pro-audio products

advanced recording channel strip

vocal tracking compressor

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design features

Imagine a analog recording channel with eq and compression that can be used as a channel strip, or as completely separate elements...

versatile investment

Quite simply, there is no other channel strip on the planet 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 is not just one piece of kit but multiple pieces bundled into one chassis with a clever relay routing system so you can assign each element to the main signal path or to externally accessed I/O.

audio path strengths

The signal path of the ARC utilizes high end audio opamps from Analog Devices which have been selected for their wide frequency response and naturally warm sound. These devices are also used in our SOC-1.1 compressor, which has been likened by many to sound like a tube unit. The mic preamp input uses our BE40 True Class A amplifiers to provide impressively low noise at high gains. The output section of the ARC includes a switchable steel core transformer that adds a more vintage sound if so desired.

creative control

The extensive equalizer section includes a variable high pass filter, two parametic mid bands covering the full audio spectrum and bass/treble shelving bands. The compressor is a clone of our famous SOC-1.1 opto design and attached to that is a very fast FET limiter. Even more powerful, each band of the eq can be assigned to the side chain of the compressor for frequency dependant effects. Read the controls and functions section below to find out more about the creative versatility of the ARC-1.1.

controls and functions


vocal mic preampFirst 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.


bass mic preampHere'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.


audio parametric equalizerThe 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 limiter

bass compressorIncorporated 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

recording channel stripLast 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.

user comments

Sven "Samson" Geiger

For years I've been using my good old Audio Design Vocal Stresser which is really an old timer right now. With the ARC, I found a channel strip which is more than catching up my old unit. Impressively good preamp and a fantastic compressor always keeping your vocals perfect in the mix in a musical way - live or in the studio.
[Feb 2009 Germany]

Mladjan Milanovic

This box is awesome! I have no hesitation in recommending this unit, a world-class product!
[May 2006 Switzerland]

product review

Tape Op magazine by Craig Schumacher

What has 22 switches and 18 knobs, is accented with the colors of the rainbow, and is more flexible than a circus acrobat? Give up? The Buzz Audio ARC 1.1 Analog Recording Channel! It's a mic preamp, instrument DI, multiband EQ, and dynamics processor with opto compression and FET limiting-all in one 2U mono box. And the cool thing is, the four subcomponents can be used individually, or they can be chained together in any combination to form a complete recording channel. I don't have room to discuss all its features here, so I urge you to check out the manufacturer's website for extensive descriptions and images. My review unit came courtesy of Atlas Pro Audio.

The mic preamp is a natural sounding, Class-A, solid-state circuit that goes from +9 dB to +65 dB of gain. Input impedance can be varied from 220 ohms to 5500 ohms. And of course, there's phantom power. Next is the line input section, which has its own gain control and a switch to select the unbalanced 1/4'' front-panel instrument input or the balanced XLR line input on the back. The main output section that follows allows you to choose either the mic or line section and provides controls for output gain (with an additional 10 dB of gain), polarity reversal, clean vs. transformer output, and sidechain monitoring (for the dynamics section). A 13-element LED level meter on the far right of the unit can be assigned to show input or output level. The top most overload LED monitors the entire chain and will light if the signal exceeds +20 dBu in any of the ARC's subcomponents.

During our first test of the unit, we concentrated on the mic preamp and bypassed all the other subcomponents. The preamp sounded great and provided an uncolored and accurate picture. Nice and safe. But what about adding some color? Read on.

With so many features on the ARC, we decided to put it through its paces on vocal recording. We set up an AT4050 in cardioid and hooked that up to the ARC. I like the 4050 for the neutrality and smoothness of the mic. Great for vocals-especially for female voice and group harmony overdubs. The vocal track was a mid-tempo basic rock track that needed some close and up-front singing as the melody of the chorus was the hook of the song. The first thing we did was engage the "tranny" setting on the preamp. The manual states that the ARC's transformer is "designed to sound like transformers from the early years of audio and is made with a fairly low-grade steel core." Simply put, the more preamp drive you give it, the more harmonic distortion you get. By pushing the input to just below clipping, we got a nicely saturated sound, and the 4050 took on the characteristics of a tube mic. But the added harmonic distortion brought out more of the singer's sibilance than we wanted, so we started using the EQ and compressor to smooth that out.

The EQ has two parametric bands, both low and high shelves, and an adjustable high-pass filter. Each of these five EQ bands can be individually switched into the main signal path or into the sidechain of the compressor/limiter. By sending the high shelf to the sidechain, we were able to get the opto compressor to react more to high-freq energy, thus helping reduce the sibilance. We were barely into all the controls and already we were completely changing the sound of the mic and bending it to our will.

The ARC's opto compressor is adjustable with knobs for drive (threshold), ratio, and release time. Attack time can be switched slow, auto or fast (1 ms). You can place it pre or post-EQ, or as mentioned previously, it can be used standalone. The FET limiter, which follows the opto compressor, has a threshold knob and fast/med/slow release settings. Although there's only one set of rear I/O connectors for standalone (external) use of the dynamics section, if the compressor is switched to use standalone I/O, the limiter can still remain in the ARC's main signal path. Same goes for the compressor if the limiter is being used standalone. We found that the limiter was very useful in controlling the vocal dynamics, and we were able to adjust it to grab just the portions of the vocal we wanted without sounding overly compressed.

It's important to note here that the manual is well laid out and explains all the features of the ARC in detail. We definitely kept it around as the options on each section are extensive. With every section engaged, the ARC is more than a channel strip. It's a recording channel on steroids. The sonic possibilities are endless, and you can radically change any signal sent into it. The other great thing about the ARC is that you can use its various subcomponents for mixing. I used the mid-band parametric EQ and compressor on a trumpet track that was originally very pinched sounding, and I was able to really warm it up; the ARC really saved the track. (You can hear the results on the muted trumpet in the song "Burn That Broken Bed" on the Iron and Wine/Calexico EP entitled In the Reigns.) In my mind, this doubles the value of the ARC, as it's a serious problem solver for both tracking and mixing.

The ARC is clearly designed to be a useful and creative recording tool. Once you get a handle on the many ways of tweaking, routing, and switching, the ARC 1.1 quickly becomes an important part of your studio's setup. It's great for DAW users as well since it offers so many analog tools in one box. I wonder what version 1.2 will do?


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)

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.

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