A dozen shades of analog, all in one EQ.

thEQ Blue


Beautiful analog colors, twelve in all, that will take your work out of the ordinary.

Coming Soon…Price: $590

The Twelve

The most complete collection of classic equalizers ever in one package. You get precise emulation of legendary analog equalizers, complemented by progressive new models. Whether it’s vintage, modern, or experimental, thEQblue is a sonic sandbox for every recording and mixing engineer to play in.

Yes, Your Blueness

Why develop yet one more parametric equalizer (PEQ) when there’s already hundreds on the market? The answer is simple…’Cuz we can do it better! It was customers of the original LinearPhase PEQ Red and Orange who asked Algorithmix to develop a classic EQ, for recording and mixing tasks, with unparalleled purity and transparency. Our Dr. Christoph started by closely analyzed many of the best out there, and decided to implement not just one or two, but an entire collection of trad minimal phase EQs. The result? Most of them emulate analog antecedents, while others are based on new ideas. We know you’ll enjoy our newly revised dozen shades of blue, and find your favorite sound.


The equalizer is perhaps the oldest and the most popular of sound processing tools. From its earliest days, the main function was correction or enhancement by boosting or cutting certain frequencies.
For a century, engineers have developed countless equalizers. A few became legend, our thEQorange is one. The most popular version in recording and post is the parametric equalizer or PEQ, first described by Massenburg in 1972. It offers maximum flexibility with only three controls. Properly used, the PEQ is a powerful tool and the best friend of every sound engineer in the quest for perfect sound. As Spidey (and Voltaire) always remind us though, “With great power comes great responsibility.” In the wrong hands or, worse still, designed by a clueless or cost–constrained engineer, it can be your greatest enemy.

The Good, The Bad & The Ugly

Nowadays, hundreds of software paramets are available. Many of them claim to be The Best EQ…Ever. The truth is, few of them are recognized as worth more than the 10 minutes it took to download them. You may ask, “Hey Grandpa, why does one equalizer sound great while another sounds like !‡ı◊#??” This question, almost as old as Grandpa himself, still isn’t completely settled but we do have our own secret sauce. On one hand, there are some obvious rules which must be followed when designing a good sounding PEQ. On the other, some more esoteric claims have never really been proven. Treasured analog examples are considered by some as being both unique and unmatched for attitude by any digital EQ. The truth is that with a properly designed, fully parametric PEQ, every amplitude and phase characteristic of any other equalizer can be recreated.

Iron Maiden

Of course, the contribution of distortion to the specific sound of a particular analog equalizer caused by its respective electronics has to be considered. If the distortion is “good,” it may make some material sound better. Usually though, non–linear distortion, horrific group delay and other deficiencies like limited dynamic range produce more “nasty” than “magic.” Our philosophy in PEQ design, has always been to make the filters as precise and clean as possible. For controlled generation of distortion, if you do need any, we recommend using high quality tape emulation, a well made pedal or other carefully applied tricks.

thEQblue borrows the innovative code from Algorithmix’s original PEQ Blue, and wraps it in a modern, higher fidelity environment designed to help you be more productive.
  • The most complete collection of classic analog equalizer emulations
  • One dozen different equalizer types: 10 serial & 2 parallel
  • 12 PEQ styles for every job: classic, vintage, modern and unconventional
  • Different frequency characteristics: classic, constant–Q, proportional, ideal–Q and special
  • True emulation of analog parallel feedback equalizers
  • Support for up to 384 kHz sample rate, suitable for high resolution DSD and DXD production and post
  • Extended center frequency up to 80 kHz for filtering and correction in the ultrasonic
  • Bell filters in all PEQ types are normalized to look identically at +6 dB of gain and Q of 0.71, ideal for quick comparisons between types
  • 12 sections with 5 freely assignable parametric filter variants: bell, low shelf, high shelf, low cut and high cut
  • Extremely low noise and low nonlinear distortion algorithms result in residual THD+N significantly lower than 24 bit quantization noise
  • Adjustable Q Factor for shelving and cut filters
  • Multiple low and high cut filters can be overlapped to achieve brickwall characteristics
  • Very low noise and distortion upsampling for analog–like filters at baseband sample rates
  • 80 bit double precision internals virtually eliminate rounding errors
  • Resizable and zoomable frequency response rendering for precise adjustments
  • Parameter editing via numerical fields or directly on the Graph
  • Presets for quick setup comparison
  • Several instances, with different PEQ type selection, can be opened simultaneously
With a wide range and shades of color, you are ready to tackle any job with velvet or iron.
  • Tracking, mixing & mastering
  • HRA post including ultrasonic tailoring
  • Broadcast production & post
  • Reinforcement: microphone response improvement, speaker deficiencies correction, acoustic compensation
  • Sound design & enhancement
  • Restoration & correction of transmission losses

True Blue

After we unveiled our modern take on linear phase equalizers, the best mastering engineers heralded their unparalleled clarity and transparency. To develop a classic PEQ for recording and mixing, we knew that no single style could satisfy all the different flavors and genres passing through your desk. Intensive R&D followed by careful attention to UX, the user experience, resulted in thEQblue, a parametric equalizer with twelve different aspects. It contains the most complete collection of classic, vintage, modern and experimental equalizers ever in one plug–in. We know you’ll find your favorite flavors for each application and obstacle. To avoid any hassle with trademark, we haven’t assigned any brand names to each type. Being the geeks that we are, we instead gave each of them nondescript names related to their technical classification. You are invited to discover the sonic nuances of each one, and assign your own corresponding brands and/or products.

The Most Comprehensive…Ever

With thEQblue, you can call up twelve Sections, each one from the twelve flavors available. For each Section, choose five freely assignable parametric filter types, including bell, low or high shelf, and low or high cut. The most significant filters determining the equalizer name are bells. Set to a certain Q, different bell filters change their bandwidth in a specific way depending on the amount of boost or cut. To allow practical comparison between different equalizer types in the Classic PEQ Blue, the bells in all PEQs have been normalized to 6 dB of boost, i.e., a separate bell looks identical for 6 dB boost and the same Q, independent of chosen PEQ type.

Classics All

The Classic Symmetrical is the most popular bell shape used in many mixers and outboard equalizers. It is almost “constant Q.” That is, as resonant frequency changes, the Q or Quality Factor changes, widening as the frequency goes from low to high to maintain a constant ratio of center frequency divided by bandwidth. Constant Q is roughly the way our hearing perceives an EQ’s effect.

The three Proportional PEQs emulate bell characteristics which change their bandwidth proportional to their boost or cut. Many think they behave more musically as you don’t have to correct the Q after every amplitude change. There are also three other constant–Q equalizers available, with characteristics similar to some classic American brands.

thEQblue also offers two proprietary constant–Q varieties. The first, Constant-Q Ideal, is a perfect version of the Classic Symmetrical equalizer, having exactly the same bandwidth at any amplitude within its range of Q. This is measured 3 dB below maximum amplitude at and above +6 dB of boost. Such PEQs are impossible to implement in the analog domain, hence the “ideal” name. Another specialty variety is the Constant-Q New, which follows a new Q definition. It preserves exactly the same bandwidth at the half of the maximum amplitude for all amplitude values. Unlike the classic Q definition, this includes the range below 6 dB of boost. Due to its amplitude/bandwidth dependency in terms of a classic Q definition, this new kind of constant-Q PEQ could also be thought of as a member of the proportional group.

Finally we emulated two vintage parallel equalizers. With parallel construction, the main input feeds every filter in parallel, with each filter’s output being summed together for the final composite output. With a serial implementation, filters are cascaded; each fed from the output of the previous filter. Unlike a serial parametric equalizer (almost all paramets are serial), parallel–connected filters combine or cascade differently. They also behave differently in terms of phase. Their special interactive behavior between bands is offset by a pleasing sonic character. Our Parallel LC emulates old skool parallel passive PEQ circuitry built with inductors and capacitors. The Parallel Feed–Forward/Feedback topology emulates the feed–forward/feed–back designs still popular in low noise analog graphic EQs. While the feed–forward path is trivial to implement, the feedback path is impossible to implement in traditional digital signal processing, because of the need for so called “delay–free” feedback loops. In thEQblue, we apply a unique and very elaborate technique for true emulation of delay-free feedback. The result is a characteristic sound and perfectly complementary filters for boost and cut.

The Filter Library

In thEQblue, not only are various bell–shaped filters available but also different kinds of shelving filters. Nine of the serial equalizers use a special shelving design characterized by a cut–off frequency defined in the middle of the transition region. We found these filter definitions more intuitive than the classical “–3 dB below maximum.” The old skool definition is only used in the Classic Asymmetrical flavor in order to conform to its analog antecedent. All 2nd order shelving filters have a Q adjustment to emulate vintage characteristics, with their inherent and specific bumps at higher slopes. Also, the parallel equalizers are equipped with respective shelving filters shapes that are typical of old parallel PEQs. They also have interacting bands as did their analog predecessors.
Every complex PEQ is equipped with cut filters. With thEQblue, each of the twelve equalizer flavors can provide 1st and 2nd order cut filters. The 2nd order filters have a Q adjustment to create resonant filter response, and can be combined to provide very steep “brickwall” filters by cascading several Sections.

Best of Both Worlds

thEQblue is a creative equalizer tool combining the best of both the analog and digital domains. To avoid bell filter asymmetry at high frequencies for baseband sample rates, typical of many digital equalizers, we have applied reference–quality upsampling, which automatically kicks in for 44.1 or 48 kHz. By using proprietary filter algorithms, we have achieved a huge dynamic range, as well as extremely low noise and distortion. This yields unparalleled sonic purity, impossible for any analog circuitry.

Speeds & Feeds

Features & Specifications


A broad palette of colors and attitudes to suit every occasion.


AAX (Pro Tools 10.3.10 and newer), AU, VST2/3 M/W
Sample rates from 44.1 to 384 kHz




macOS 10.8 and newer / Windows 7 and newer, 32 & 64 bit


Coming Soon…Price: $590