Spectra Sonics

Spectra 1964 has offered the world’s finest hand-built audio equipment since 1964 and we still adhere to the same rigorous standards. Spectra 1964 is considered “vintage” now, but really it’s the forefront of modern recording technology!
Spectra 1964 was an integral part of many classic recordings. Their op-amps and EQs were utilized in the consoles of some of the most legendary studios in the world. Over the past 45+ years, their Model 610 compressor has found a devout following, including the likes of Tchad Blake, Dave Cobb, Vance Powell and many more.

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Model C610

Single-channel classic discrete compressor/limiter

The Model C610 is the based on the original 1969 version of the Model 610 Complimiter. From the custom anodized aluminum knobs and black trimmed vu meter, to the internal discrete circuits, the Model C610 represents what made Spectra an industry standard.

The C610 utilizes the same operation format as the original with the addition of a third switchable meter setting, as well as 80/240 50/60hz VAC operation. The hand-built modules are made and tested in the same manner as the original 1969 version. The quality of materials used in the processes of building the Model C610 remain the same as before. This build quality of all Spectra 1964 products is an important hallmark, which results in the long-term value of this unique technology.

50 years after its release, the Model C610 has specifications that go unrivaled in today’s industry, proving Spectra founder William G. Dilley was decades ahead of his time. And now, a new generation of engineers is discovering the Spectra sound for themselves.

Model V610

Single-channel mic pre and compressor with detented controls

A new concept in compression and limiting, that just happens to be decades old. In 1969, Spectra Sonics unveiled the Model 610 Complimiter, a revolutionary audio compressor and limiter.  At the heart of the Model 610 was the 601 Compressor/Limiter module.  This module allowed users to employ The Model 610’s compressor and limiter circuitry independently or simultaneously. Its low noise floor, ultra-fast peak limiting and intelligent compression earned the 610 its status as a classic studio compressor that is used by some of the best-known engineers in the industry. The Spectra Sonics Model V610 Complimiter can be considered an evolution of the original Model 610, utilizing the very same 601 module with updates to fit in 21st Century workflows that include tracking, mixing and mastering.

With amplifier stages based around the low-noise 110A amplifier circuit, the V610 is capable of 65dB of gain and +24dBu, making it a deft mic preamp in addition to its Complimiter functions.

Mastering applications

In mastering applications, the V610 has detented/switched controls for precise recall of all parameters.  The ultra-fast, fixed-timing peak limiter circuit operates fully within a 180 nanosecond range, transparently eliminating voltage transients without applying compression and effectively increasing the headroom of any device placed after the V610 in the signal chain.

The compressor circuit has a fixed attack around 100 nanoseconds, and variable release timing from 50 milliseconds to 10 seconds with full bandwidth at ratios from 1.1:1 up to 100:1, making it capable of both extremely transparent compression and hard compression.  For tracking and mixing, the V610 can be used to do anything from subtle, automatic gain control, to invisible peak limiting for safeguarding analog-to-digital converters, or to dial in aggressive, fast-release, compression to add color to your sonic palette.

Though the heart of the Model V610 was designed nearly 50 years ago, its brilliant design still has specifications that go unrivaled in today’s industry, proving Spectra Sonics founder William G. Dilley was decades ahead of his time.  And now, a new generation of engineers is discovering the Spectra Sonics sound for themselves.


“I’m hesitant to disclose to other mastering engineers what a wonderful game changer the V610 is.” – Garrett Haines

“They sound HUGE! I used the hell out of them on the new Jason Isbell record!!” – Dave Cobb

“The 610 has been my longtime ‘go to’ device for dirtying up drums, parallel compression, and other general ‘grit enhancement’ tasks. Its ability to pump and overdrive make it perfect for things like that. The 610’s not-so-dirty little secret is that, with proper settings, it can also be one of the cleanest, most transparent compressors available. Unique and invaluable. A classic.” – Pete Weiss

“They’ve been on every record I’ve engineered since, (1993), and most that I’ve mixed.” – Tchad Blake

“Behind me in the rack were mounted two 610 compressors that were a perfect fit across the stereo buss. How I missed that sound. Now, it’s back!” – Jack Douglas

Model 611

Single-channel classic discrete instrument and microphone compressor/limiter

Every once in a while, an idea comes along that just works. An idea that makes so much sense that it’s hard to understand why nobody else did it before. Enter the Spectra Sonics Model 611 Complimiter.

Spectra Sonics is known for their proprietary Complimiter circuit. The Spectra Sonics Complimiter circuit features the fastest analog peak-limiter in the world. For decades engineers have used this circuit to “invisibly” remove transient peaks from their tracks. Removing even inaudible transient peaks improves the headroom and performance of equipment downstream of the Complimiter. Now imagine applying this principal at the start of your recording chain BEFORE peaks can cause any performance issues.

The Spectra Sonics Model 611 Complimiter is a hand-built, discrete design utilizing custom transformer I/O that accepts a balanced line input, microphone input, or high-impedance ¼” input and is designed to be placed in FRONT of the mic preamp in your signal chain, thereby eliminating transient peaks as close to the source as possible. Removing peaks before the preamp allows the preamp to more accurately reproduce the source before the recording device.
Additionally, the compressor portion of the Model 611 Complimiter can be used to control the overall dynamic range – everything from evening out a bass track, to making a kick drum boom, or crushing a drum room mic. Plus, its small, portable extruded enclosure makes it easy to dial in sounds in the studio or control room alike. Perfect for producers and session musicians on the go.

Input pad

The 32 point, detent type input pad controls the amount of limiting, and/ or compression/limiting that is required. The pad allows for up to 30dB of attenuation.

Guitar/String Instrument Setup

The preserve dynamic range as well as optimum noise performance, it is strongly suggested that the guitar/instrument volume control knobs be set 50% or greater with consideration given to preserving sonic quality of the instrument signal output. By systematically adjusting the instrument output knob(s), and the input pad of the 611, the user will establish an optimum output between the instrument and the device.

Release Control

The release control knob affects the release time after initial signal compression. Maximum release time, marked “10” on the front panel, will slowly restore gain to the original level.

Slope Control

The slope control provides a wide range of compression/limiting ratios from 1.1:1, (linear amplification), to 100:1, or a flat slope. When the slope control is set for minimum compression, the knob is set at “10”, thus providing linear amplification of 20dB for input above threshold, (-46dBu).
When the slope control is set for maximum compression, the knob is set at “0”, for a flat slope.


A flashing threshold LED indicates transients, (peaks), at -46dBu. A constant threshold LED indicates program material.

Overload Indicator

The red LED indicates audio levels beyond -20dBu.

Gain reduction LED Meter

The gain reduction meter indicates compression, in dBu, relevant to input level and, or, slope setting.

  • Dramatic improvement in dynamic range and harmonic content
  • Reduced distortion due to the elimination of transient overload
  • Instantaneous control of dynamic range (compression function)
  • Unequaled Guitar/instrument sonic performance with either passive or active instruments pickups
  • No requirement for de-essing or high frequency equalization
  • Direct termination of microphones (phantom power required)

STX 100

500 Series version of the classic Spectra Sonics 101 amplifier circuit

The STX 100 is a 500 Series version of the classic Spectra Sonics 101 amplifier circuit. The STX 100 is a high-bandwidth microphone preamp with 64dB of gain and a 10Hz to 50KHz frequency response. A 10dB input pad and a dual potentiometer offers continuously variable input pad and output level controls allow the STX 100 to be used with both microphone and line level sources.

The STX 100 represents an affordable alternative for employing the same Spectra Sonics technology of our famous recording desks made over 40 years ago. The unique circuit topology of the STX 100 utilizes a 100 series discrete preamplifier design that was at the heart of every console built by the company. The result is unequaled performance in terms of expanded dynamic range, (headroom), low noise and distortion, as well as extended harmonic content of the amplified signal.

Most, if not all, conventional analog audio amplifiers live in a world whereby dynamic range limitations are dictated by audio program peaks. Audio program peaks, which can average 6dB to over 20dB, effectively reduce the undistorted output of a given amplifier by that peak to average ratio. The reduction in output limits headroom, (dynamic range), increases numerous forms of distortion, and limits the harmonic content of the amplified audio signal.

The STX series lives in the VU world, irrespective of peak to average transient audio program signal material. When a percussion instrument is the source, it is not uncommon to measure transient peaks that are 12dB-24dB above the program material average. Again, the STX series products are not affected by the high transient peak excursions. The first and second stages of the STX 100 utilize independent LED overload indicators to monitor program overload conditions. The result is faster set-up time with consistent and definable results. Drums sound like you are positioned next to them. Guitars have full harmonic content. The dynamic range of vocals is preserved.

  • Gain: 64dB
  • THD: Less than .01% @ 20Hz-20KHz
  • Signal/Noise: Better than 120dB, (unweighted)
  • Maximum Output: +18dBm, 20Hz–20KHz
  • Power Requirement: Less than 50mA, +18dBm
  • Input/Output Control: Continuously Variable/10dB Pad
  • Input Impedance: 5K Ohms, Nominal
  • Output Impedance: Less than 50 Ohms
  • Frequency Response: 10Hz-50KHz
  • Phantom: 48 Volts
  • Polarity: 180 Degrees/Reverse/Mic or Line Input

STX 500

500 Series version of the Model 500 2-band passive equalizer

The STX 500 is the rebirth of the Model 500 2-band passive equalizer. The STX 500 has four frequency selections per band and up to 12dB of boost/cut in 2dB increments. This passive EQ becomes the active feedback element of the STX 100 amplifier. Combined with the STX 100 there is zero insertion loss and introduces virtually zero distortion when boosting or cutting.

Each band also features an individual bypass. High frequency centers are 2.5KHz, 5KHz, 10KHz, and 15Khz. Low frequency centers are 50Hz, 100Hz, 200Hz, and 15KHz. Perfect curves evoke the feeling of classic recordings with every knob turn.

PLEASE NOTE: The STX 500 is designed to connect directly to the STX 100 preamp. The STX 500 has no VPR edge connector of its own to plug into an API-style rack. Therefore it cannot be used in a standalone configuration.