MA2.2 mic preamp in SOS December 2002. All of these products
are clearly designed by audio enthusiasts and with the specific intention
of delivering superb performance. They all use high-quality circuitry
— mainly using discrete components — but naturally, such sonic excellence
comes at a price, especially given the need to ship products from
the company's New Zealand base!
To address the cost issue, and enable more people to experience the
quality of this equipment, Buzz Audio have recently introduced the
SSA1.1 dual-channel mic preamp — basically a cost-engineered version
of the MA2.2. The cost savings have been made predominantly by simplifying
the design of the power supplies and the casework, and also by using
integrated monolithic circuits in place of discrete electronics in
the slightly less critical output circuitry. However, the critical
mic input stage still employs the same all-discrete Class-A circuitry
as employed in the MA2.2. Buzz Audio claim that, while there is a
sonic difference between the MA2.2 and SSA1.1, it remains fairly subtle.
The Circuitry In Depth
The rear panel of the SSA1.1 is neatly laid out. A voltage selector
offers 220V or 110V options, and is accompanied by a slim rocker switch
providing a ground-lift facility (introducing 10 ohms between chassis
and signal grounds when activated). The IEC mains inlet incorporates
a fuse holder fitted with a surprisingly large 1A fuse (for 220V operation),
which is presumably to accommodate switch-on surges — I couldn't find
any reference to the unit's continuous power consumption rating, but
I can't believe it is 220W!
Each channel is equipped with an XLR for the electronically balanced
mic input, and XLR and TRS sockets provide a balanced main and an
unbalanced direct output, respectively. The direct output is wired
with signal ground on the ring connection and chassis ground on the
sleeve, and should therefore be treated as a pseudo-balanced output
to avoid ground loops. It is worth noting that there is the potential
here to circumvent the ground lift switch and possibly create ground
loops. If an ordinary tip-sleeve plug is inserted in the Direct Out
socket, the chassis and signal earths will be connected together,
regardless of the ground-lift setting.
Internally, each channel's electronics are housed on separate PCBs,
with a third, smaller card carrying the power-supply rectification,
smoothing, and phantom power regulation. All components are full size
— there is no surfacemount stuff here. The main audio boards also
carry their own independent local power-supply regulation circuits,
although there are fewer stages than used in the MA2.2.
The discrete Class-A electronics for the mic inputs are carried on
a pair of daughterboards — presumably one for each side of the input
signal. This circuitry is exactly the same BE40 Class-A amplifier
design as used in the MA2.2, but with a fixed input impedance of 1.2k(omega)
(special input impedance requirements can be catered for on request).
There is no input pad facility, but the maximum input level is a whopping
+14dBu, so there is plenty of headroom available. The audio bandwidth
is equally generous, the specs stating a response of 4Hz to 200kHz
(at the -3dB points and with 30dB gain applied). The EIN figure is
an impressive -132dB (A-weighted with a 150(omega) source), and the
harmonic distortion specification claims better than 0.01 percent.
The instrument input is handled by another discrete Class-A stage,
this time employing a 'boot-strapped' FET amplifier, which presents
an ideal 1M(omega) input impedance. The maximum input level here is
+10dBu, so high-output keyboards should present no problem either.
The bandwidth specifications are the same as for the mic input, but
the distortion figure is slightly higher at 0.01 percent.
Rather than using discrete output stages like those on the MA2.2,
the new SSA unit employs high-grade integrated circuits — an Analog
Devices OP37G and a pair of OP275s provide up to +24dBu into loads
over 3k(omega) (a minimum 10k(omega) is required for the unbalanced
direct output). These particular op amps are amongst the best available
for high-quality audio circuits, and give surprisingly little away
to the discrete Class-A output circuitry of the MA2.2 — although the
difference can be seen in the specs. The slew rate of the discrete-circuitry
flagship MA2.2 is 140V/µs, whereas the integrated output devices of
the SSA1.1 can only manage a slew rate of 20V/µs — so transient response
is one area which suffers slightly in the new design.
If required, Sowter 8403 line output transformers can be installed
within the SSA1.1 case as an option — either by the factory or as
a user retrofit — to provide floating balanced outputs. The overall
build quality of the SSA is very good, although should servicing become
necessary it will require complete disassembly of the poorly channel's
front-panel controls before the circuit board can be removed to access
its underside.
Front-panel Controls
The front panel is laid out clearly, with identical control arrangements
for each channel plus a power toggle switch and associated yellow
LED on the right-hand side. The microphone input gain is set by a
large rotary control with a lightly detented feel, spanning +9dB to
+50dB. An adjacent toggle switch increases the overall stage gain
by a further 15dB, giving a maximum gain of +65dB. A peak LED illuminates
at an output level of +18dBu, which is 6dB below the maximum output
level of +24dBu. The peak indicator can be recalibrated to a different
level via an internal trim pot, if required.
The DI input has its own rotary level control which also has a detented
action like the mic input, but this time spanning a gain range of
zero to +40dB. The 15dB gain switch doesn't affect the DI input. Plugging
a source into this DI input automatically mutes the mic input, so
that the DI takes priority. Although an unbalanced input, the front-panel
socket also accepts TRS plugs, as the ring and sleeve terminals are
both connected to ground.
The simple channel controls are completed with three toggle switches.
The first applies a 50Hz high-pass 18dB/octave Bessel filter which
can be used with both mic and DI inputs to help remove rumbles — very
useful on a preamp which is flat to 4Hz! Skipping ahead to the third
switch, this applies +48V phantom power to the mic input, and is equipped
with a soft ramp facility to help minimise switch-on thumps (although
many mics generate power-up thumps internally anyway). There is, surprisingly,
no warning lamp associated with this switch.
The middle switch is a three-position type, which is marked as providing
'normal' signal polarity for the balanced output when in the upper
position. The middle position provides an output mute, while the lower
position is supposed to invert the output polarity. However, my trusty
Terrasonde Audio Toolbox test set revealed that, in fact, the balanced
output of the SSA1.1 supplied for review was inverting in the Normal
position, when comparing the output signal with that arriving at the
mic input. [Note - this problem has since been fixed in all SSA
units].
The polarity switch doesn't affect the phase of the unbalanced Direct
output, which is always supposed to be in phase with the input, and
a little further investigation revealed this to be the case. The DI
input was also of the same polarity as the mic input. This evidence
all points to a simple wiring error in the balanced outputs — something
which is easily cured. For the auditioning I used the unit with the
balanced outputs switched to the reversed polarity position, to ensure
absolute polarity was maintained, allowing direct comparison with
my other preamps.
There is no LED indicator to warn when the output mute mode is engaged,
so there is some potential for confusion here if the polarity switch
is accidentally knocked to the central position. Incidentally, the
balanced output is muted during powering up and down, but the unbalanced
output isn't, so loud splats or thumps may be heard on this output.
So How Does It Perform?
I continue to be impressed with Buzz Audio's products, and the SSA1.1
is no exception. This is a very high-quality mic preamp, sharing many
of the same qualities as the flagship MA2.2. Like that model, the
SSA1.1 has a similar dynamic, detailed and fast sound, with the same
sense of a neutral and very open character. Using my own GML8304 mic
preamps as a reference, the SSA fared extremely well, and is clearly
a fine performer. Unfortunately it wasn't practical to A/B the MA2.2
and the SSA1.1 side by side, but in comparison with the GML, I don't
think the SSA1.1 gives much away to its older sibling. The bottom
end still sounds big and, while transients from acoustic guitars weren't
quite handled with the aplomb of the GML, there is nothing really
to criticise here.
Using the SSA1.1 with a single mic or an independent pair of mics,
I found the gain adjustment resolution to be perfectly adequate —
the actual gain change per detent step varied across the range of
the control, but was slightly more than 1dB in most cases. However,
using the SSA1.1 with a pair of my favourite Sennheiser MKH40s in
a simple crossed-pair arrangement, the control detents often made
accurate gain matching impossible — the gain matching between channels
with supposedly identical settings varied by up to 0.6dB. This may
not sound like much, but accurate alignment of crossed pairs typically
requires matching within 0.25dB, which often proved impossible to
achieve on the SSA1.1. I don't recall this being an issue with the
MA2.2, and it may not concern many users anyway, but it may represent
a significant drawback to others.
The preamp has a very neutral sound, tending to sound slightly larger
than life perhaps, but not in an overt way. It is bright and detailed
at the top end, sounding open and well controlled, while the bass
is full and wonderfully extended — an organ recording using spaced
Sennheiser MKH20s certainly gave my PMC monitors a frightening workout!
The DI input also tended to make instruments sound full and rich —
extracting the most from any source, with a well-judged gain range.
The SSA1.1 is a well-designed, well-built mic preamp of superlative
quality. The cost-cutting compromises have been chosen well, so that
very little of the sonic excellence has been lost. There is roughly
a 25 percent cost saving in the UK between the SSA1.1 and the MA2.2,
but perhaps only a 10 percent quality reduction. As a result this
is a very worthy addition to the range of superb, cost-effective preamps
now available, and it offers strong competition to the likes of the
Focusrite Red 8, DACS Micamp and Amek DMA.
Published in SOS November 2003 TOP
