Buzz Audio

Buzz Audio Ltd is a New Zealand based manufacturer of professional analog audio recording products. The products they produce are primarily used within the music recording industry in home and professional studios alike. All Buzz Audio products are designed by Tim Farrant and assembled by hand using serviceable components in robust enclosures designed to last a life time.
The products you will find within these pages reflect our goal to provide the end user with a unit that not only sounds great, but one that will last for many years. First and foremost we endeavour to make pieces that are original in design and not clones of other brands.

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Complete Channel Strip

Quite simply, there is no other channel strip made that has the versatility of the ARC-1.1. What you have here is a mic-line preamp, parametric equaliser and compressor-limiter that can be used in conjuction as a recording channel or, accessed as completely separate elements. The ARC (Analogue Recording Channel) is not just one piece of kit but three pieces bundled into one chassis with a clever relay routing system.
The compressor in the ARC-1.1 is the same design as our SOC-1.1 and has won favour with live sound engineers for lead vocal duties. A 5 band EQ section with 2 sweepable mid bands, high and low shelving and high pass filter deliver comprehensive equalisation. All this coupled with our low noise True Class A mic preamp delivers a very powerful analog channel package. Read on for an in depth view of the ARC-1.1 facilities.

Input Section

First up is the all important mic preamp. The ARC utilises the Buzz Audio BE40 True Class A high speed amplifiers developed for the MA-2.2 mic preamp. The BE40 amplifiers ensure accurate transient detail reproduction and very good noise performance. Another feature is the padless input circuit with a +15dB gain boost switch instead, providing a total mic gain range of +9 to +65dB. The mic load control adjusts the mic input impedance from 200 ohm thru to 5k ohms. This control provides another means of varying the tonal quality of the connected microphone. The 48V phantom power switch features a soft start circuit to avoid thumps and bangs. A direct output of the mic preamp stage is available on the rear panel allowing use of the mic pre section whilst using the ARC in line mode.

Next up is the line input stage which is either the rear panel balanced XLR input (with loop thru) or front panel unbalanced high impedance input. The line gain is variable from 0dB to +40dB. In addition, a -10dB pad can be switched into the balanced input to cater for those hot signals from D-A convertors. In addition to attenuating the input, the -10dB switch raises the input impedance from a nominal 20k ohms to 70k ohms which allows the driving device to freely deliver high level without undue distortion.

Output Section

Here’s where you select the mic or line input to feed the main output of the ARC. The output gain control provides +10dB of additional gain as well as acting as a fader. This control can be useful for setting the correct level into -10dBv devices such as computer sound cards. Also available here is a polarity reverse switch with mute in the centre position. Another switch selects normal output or side chain monitor, which allows you to hear what is being fed into the sidechain of the compressor section and therefore any EQ being applied.

Next up is the clean/tranny switch. In clean mode, the audio path is direct. In tranny mode, a steel transformer is switched into the signal path introducing low frequency harmonics and providing yet another tonal variation to the signal. The high pass filter (part of the equaliser section) features variable filtering of low frequency signals from 25Hz up to 450Hz. The filter has a musical 12dB/oct slope and can be switched into the main signal path (IN), or into the sidechain (S/C) of the Opto Compressor, or when selected to EXT, the filter is available externally via the rear EQ in/out XLR’s.

Equaliser Section

The four band parametric EQ features high and low shelving sections. The low shelf features two selectable turnover frequencies and utilises a true inductor (choke) resulting in a very tight sounding bottom end control. The high shelf offers a broad or tight shelving curve. The tight curve allows you to boost or cut the very top end without much effect to the mid band. Each section can be individually switched in to the main path (IN) or into the sidechain (S/C) of the ARC Optical Compressor. When switched to EXT, the sections are available externally via the rear panel EQ in/out XLR’s.

Following that are two MID BAND sweepable equaliser sections with adjustable bandwidth (sometimes referred to as “Q”). The BW control features a tight notch setting when fully counterclockwise. The frequency range of mid band 1 is 30Hz to 700Hz or 300Hz to 7kHz when the x10 switch is engaged. Mid band 2 sweeps from 160Hz to 3.4kHz or 1600Hz to 34kHz when x10 is selected. Once again, each midband is selectable into the main path, the sidechain of the compressor of into the external EQ path. Very VERY handy !!

Compressor and Peak Limiter

Incorporated into the ARC is a single channel version of the Buzz Audio SOC1.1 Stereo Optical Compressor and a FET Peak Limiter. The limiter/compressor combination can be set before (PRE) or after (PST) the equaliser section or out of the main path altogether (EXT). When selected to EXT, the Compressor is available for independant operation via the rear panel Comp in/out balanced XLR’s.

The comp drive control varies the amount of compression, similar to a threshold control on other compressors. Comp ratio is switched 2:1, 5:1, 10:1 or 20:1 but all ratio’s feature a soft knee characteristic. Compr release time is selectable from 100 milli-seconds to 1.6 seconds and also includes an auto position which is program dependant. Three attack time settings are available, with fast being very fast for an optical type compressor. Finally, a link switch allows linking to another ARC for stereo operation. Compressor gain reduction is displayed with a 12 element bargraph display.

The fast attack peak limiter utilises a FET (field effect transistor) for the gain reduction element and the release time can be selected fast, medium or slow. The Limiter can be independantly switched into the ARC main signal path (Post EQ) or accessed via the rear Comp In/Out XLR’s. It is always Post the compressor when used in combination. Although primarily designed to catch peak levels that would otherwise cause “overs” on digital recorders, the peak limiter can be used for some very heavy compression effects. Limiter action is displayed with a single LED.

The combination of the Opto Compressor with EQ-able sidechain and the output Peak Limiter give the ARC a very powerful dynamics package indeed. The peak limiter (always post the Opto compressor) has the ability to catch transients missed by the slower opto action thereby providing a near zero attack time compressor system.

Other Stuff Last but not least is the meter select switch which displays on the 12 segment bargraph the input level (ie post the mic/line gain stages), or output level (what is leaving the ARC main output). The meter can also be switched off. The over led is driven by a circuit that monitors audio level at critical points within the ARC-1.1 signal path and will light when levels exceed +20dBu.

Finally a power on/off switch completes the picture. Not immediately apparent to the reader maybe the unique flexibility of the ARC. With all the connection options available, the ARC may be used as a seperate Mic Preamp, DI Box, Equaliser and Compressor (optionally with sidechain EQ), all at the same time.

External Path Frequency Response

Compressor External Path (no Limiter) – 5Hz to 250kHz (-3dB)
Compressor External Path (with Limiter) – 5Hz to 80kHz (-3dB)
Equaliser External Path (with all EQ zeroed and no HPF) – 5Hz to 200kHz (-3dB)

Total Harmonic Distortion

Mic Input to Mic Direct Out – 100Hz=0.005% 1kHz=0.005% 10kHz=0.015%
Compressor External Path (no Limit, no GR) – 100Hz=0.01% 1kHz=0.004% 10kHz=0.006%
Compressor External Path (with Limit, no GR) – 100Hz=0.01% 1kHz=0.01% 10kHz=0.02%
Compressor External Path (10dB of GR @ 20:1, Rel at 16, +10dB Make Up Gain) – 100Hz=0.15% 1kHz=0.15 10kHz=0.18%
Limiter in External Path (10dB GR, Release Slow) – 100Hz=0.2% 1kHz=0.08% 10kHz=0.18%
Bal Line Input to Main Out – 100Hz=0.0015% 1kHz=0.001% 10kHz=0.001%
Bal Line Input to Main Out with Tranny – 100Hz=0.3% 1kHz=0.05% 10kHz=0.015
Instrument Input to Main Out – 100Hz=0.08% 1kHz=0.025% 10kHz=0.025%

Noise (all measured A weighted ref to 0dBu = 775mV RMS)
Mic Input (65dB gain, 150 ohm source impedance) -71dBu (EIN 132.5dB)
Bal Line In (10dB gain, 150 ohm source impedance) -95dBu
Unbal Line In (10dB gain, 0 ohm source impedance) -100dBu
Compressor External Path (no Limiter) -90dBu
Compressor External Path (with Limiter) -80dBu
Equaliser External Path (no cut/boost) -90dBu Levels (0dBu = 775mV RMS)


Maximum Mic input level = +14dBu
Maximum Bal Line input level = +23dBu (+33dBu with -10dB Pad engaged)
Maximum Unbal Line input level = +10dBu
Maximum Output level (all outputs) = +23.5dBu

Power requirements 115V/230V selectable on rear panel
Dimensions 2U rack mount, 300mm deep

Specifications are typical of a production unit and are subject to change without notice.
0dBu reference = 0.775 volts RMS.

  • Main Path Frequency Response (measured without EQ, Comp/Limiter or Tranny switched IN)
  • Mic Input to Mic Direct Out – 3Hz to 400kHz (-3dB)
  • Mic Input to Main Out – 4Hz to 400kHz (-3dB)
  • Bal Line Input to Main Out – 3Hz to 250Khz (-3dB)
  • Bal Line In with Tranny selected – 12Hz to 100kHz (+/-1dB),+5 @ 250Khz, -3dB @ 400Khz
  • Instrument Input to Main Out – 9Hz to 300kHz (-3dB)


Two channel diode bridge audio compressor

Introducing the Buzz Audio DBC-20 two channel diode bridge audio compressor designed by Tim Farrant of Buzz Audio. The Buzz Audio DBC-20 is a new take on a vintage technique utilizing a gain reduction element of silicon diodes in a transformer coupled bridge arrangement. This element produces a desirable compression character that can best be described as tight and colourful. The Buzz Audio DBC-20 also incorporates a self-adjusting ratio whereby the compression ratio is automatically increased with deepening gain reduction. This feature allows for the control of very dynamic signals (such as vocals) in a seamless fashion.

The Buzz Audio DBC-20 audio path uses the Buzz Audio proprietary Class A discrete amplifier design in a balanced configuration from input to output.

Operation of the compressor is easy with six switched attack and release times, a big knob for the amount of compression and an output gain control. The compressor can be switched to a soft mode whereby dynamic peaks are partially retained. Another switch introduces a high pass filter to the side chain to lower compression sensitivity at low frequencies. Each channel has a bypass switch and the side chain of the two channels can be linked for stereo operation.
Gain reduction is displayed on a fast response LED bar graph meters that indicates true peak reduction levels. The Buzz Audio DBC-20 is housed in a sturdy one unit rack mount enclosure and is built entirely by hands in using through hole serviceable components.
Buzz Audio is a pro audio manufacturer based in Wellington New Zealand, and has been producing audio equipment since 1993.

  • Vintage-inspired Transformer-coupled Diode Gain Reduction Element
  • Fully-balanced Class A Amplifier Design
  • Stereo Linkable Operation
  • Self-Adjusting Ratio
  • Switched controlled Attack and Release Controls
  • Fast-response LED Bar Graph Meter with True Peak and Gain Reduction levels
  • Soft Mode to retain dynamic peaks
  • Sidechain High Pass Filter


Dual mastering Compressor

Add some real vibe to your mastering project with our take on the vintage diode bridge compressor technique.
Audio Path Color
The Buzz Audio DBC-M is a Mastering version of the popular Buzz Audio DBC-20 diode bridge compressor and offers fully switched control for repeatable settings. The diode bridge gain reduction element coupled with our innovative side chain design delivers a vintage vibe like no other. The Buzz Audio DBC-M audio path uses our Class A discrete amplifier designs in a balanced configuration from input to output with a radio steel laminated transformer to couple into the diode bridge element. This overall combination produces a desirable compression character that can best be described as tight, colorful and rich with harmonics.
Dynamic Ratio Power

In the style of compressors from the 60s, the Buzz Audio DBC-M incorporates an automatic ratio whereby the compression ratio is progressively increased with deepening gain reduction. This feature allows for the control of very dynamic signals in a seamless fashion and is also a very desirable characteristic when used on complex percussive material.
Operational Ease
This compressor is easy to get happening with six switched attack and release times covering a wide range, including an interesting auto release mode. Big knobs with 24 position stepped Elma controls are provided for the amount of compression and the output gain. The compressor can be switched to a Soft mode whereby dynamic peaks are partially retained and another switch introduces a high pass filter to the side chain to lower compression sensitivity at low frequencies. The attractive “point source” red LED bar graph meter accurately displays gain reduction and the gloss finish knobs adds to the vintage feel of the DBC-M.

Controls and Functions

GAIN – 24 position Elma switch that adds gain at the output to correct for lost level with a -2.0 to +10dB range in 0.5dB steps.
COMPRESSION – 24 position Elma switch that sets the amount of compression.
ATTACK – rotary switch with 6 settings, FAST (less than 0.5mS)-5mS-10mS-15mS-25mS-50mS.
RELEASE – rotary switch with 6 recovery time settings, 50mS-100mS-200mS-400mS-600mS and AUTO.
HARD/SOFT – adds dynamics in soft mode for times when very light compression is required.
FLAT/BASS – reduces compression sensitivity at low frequencies for more bass punch.
BYPASS/ENGAGE – hard wire unit bypass to compare compressed and uncompressed signals.
There is also a handy power ON/OFF switch and the LINK A/B which provides for stereo tracking to prevent image shift when used on the mix buss

  • Harmonic Distortion; With 10dB gain reduction (Release set to 400mS); 1.5% @ 100Hz, 0.5% @ 1kHz, 0.5% @ 10kHz
  • Maximum Input Level; +27dBu
  • Maximum Output Level; +27dBu
  • Noise; -80dBu (measured A Weighted with 10dB gain applied)
  • Gain; variable -2.0 to +10dB in 0.5 dB steps
  • Frequency Response; 6Hz to 400kHz measured no gain reduction
  • Harmonic Distortion; At +10dBu input level, no gain reduction; 0.28% @ 100Hz, 0.25% @ 1kHz, 0.15% @ 10kHz
  • Standard Operating Level; +4dBu
  • Size; 1 Unit 19″ rack mount, (482Wx44Hx250D)
  • Power requirements; 230V/115V selectable, IEC detachable power cable.
  • Specifications are typical of a production unit and are subject to change without notice.
  • 0dBu reference = 0.775 volts RMS.


Mic preamp for 500 series

The elixir preamplifier module is an excellent compliment to the “fatter” sound of many modules now available in the API* 500VPR Series format and has been designed to provide exceptionally low noise wide bandwidth amplification of microphone and instrument signals. The elixir will suit those who desire a recording preamplifier where just a slight amount of bass colour is added to the original signal whilst retaining full treble extension and a smooth midrange – warm, sweet, liquid – the perfect blend.
The elixir circuit design uses two BE40 True Class A amplifiers in a transformeless input arrangement followed by two newly designed BE50 True Class A high current audio buffers that drive a Lundahl LL1517 output transformer. The topology is balanced throughout with the transformer providing the balanced to balanced output conversion and common mode rejection.

This set up is quite different to most single amplifier 500 series preamps and ensures excellent transient response, extended bandwidth and very good induced noise rejection.
As with all our mic preamplifier designs, we like to think of them as an extension to the connected microphone – not a separate entity.
Looking at the distortion specifications, the presence of the Lundahl* output transformer adds a subtle amount of harmonic at low frequencies thereby enhancing the bottom end but without sacrificing the wide bandwith needed for good clarity and transient response in the top end.
The output configuration of the elixir results in a maximum output level of +34dBu before clipping, which means it can comfortably deliver clean audio into all analogue or digital recorders without overload.
Gain range of the microphone input is 22dB to 70dB or -2dB to 50dB with the -20dB pad selected. More than enough for ribbon microphones. The input impedance (selected with the IN Z switch) is 4000 ohms in the H position or 1200 ohms in the L position.
The instrument input on the elixir features a “bootstrapped FET” high to low impedance convertor that then feeds the elixir amplifier stages. Selection of the instrument input is automatic when a jack is inserted on the front panel input.
Gain range of the instrument input is 10db less than the mic input at 12dB to 60dB. The input impedance is switchable 1,000,000 ohms or 20,000 ohms with the IN Z switch.

  • GAIN – 41 detented pot that sets gain between +22 to +70dB.
  • PHASE – normal or reverse polarity switched at the input.
  • -20dB – this switch introduces a 20dB pad right at the mic input for high level signals.
  • METER – four leds give visual indication of peak output level
  • HI Z – selects high or low input impedance and this affect both the mic and DI input.
  • +48V – switches on the phantom power for condensor microphones and powered DI boxes.


500 series Class A Optical Compressor

The essence is a True Class A Optical Compressor designed to fit the API* 500 VPR Series rack frames offering a great feature set in a compact package. The essence will find application with those seeking a musically transperant compressor for all tracking and mixing tasks, and it sounds particulary outstanding when processing voice and bass tracks. The essence – the Heart ‘n’ Soul of your next recording
The essence control circuit design is based on the Buzz Audio SOC-1.1 Stereo Optical Compressor but the main audio path utilises our BE40 and BE50 True Class A amplifiers along with high spec Lundahl* input and output transformers. The input transformer is directly coupled to the Buzz proprietary Opto gain reduction element (completely passive input), amplified and then balanced via the output transformer – a very simple but gutsy signal path!

The essence control circuitry utilizes the Differential Drive Side Chain (DDSC) topology that was developed for the SOC-1.1. This system, which processes positive and negative audio waveform in seperate paths, provides the incredibly musical characteristic you will hear with this unit. The DDSC design also provides for a much faster attack time compared to most other LDR based optical compressors.
Simple side chain equalizers have been provided to allow the user to adjust the sensitivity of the compressor at high and low frequencies. In addition, a side chain insert point is provided for more complex EQ and compressor “keying”.
The essence consumes 2 slots within a 500 Series rack. The input/output (I/O) connectors associated with the first slot carry the main audio path. The I/O connectors associated with the second slot are used for a side chain insert point (send and return). The insert can be switched in/out of circuit and monitored via front panel switches.

Stereo Matching
We go to a lot of trouble to match up the LDR’s used in our optical compressors but due to the inherent variances in these devices we now offer the essence in stereo matched pairs. Ask your dealer for more detail.
Rack Compatibility
The essence power consumption of 120mA is higher than other 500 series modules, but because this demand is spread over two slots (60mA each) it should work fine in all available racks.
  • API* 500VPR Series rack module format – plug in and play!
  • Advanced analogue technology – not a clone or copy of products from the past.
  • Powerful fully discrete hi-bias, wide bandwidth, differential Class A amplifiers.
  • Passive transformer coupled input, transformer coupled output
  • Side chain insert point
  • Side chain monitor selector
  • On board side chain EQ
  • Unique Differential Drive Side Chain design
  • May be linked to multiple essence units within one rack
  • Switchable 10 segment VU meter
  • Frequency Response with no gain reduction = 14Hz to 107kHz, +/- 1.5dB
  • Maximum Input Level = +25dBu
  • Maximum Output Level = +27dBu
  • Total Harmonic Distortion
    Measured at 0dBu input, no gain reduction, make up Gain 0dB
    100Hz = 0.1%, 1kHz = 0.015%, 10kHz = 0.002%
    Measured at +10dBu input, 20dB gain reduction, make up Gain +15dB, Attack AUTO, Release 16
    100Hz = 0.1%, 1kHz = 0.015%, 10kHz = 0.005%
  • Residual Noise = -95dB A wtg, 150ohm source Z, make up Gain 0dB
  • Make up Gain Range = 0dB to +15dB
  • Maximum Available Gain Reduction = 25dB
  • S/C HI EQ Boost/Cut = 8dB @ 10kHz
  • S/C LO EQ Boost/Cut = 8dB @ 100Hz
  • Main Audio Input Impedance = 20k ohms, bal or unbal
  • Main Output Impedance = 100 ohms bal or unbal
  • Sidechain Send Output Impedance = 100 ohms unbal
  • Sidechain Return Input Impedance = 44k ohms bal or unbal
  • Sidechain Max Input/Output Levels = +22dBu
  • Size = (3″Wx5.25″H). Fits 2 spaces in API* 500VPR Series rack format
  • Power requirements = 120mA +/- 15-18 volts DC, as supplied by rack power supply.

Specifications are typical of a production unit and are subject to change without notice.
0dBu reference = 0.775 volts RMS


Stereo preamp

In order to capture the most accurate uncolored reproduction of an acoustic source, a microphone preamplifier must exhibit low distortion, wide frequency response and low noise. The preamplifier must also be capable of reproducing transient information without slew rate limiting and present a non-reactive load to the microphone itself. Many preamplifiers that attempt to achieve this specification are often referred to as sounding “clinical”, however we believe the MA-2.2 brings the world one step closer to achieving this ultimate goal whilst retaining a musically warm and full sound.

The MA-2.2 has a transformerless input stage designed to minimize frequency response anomalies caused by reactive loading of the connected microphone.

All gain stages utilize our own discrete transistor True Class A differential amplifiers (the BE40) to provide an amazingly wide bandwidth and fast slew rate. In fact, the internal frequency response of the MA-2.2 extends beyond 1,000,000Hz – even at full gain! (Passive filtering at the input of the MA-2.2 to limit the response to 250kHz prevents amplification of unwanted radio frequencies).
The very high speed and wide frequency response of the MA-2.2 ensures distortionless reproduction of all transients – a key factor to ensure the preamplifier does not sound clinical or cluttered in the upper midrange. The absence of the input transformer also ensures that the low frequencies are amplified smoothly, free from LF transformer distortion and phase/frequency response errors providing a “real” and tight bass sound.
Attention to the power supply design further enhances performance by providing exceptionally quiet DC power rails for the BE40 amplifier modules. The MA-2.2’s ultra low noise and unobtrusive noise spectra provides the best possible dynamic range for digital recordings with most microphones contributing more noise than the MA-2.2 itself.
In order to keep the signal path as simple as possible, the MA-2.2 does not have a instrument input and the output is unbalanced, avoiding the extra stages required for these functions. As an enhancement to the overall design, we offer a Lundahl output transformer option to balance the output and provide some additional colour without sacrificing the key design goals of the unit.

  • acoustic guitar recording
  • percussion and drum recording
  • acoustic music styles
  • string ensembles, orchestras, choirs, voice
  • Fully discrete hi-bias wide bandwidth differential Class A amplifiers.
  • Matched and selected semiconductors.
  • Transformerless input with hi-grade WIMA film coupling capacitors.
  • 2 stages of power supply regulation.
  • Individual discrete regulators for each stage of the 2 stage amplifier.
  • High quality bifurcated relays for signal switching.
  • No “DC servo” that messes with the bass.
  • Single Point Ground pcb layout.
  • 41 position trimmed GAIN control.
  • Trimmed common mode noise rejection.
  • Output Mute and Hi/Lo input impedance switches.
  • Output transformer options.
  • 2 output connectors giving access to direct out if transformers are fitted.
  • Rugged chassis construction.
  • Min Gain = +16dB (-4dB with pad in)
  • Max Gain = +65dB
  • Maximum Output Level = +24dBu unbalanced.
  • Frequency Response = 2Hz to 250kHz @ 20dB gain (-3dB).
    = 20Hz to 250kHz @ 65dB gain (-3dB).
  • Harmonic Distortion = less than 0.008% 100Hz to 10kHz.
  • Slew Rate = typically 140 V/uS, @ +20dBu output level.
  • EIN = -133.5dB A wtg, 150ohm source Z.
  • Signal to Noise Ratio = -74dBu A wtg, input shorted
  • CMNR = 100Hz-80dB, 1kHz -80dB, 10kHz-70dB internal trims.
  • Channel to Channel Crosstalk = below noise.
  • Input Impedance = 3k ohms/1k2 ohms switchable.
  • Controls = Gain, Mute, Input Impedance, 20dB input Pad, Phase Reverse, Phantom pwr.
  • Indicators = Peak Level @ +18dBu, Power On.
  • Connectors = In-XLR3F, Out on 1/4″ jack and XLR3M.
  • Size = 1 Unit rack mount, (482Wx44Hx300D).
  • Power requirements = 230V/115V selectable.


4 Channel Studio Mic Preamplifier

If you are looking for a versatile but cost effective outboard mic preamp for your project studio, then you’ve found it! We think the Buzz Audio QSP-20 represents excellent value for money and offers the professional performance of vintage brands without the vintage price tag. Using our proprietory True Class A circuitry and the exceptional Lundal output transformers, the Buzz Audio QSP-20 delivers a big honest open sound and is perhaps the best value Quad Studio Preamplifier available today.

With plenty of low noise gain (70dB) the Buzz Audio QSP-20 works really well with low output dynamic and ribbon microphones. The mic input impedance switch can subtley alter the sound from these mic types giving you another flavour.

Also included are 4 front panel high impedance 1/4″ jack inputs for your keyboards, bass guitar or anything with a pickup. These inputs use our proprietary “boot strapped” high impedance buffer stage and sound fantastic on bass.
The wide bandwidth of the Buzz Audio QSP-20 ensures transient details are preserved, excellent for cymbals, percussives and stringed instruments. The slight increase in distortion at low frequencies from the transformer adds a touch of colour – an ideal combination. The high head room of the QSP means your sounds are captured in all their glory with no nasty clipping. Made with quality components and by real hands, the Buzz Audio QSP-20 is a sound investment!

Each channel has a detented 41 position Gain control. Toggle switches select a 20dB input Pad (for both mic and line inputs), Polarity Reverse with a Mute position, High or Low mic Input Impedance and a locking toggle turns the 48V phantom power on or off. Selection of the 1/4″ front panel jack inputs occurs automatically when a jack is inserted. A peak led will light when the output level reaches +22dBu.
  • Min Gain Mic = +22dB (-2dB with pad in)
  • Max Gain Mic = +70dB
  • Min Gain Instrument = +12dB (-3dB with pad in)
  • Max Gain Instrument = +60dB
  • Maximum Output Level = +29dBu into 3k ohm load.
  • Frequency Response
    Mic = 10Hz to 200kHz @ 20dB gain (-3dB).
    Instrument = 10Hz to 120kHz @ 20dB gain (-3dB).
  • Total Harmonic Distortion
    (measured at -20dBu input, gain adjusted for +10dBu output level)
    Mic = 0.15% @ 100Hz, 0.01% @ 1kHz, 0.005% @ 10kHz
    Instrument = 0.15% @ 100Hz, 0.015% @ 1kHz, 0.015% @10kHz
  • Noise
    EIN Mic = -131dB A wtg, 150ohm source Z.
    Signal to Noise Ratio Instrument = -76dB A wtg, input shorted.
    CMNR Mic = -78dB @ 100Hz, -100dB @ 1kHz, -100dB @ 10kHz.
    Input Impedance Mic = 4k ohms/1k2 ohms switchable.
    Input Impedance Instrument = 1MEG ohms.
  • Power
    115V or 230V ac mains, switchable on rear panel.
    IEC detachable power cable.


Stereo EQ

The REQ is a combination of passive filter circuits and active amplifier stages. Parallel resonant chokes and capacitors form the frequency selective part of each band and these are coupled into the amplifier stage via the boost/cut control. The resulting equalisation is best described as “surreal” and it never sounds hard or harsh. The low frequencies remain tight and powerful with the high frequencies clear and well defined.

Many other equalizers using passive filters have limited centre frequency choices, but the REQ boasts 72 different frequencies split over four bands per channel. The high and low bands can be switched to bell or shelving mode and the two bell mid bands have two centre frequency ranges.

Each band has a bandwidth (Q) control and if the high or low bands are switched shelf mode, this control reverts to a shelf “slope” control. In addition a passive high pass filter and a variable “saturation” module are provided. The saturation module converts the REQ into a more “vintage” sounding unit by adding harmonics to the signal via the use of a steel audio transformer driven by a “single ended” old style Class A amplifier (see distortion specs below). The low frequency response is also altered by the saturation control, depending on the position of this switch.
The REQ is available in two versions;

REQ-2.2 standard recording version with +/-16dB continuously variable boost/cut
REQ-2.2 ME mastering version with +/- 8dB boost/cut via 23 position ELMA brand switches

All other controls on all versions are switched for repeatability. The high pass filter of the mastering version offers smaller steps and varying filter slopes to that on the recording version.

Taking a look inside the REQ chassis you will discover a vey high level of engineering and build quality with modular construction for easy serviceability, high quality controls, single point power supply wiring, discrete power regulators for each band – the list goes on and on. Click on the images on the left to see inside the Resonance Equalizer and discover for yourself why this product is truly unique and an investment you will never regret!

  • tracking and stereo mix bus equalisation
  • audio mastering and restoration
  • post production sound shaping
  • No other equalizer like it in the world.
  • Fully discrete hi-bias wide bandwidth differential Class A amplifiers.
  • Real choke and capacitor resonant circuits that sound fantastic.
  • 72 frequency choices per channel.
  • Individual discrete power supply regulators for each EQ band.
  • Large easy to adjust knobs.
  • High quality long life switches and potentiometers.
  • Modular internal construction for easy future servicing.
  • Mastering and recording versions.
  • Unique transformer saturation module.
  • Overall and individual band bypass switches.
  • High-end balanced input and output amplifiers.
  • Input connectors with loop through.
  • Two output connectors on each channel.
  • Rugged chassis construction.
  • Frequency Response
    Measured with all eq bands ON set flat, Saturation and HPF OFF 5Hz to 125kHz +0.2/-3dB
    See graphs in side bar above for typical eq and HPF frequency response measurements.
  • Harmonic Distortion
    At +10dBu, Saturation OFF 100Hz 0.007%…1kHz 0.004%…10kHz 0.007%…100kHz 0.013%
    Saturation ON POS-1 20Hz 1.5%…100Hz 0.07%…1kHz and up 0.01%
    Saturation ON POS-2 20Hz 1.5%…100Hz 0.14%…1kHz and up 0.01%
    Saturation ON POS-3 20Hz 1.5%…100Hz 0.16%…1kHz and up 0.01%
    Saturation ON POS-4 20Hz 1.6%…100Hz 0.17%…1kHz and up 0.01%
    Saturation ON POS-5 20Hz 1.7%…100Hz 0.18%…1kHz and up 0.01%
    Saturation ON POS-6 20Hz 2.0%…100Hz 0.22%…1kHz and up 0.01%
  • Maximum Input Level +25dBu
    Input Impedance approx 20k ohms
  • Maximum Output Level +32dBu balanced…+26dBu unbalanced
    Output Impedance approx 70 ohms
  • Input Common Mode Rejection (ref 0dBu) 100Hz -65dB…1kHz -65dB…10kHz -60dB
  • Noise all bands ON set flat -110dB below max input level A weighted
  • General
    Power requirements 115V/230V selectable on rear panel
    Dimensions 4U rack mount, 300mm deep


Stereo Optical Compressor

The use of Light Dependent Resistors (LDR) as the control element of an audio compressor was pioneered in the 1960’s and we are all aware of the value placed on those famous vintage units. The Buzz Audio SOC-1.1 was designed not to copy, but to take that signature and improve on it by offering the user more control. With 4 ratio settings, 3 attack options and 6 release times, the Buzz Audio SOC-1.1 puts you in command of the dynamics rather than dealing with set parameters.
The design of the Buzz Audio SOC-1.1 back in 1993 lead to the development of our Differential Drive Side Chain circuit which is unique to Buzz Audio and is used in all our optical compressors. This circuit processes the negative and positive portions of the audio wavefrom separately (attack and release parameters) and drives a custom four way LED/LDR gain reduction element.

This process creates a very smooth coherent compression characteristic. The Buzz Audio SOC-1.1 is perfect for recording vocals, acoustic instruments and is really cool on bass guitar. On the mix buss the SOC will provide instant glue and will never dig holes in your tracks.
One of the short comings of the LDR is it can be sluggish to respond to changes in light and therefore the attack time of an optical compressor can be quite slow. However, our side chain design incorporates a clever little circuit to speed up this reaction time resulting in an attack time of less than 1mS in fast mode. This, along with the release and ratio controls, makes the Buzz Audio SOC-1.1 a lot more versatile than vintage compressors with fixed attack and release timings.

  • Drive – variable pot that sets the amount of compression
  • Output dB – variable pot that adds gain at the output to correct for lost level
  • Attack – toggle switch with 3 settings including an excellent AUTO mode
  • Ratio – rotary switch with 4 settings for depth of compression
  • Release – rotary switch with 6 recovery time settings including a superb AUTO mode
  • Meter – monitor input or output level or amount of compression on the VU meter
  • Bypass – hard wire unit bypass to compare compressed and uncompressed signals
  • There is also a handy power on/off switch and a channel A/B link switch which is useful when the SOC-1.1 is used on stereo mixes.
  • Max Input/Output Level; +23.5dBu (measured with 2k ohm load and 0dB output gain makeup)
  • Frequency Response; 4Hz to 250kHz (-3dB points with no gain reduction)|
  • Slew Rate; 20V/uS
  • Harmonic Distortion;less than 0.008% (measured 100Hz to 10kHz with no gain reduction)
  • Harmonic Distortion; less than 0.03% (measured 100Hz to 10kHz with 20dB gain reduction, Atk-AUTO, Rel-16)
  • Residual Output Noise = typically -90dBu, -100dBu A wtg (0dB output gain makeup, 150R source impedance)
  • Channel to Channel Crosstalk = below noise
  • Standard Operating Level = +4dBu = 0 VU meter display
  • Size = 2 Unit 19″ rack mount, (482Wx88Hx250D)
  • Power requirements = 230V/115V selectable on rear, IEC detachable power cable
  • Specifications are typical of a production unit and are subject to change without notice.
  • 0dBu reference = 0.775 volts RMS.


Stereo Optical Compressor

In response to demand from our users, we introduce the Series 20 Stereo Optical Compressor – a fully discrete, Class A, transformer coupled version of the well known SOC-1.1 audio compressor. In addition to the excellent compression characteristics developed for the SOC-1.1, the Series 20 version includes additional features suggested by our users. The use of discrete electronics and audio transformers in the audio path adds a little more character to the original SOC sound, and the extra features make the SOC-20 an excellent choice for stereo mix processing.

The design of the SOC-20 includes the unique Differential Drive Side Chain topology found in the SOC-1.1, This system ensures the compressor will never over compress and dig holes in your audio.

So what’s actually new in the SOC-20? Well, we have added a side chain insert point to enable you to apply equalization and change how the compressor acts on a frequency basis. For example, cutting low and high frequencies in the side chain so only the vocal range is compressed on a stereo mix. A side chain monitor function allows you to hear what you are doing to the side chain signal. We have also included a set high pass filter in the side chain which reduces the compressor sensitivity at frequencies below 150Hz.
Perhaps the most important SOC-20 feature is the stereo Mid/Side processing mode. At the flick of a switch a discrete Class A sum and difference circuit is enabled so that Channel A now processes the L+R (sum) signal and Channel B the L-R (difference) signal of your stereo mix. This function, along with the side chain insert point, opens up whole new ways to easily manipulate your mixes and achieve the sound you desire.

  • Toasty Class A discrete signal path with flashy Lundahl output transformers.
  • On board Mid Side processor.
  • Side chain insert point on balanced XLR’s.
  • Built in side chain high pass filter.
  • Fast attack optical compressor.
  • Music recording and mixing
  • Post production studios
  • Voice overs and dialog
  • Classical and acoustic music styles
  • Live sound
  • Maximum Input Level Line = +32dBu
  • Maximum Output Level Line = +27dBu
  • Maximum Input/Output Level S/C Insert = +22dBu
  • Noise = -95dBu Stereo Mode, -90dBu M/S Mode
    (measured with no make up gain and A Weighted).
  • Gain = variable 0dB to +15dB
  • Frequency Response
    3Hz to 120kHz measured with +10dB gain and no gain reduction.
  • Harmonic Distortion no gain reduction
    0.08% @ 100Hz, 0.025% @ 1kHz, 0.02% @ 10kHz, 0.05% @ 100kHz
  • Harmonic Distortion with 20dB gain reduction (Attack AUTO, Release 16)
    0.1% @ 100Hz, 0.06% @ 1kHz, 0.04% @ 10kHz
  • Harmonic Distortion with 20dB gain reduction (Attack AUTO, Release AUTO 2% @ 100Hz
  • Standard Operating Level = +4dBu = 0 VU meter display.
  • Size = 2 Unit 19″ rack mount, (482Wx88Hx250D).
  • Power requirements = 230V/115V selectable, IEC detachable power cable.
  • Specifications are typical of a production unit and are subject to change without notice. 0dBu reference = 0.775 volts RMS.


3-Band Equalizer

A simple but effective 3 band equaliser for the 500 Series system, the Buzz Audio Tonic utilizes real inductors (chokes) in the high and low bands. These two bands are switchable shelf or bell modes and have 2 turn over frequency choices. The sweepable mid band features the Constant Amplitude Phase Shift circuit proposed my Mr Steve Dove in 1981 which has a very fluid sound. A high pass filter is also provided with two frequency choices (50Hz or 80Hz) selected by the user with jumpers on the pcb.
As with the other 500 Series modules on this range, the signal path is True Class A with a Lundahl output transformer. The Buzz Audio Tonic has a big grunty sound with stacks of headroom making it an excellent tracking equaliser and a perfect partner to our Elixir mic preamp. Add an Essence compressor and you have a complete Buzz Audio channel strip!


The low band and high band have centre detent pots for +/-15dB of boost/cut range. Toggle switches select bell or shelf mode on these bands. The low band turnover frequency can be selected to 60Hz or 120Hz and the high band 5kHz or 11kHz. The mid band frequency range of 75Hz to 11.5kHz is selected with a x1/x10 range switch. A switch for wide or narrow bandwidth (Q) selection and a centre detent pot sets the mid +/-15db boost/cut range. Additional toggles for Bypassing the module and engaging the High Pass Filter and a Peak level LED complete the picture.

Rack Compatibility

The Buzz Audio Tonic module will physically fit into all 500 Series racks, but it should be noted the current draw is 120mA, which is higher than most other 500 Series modules. This should not be an issue with most modern racks, but with older 500 Series racks it may mean only one or two Buzz Audio Tonics should be fitted along with other modules.

  • Maximum Input Level = +23dBu
  • Maximum Output Level = +26dBu into 3k ohm load.
  • Frequency Response EQ set flat = 17Hz to 175kHz (+1dB, -3dB).
  • Harmonic Distortion
  • Measured +10dBu output level = 0.08% @ 100Hz, 0.02% @ 1kHz, 0.005% @ 10kHz
  • Signal to Noise Ratio = -88dB A wtg, input shorted.
  • Input Impedance = 20k ohms approx balanced
  • Indicators = Single LED overload indicator.
  • Size = (37Wx132H). Fits 1 space in API* 500 series rack format
  • Power requirements = 120mA +/- 15-18 volts DC, as supplied by frame power supply.
  • Specifications are typical of a production unit and are subject to change without notice.
  • 0dBu reference = 0.775 volts RMS