A dozen precision variations on “analog,” all in one EQ.



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

• thEQblue12: $389
• thEQblue6: $239
• Upgrade from thEQblue6 to thEQblue12: $189


Yes, Your Blueness

Why develop yet one more parametric equalizer (PEQ) when there’s already hundreds on the market? The answer is simple…’Cuz there was room for improvement! 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. Over several years, our Dr. Christoph closely analyzed many of the best out there, and compiled a vast knowledgebase of analog EQ best practices. Cherry picking from that, he implemented not just one or two, but an entire collection of trad minimal phase EQs. The result? A distillation of analog antecedents, while others are based on new ideas. We know you’ll enjoy our dozen variations of blue, newly revised by MAAT, and find your favorite sound.

The Twelve

We wanted to lift analog to another level, so we reverse engineered a variety of well respected hardware EQs, creating idealized digital versions from that inspiration. Rather than models or simulations that carry analog baggage, thEQblue has no noise, distortion or other secondary effects inherited from analog.

thEQblue is the most complete collection of classic equalizer architectures ever assembled into one package. You get precise, idealized examples of legendary analog equalizer circuitry, complemented by progressive new models. Whether it’s vintage, modern, or experimental, thEQblue is a sonic sandbox for every mixing and mastering engineer to play in.


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 perfected 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 audio engineer in the quest for perfect sound. As Spidey (and Voltaire) always reminds us though, “With great power comes great responsibility.” When designed by a clueless or cost–constrained software engineer, it can be your greatest sonic enemy.

Choice Is Good

In order to give you a choice of features and price, thEQblue is available in two versions:

  • thEQblue6,  with 6 architectures; №s 1 through 6 below
  • thEQblue12, with 12 architectures; all twelve below
☞ thEQblue6 owners can upgrade to get all twelve architectures.

Type Comments & Analog Kinfolk
01 ../assets/images/products/thEQblue/FilterCurves/01-Classic-SymmetricCROP-87bcfd3f.jpg Classic Sym Series symmetrical, almost constant Q bell — common mix desk & outboard gear architecture, try on “surgical” applications
02 ../assets/images/products/thEQblue/FilterCurves/02-Classic-AsymCROP-4e58dc51.jpg Classic Asym Series asymmetrical — Old Skool, boost like № 1 but with narrower cut
03 ../assets/images/products/thEQblue/FilterCurves/03-Proportional-1CROP-3803d5c7.jpg Proportional 1 Series proportional — More musical than constant Q, especially for mixing and post. Bells are wider at <6dB and narrower at >6dB
04 ../assets/images/products/thEQblue/FilterCurves/04-Proportional-2CROP-af87727d.jpg Proportional 2 Series proportional — Like № 3 but with bigger changes at large gain settings > ±6dB, try on vocals
05 ../assets/images/products/thEQblue/FilterCurves/05-Proportional-3CROP-e39f74d8.jpg Proportional 3 Series proportional — Like № 3 but with extra wide bells at small gain settings, from 0 to 3dB
06 ../assets/images/products/thEQblue/FilterCurves/06-Const-Q-AsymCROP-ffd05b83.jpg Const-Q Asym Series asymmetrical, constant Q — Boost like № 1, cut like № 5 (extra wide), as found in some USA products & mixers
07 ../assets/images/products/thEQblue/FilterCurves/07-Const-Q-RCROP-0c891a3c.jpg Const-Q Asy R Series asymmetrical, constant Q — Like № 6 but with mirrored boost & cut
08 ../assets/images/products/thEQblue/FilterCurves/08-Const-Q-InversCROP-ed8bd8d6.jpg Const-Q Invers Series symmetrical, constant Q — Similar to № 7
09 ../assets/images/products/thEQblue/FilterCurves/09-Const-Q-IdealCROP-6b53279b.jpg Const-Q New Series proportional, constant Q — Our special architectural style…try it!
10 ../assets/images/products/thEQblue/FilterCurves/10-Const-Q-NewCROP-b4693988.jpg Const-Q Ideal Series ideal & constant Q — Another special, similar to № 1, all three parameters (resonant ƒ, gain & Q) are independent, no analog relatives!
11 ../assets/images/products/thEQblue/FilterCurves/11-Parallel-FF-FBCROP-c74b373a.jpg Parallel FF-FB Parallel feed forward/feedback — Complementary amplitude and phase characteristics for boost & cut (symmetrical), found in high end graphic EQs, 1st choice for mastering [reference Massenburg]
12 ../assets/images/products/thEQblue/FilterCurves/12-Parallel-LC-AsymCROP-df17eee5.jpg Parallel LC Parallel passive LC — Tonal advantages with band interaction & asymmetry disadvantages, found in old or newly recreated PEQs, another choice for mastering [reference Massive Passive, Sontec]

Constant Q is more for surgical applications, while proportional EQs are best when combining multiple overlapping Sections. As a point of reference, API, Pultec, Masselec and Avalon EQs are all of the proportional type.

Note that all 12 architectures are normalized to have exactly the same bell shape at 6.02dB of boost. This allows you to easily compare the sound of each architecture.


Better By Design

thEQblue is built on the belief that exceptional fidelity, enhanced workflows and less visual fatigue are hallmarks of better quality toolsets. Our reliance on hard science and focused research balanced by in–depth listening and customer feedback, redefines audio tools for you and your fellow hardcore media professionals worldwide.

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
  • Up to twelve PEQ styles for every job: classic, vintage, modern and unconventional
  • Different Q characteristics: classic, constant–Q, proportional, ideal–Q and special
  • True high resolution emulation of analog equalizers, not modeling: no added noise, distortion or other non–linearities
  • Support for up to 384 kHz sample rate, suitable for HRA and game 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
  • Twelve 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 slopes
  • Very low noise and distortion upsampling for analog–like filters at baseband sample rates
  • 80 bit 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, each with different PEQ architectures, can be opened simultaneously
  • Stereo/Left–only/Right–only/Mono/Diff mode for each Section for all Serial types
  • Band grouping function lets you simultaneously alter ƒ, Q and gain for multiple Sections
  • Six fMODES quantize the resonant ƒ setting of all Sections, including Massive Passive & Maselec
  • Keyboard button enables you to target frequencies by ear then lock them to a Section with a click
  • Tunable Keyboard so that the sonogram aligns with material’s tuning
  • ƒ lock function when you’ve found your resonant frequency and want to alter just Q or gain
  • True Peak metering alerts you to TP overs
  • Sort button rearranges Sections in order, from low to high, with a single click
With a very wide range of choices, you are ready to tackle any job with a subtle or obvious approach.
  • Tracking, mixing & mastering
  • HRA post including ultrasonic tailoring
  • Broadcast production & post
  • Game production
  • Reinforcement: microphone response improvement, speaker deficiencies correction, acoustic compensation
  • Sound design & enhancement
  • Restoration & correction of transmission losses

Iron Maiden

The contribution of distortion to the specific sound of a particular analog equalizer caused by its respective electronics is largely what makes it “good.” Usually though, non–linear distortion, horrific group delay and other deficiencies produce more “nasty” than “magic.” Our philosophy, for PEQ design, has always been to make filters as precise and clean as possible. For controlled distortion, we recommend high quality tape emulation, a well made pedal or other carefully applied studio magic.


With thEQblue, you can simultaneously call up twelve Sections from one of the twelve architectural styles available. For each Section, choose from nine freely assignable filter topologies, including bell, first and second order low or high shelf along with first and second order low or high cut. The most significant filter types bearing the equalizer name are bells or peaking filters. Set to a particular Q, different bells change their bandwidth depending on the amount of boost or cut making comparison difficult between architectures.

How to Compare Architectures…

In order to make meaningful comparisons of different architectures you must be aware of two factors:
1. All 12 equalizer architectures are normalized to have exactly the same bell shape for 6dB of boost. If you use just one bell filter at +6dB, you will get the same audible result for all types. This normalization of the Q or Quality Factor is a unique MAAT feature, and distinguishes our typologies from their analog antecedents because many of the originals have undefined Q definitions due to the limitation of analog technology. The normalization allows you to compare the different EQ architectures in thEQblue with ease.
2. A single minimal phase bell filter with identical shape will sound the same regardless of architecture. The difference between styles becomes obvious when you have activated more bells and other filters so that they start to interact with each other. This will reveal the different characteristics of each architecture, in terms of phase interaction and different gain and Q relationships.


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 bandwidth 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 series implementation, filters are cascaded; each fed from the output of the previous filter. Unlike a series 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 style 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 series 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 architecture 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 architectures can provide 1st and 2nd order cuts. The 2nd order filters have a Q adjustment to create a resonant filter response, and can be combined to provide very steep “brickwall” slopes 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.

MAAT Minimum Phase EQ Plug–Ins

Feature Comparison

thEQblue6 thEQblue12 SantaCruzEQ6 SantaCruzEQ12
Features     ⊹ Notes ⊹
Architectures§ Twelve architectures: №s 1-10, serial type; №s 11-12, parallel type 6 total; №s 1-6 12 total; №s 1-12 6 total; №s 1-6 12 total; №s 1-12
Sections Five topologies available: 1st & 2nd order, variable slope cut & shelf; parametric bell 12 total; all five topologies 12 total; all five topologies 6 total; #1 & 6 are cut & shelf only; #2 - 5, all five topologies 6 total; #1 & 6 are cut & shelf only; #2 - 5, all five topologies
Metering Signal present + wide range & numeric TP Signal present + wide range & numeric TP Signal present Signal present
Panorama Control Left–only, R–only, mono, stereo, L-R Yes Yes No (stereo–only) No (stereo–only)
Spectrogram Yes; can be disabled Yes; can be disabled No No
Tuning Yes; ƒ–snapping Yes; ƒ–snapping No No
Upgrades Yes; thEQblue12 for additional cost No No No

§ – For more on the architectures incorporated into thEQblue and SantaCruzEQ, see our Understanding EQ Architectures PDF.

‡ – Parallel architectures do not support L-R Panorama mode.

Reviews & Testimonials

Michael, Romanowski, Coast Mastering

“MAAT’s thEQblue is a remarkable EQ plugin. The interface is unique among the multitude of EQ plugins available. Showing a different kind of representation of energy as it is distributed across the frequency spectrum. I like that the information is very customizable, depending on needs or particular projects. More impressive to me is the number and types of slope profiles available. I find them all very usable for different circumstances. I don’t have a “go to” slope, as each project is different, and requires listening before making any decision.
What I like most about the thEQblue is the sound. As a mastering engineer who chooses to work in the analog domain, all of my adjustments are Out-of-the-Box with analog hardware. For me, this has always had the feel and presentation that I am looking for in my work for my clients. However, the thEQblue is the first plug-in I have used that actually feels like an analog piece of hardware. When I make an adjustment with the thEQblue, I get the sense of turning knobs on my outboard gear. The way that the gain and slope react has a very known, comfortable feel to it.
This is not a transparent EQ. If that’s what you desire, MAAT’s thEQorange will greatly impress. thEQblue’s subtle to more apparent tonal color, for me, represents the best of a very powerful and adjustable analog EQ, in a digital platform. Very well done MAAT! I dig it, and would highly recommend it to anyone who may struggle with the use of plugins where they were wanting to use hardware before.”

Stephan Mathieu, Schwebung Mastering

“thEQorange became my unrivaled critical EQ from day one on, period. Now that I’ve added thEQblue to my strictly selected palette of ITB processors, I can say that I’ve found my absolute dream team. So very well done, and I can’t wait for your version of the LP SplitComp to arrive, which most likely means that I’ll be able do all my ITB work with those three products. Maximal minimalism, my dream for 25 years coming true.
You know, the last 3 days I found the time to really deal with blue, and yesterday I started to become really excited with the MAAT EQ team. Not like having found a new toy, but having found a solution. I’m working all day with plugins since ’96 and something I’ve learned quickly is that I don’t want to use most of them but try to master only a handful instead. Here I go, and thanks again for that…Keep up the brilliant work.”

Sean Diggins, Digital Diggo Mastering

“thEQblue is a sleek, blue-sky clean “curve machine.” It's always about the curves and blue has the lot.”

Arpad Tchiba, engineer for award–winning classical pianist Martin Tchiba

“…Excellent, overwhelming! and looks beautiful. Thanks very much. It was absolutely worth waiting for.”

thEQblue actually improves on the original Classic PEQ Blue, with increased precision for even finer low amplitude detail, as does SantaCruzEQ since it uses the same algorithms.
Bob Olhsson (Gearslutz) on the original Classic PEQ Blue

“I still use blue and red…Blue and red remain unsurpassed sound-wise.”

TKFP (Gearslutz) on the original Classic PEQ Blue

“You know mixing without blue, is like cereals without milk. So many good and usable EQs out there. Lets face it. Im a sucker for that good EQ tho. I really rely on it. I dont wanna see my new system running without it. That Algo stuff is still untouched. Its really good. Really good.”

Reviewers & Engineers! Want to add your voiceover to the mix?

Head to our Contact page and give a shout…We’d love to hear what you think!

Speeds & Feeds

Features, Specifications & Downloads


• Download the user manual for thEQblue here

• Download Understanding EQ Architectures for thEQblue here

• If you own thEQblue or want to demo, grab an installer of the current build…
Installer — For macOS
Installer — For Windows


  • Fully parametric minimum phase EQ
  • Up to twelve unique idealized architectures, derived from analog circuits
  • Panorama control targets left–only, right–only, mono–only, L-R–only, or stereo
  • Optional live spectrogram
  • AutoGain for effortless A/B comparisons
  • Variable resonant ƒ tunings for common Western scales
  • Inbuilt tone generator for quick spectral navigation


  • AAX (Pro Tools 10.3.10 and newer), AU, VST 2, VST 3
  • Sample rates from 44.1 to 384 kHz


VST PlugIn Interface Technology by Steinberg Media Technologies GmbH


  • Perpetual: One–Time Buyout…
  •    thEQblue6 — Architectures 1-6
  •    thEQblue12 — Architectures 1-12


Order thEQblue Now

• thEQblue12: $389
• thEQblue6: $239
• Upgrade from thEQblue6 to thEQblue12: $189