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Buzz Audio SSA1.1

Dual Preamp
Published November 2003
By Hugh Robjohns

Buzz Audio SSA1.1Photo: Mike Cameron

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 10Ω 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!

Buzz Audio SSA1.1 rear panel.Photo: Mike Cameron

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 1.2kΩ (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 150Ω 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 1MΩ 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 3kΩ (a minimum 10kΩ 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.

Buzz Audio SSA1.1 front panel controls.Photo: Mike Cameron

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. 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 November 2003