The MEQ-5 Equalizer: History, Circuit Design, And Why You Need One

MEQ-5 Midrange Equalizer: A True Secret Weapon EQ

(We’ve previously covered a general overview and history of Pultec® EQs here as well.)

History of the MEQ-5 Equalizer

The Pultec® MEQ-5 was introduced in 1955, not long after the better known EQP-1A in 1953. It was designed by Pulse Techniques® co-founders and operators Eugene Shenk and Ollie Summerlin, originally intended to complement the EQP-1A circuit as a more precise tool for addressing the “power region” of music: the mid-range frequencies between 200hz-7khz where our ears are most sensitive.

Used in concert, the EQP-1A and MEQ-5 offered a highly musical solution for program material equalization across the entire frequency spectrum, with a great deal of control over the critical mid-range. And this combination is exactly how the two designs were meant to be used!

Talking Topology: Pultec® MEQ-5 vs. EQP-1A

One might assume the MEQ-5 and EQP-1A are nearly identical designs, other than the frequencies they target. At first glance, that wouldn’t be unreasonable: like the EQP-1A, the MEQ-5 is an all-tube passive EQ, using inductors with overlapping boost and cut frequencies for highly musical, broad-strokes EQ.

However, it differs from the EQP-1A in a few critical ways, which make it both an exceptional complement to that circuit as well as an amazing tool in its own right!

1. More Bands

The simplest way in which the MEQ design differs is that it provides three selectable frequency bands for equalization: two for boosting (labeled “PEAK”) and one for cutting (labeled DIP).

Despite having a similar number of controls, the EQP-1A is limited to just a low band (with separate boost/cut levels) and high band (with boost level and bandwidth control), plus a selectable LPF at 5,10, or 20k.

The MEQ-5’s three bands include a “PEAK” band for the low mids (200hz-1khz), a “DIP” band with 11 frequency options covering 200hz-7khz, and a second “PEAK” band covering 1.5khz-5khz.

This clever design opens up a wide number of configurations - far more than are available on the EQP-1A.

2. Fully Inductor-Based Design

Something even many dedicated Pultec enthusiasts don’t know is that the famous EQP-1A, often referred to as an inductor-based design, actually only has *one* inductor in the EQ path - just for the high band. This notoriously sweet-sounding EQ band is different in topology from the low boost/cut band best known for the famous “Pultec trick.” (More on that later....)

The MEQ, on the other hand, features dedicated inductors for each band. Three full bands of sweet inductor-based EQ!

3. What’s In An Amplifier?

There’s another critical difference in the design of the MEQ: the single-ended line amp.

Being passive designs, the line amplifier stage is critical for both the EQP and MEQ style circuits. This is where the significant insertion loss from a passive-style EQ is made up to make the circuit “zero loss” - not coincidentally, the exact characteristic that made the original EQP-1A in 1953 such a success over the Western Electric designs it was originally derived and licensed from.

Many assume that this portion of the circuit is repeated in both designs, but this could not be further from the truth!

While the line amp in the MEQ-5 shares 2 of its 3 tubes with the EQP-1A, that is where the similarities end. The push-pull design of the EQP-1A’s line amp is in some ways a compromise compared to the single-ended circuit in the MEQ, which naturally features more second-order harmonics and as such, a generally more musical character, especially flattering to the midrange.

Those who have heard the latter circuit in action could very well agree that it is one of the finest sounding line amps ever made, full of harmonic character, very musical with more even order harmonics being present. (One of the main reasons the MEQ-A was AudioScape’s second product was the direct result of building this line amp point to point and just hearing it by itself. You can utilize this amp section by itself on the MEQ-A/2A by simply clicking the bypass switch, as the line amp stage is always active, exactly like on the original vintage units.)

4. The “Pultec Trick” … x10

The EQP-1A is, of course, famous for the “Pultec Trick” on the low end - where the slight offset in frequency points and curves for the low frequency “boost” and “cut” controls creates a resonant bump when both controls are engaged.

What is much less often discussed is that the MEQ-5, with three independent and overlapping frequency bands available, is actually capable of a far greater number of “Pultec Tricks,” since each of the 5 frequency bands on the two separate “PEAK” controls is also available as a “DIP” option.

That means you can boost/cut 200hz, 300hz, 500hz, 1khz… and so forth, all the way up to 5khz, to create as many as 10 of these resonant boosts. Throw in the second “PEAK” band and you have a wild amount of possibilities!

Some FAQ’s about the MEQ circuit

Where does the MEQ shine?

We’ve often heard general statements here that say “mid-range heavy” instruments, but most instruments need some contouring in the mids. Yes, it can be magic on vocals, keys, horns and of course, guitars, but we encourage you to experiment, it works extremely well on any instrument or group. The high boost is more broad and musical (it doesn’t have the sharp option the EQP-1A has). For some, that may take more time to get used to. The broad boost on an MEQ-5 is very musical. Let’s be honest, if your high end needs dramatic sharp boosting, you probably need to go back, change the mic position and record again. But I digress…

Is the MEQ-5A a replacement for the EQP-1A, or vice versa?

These are two iconic equalizers for a reason. Much like an LA-2A and 1176 are complimentary but often used by themselves with exemplary results. These two eqs pair great together or can get the job done on their own.

So which one is right for you?

Start back with your setup and see which eq will best fit your setup needs. For instance, happy with your mixbus but need more sculpting on groups? The MEQ may just be the ticket! There’s a reason this is one of the most well known tube eqs, check it out for yourself!

You can check out our own MEQ-A recreation of the MEQ-5, and the new MEQ-2A here. (We also, of course, recommend the EQP-1A recreation EQP-A, and its stereo counterpart, the EQP-2A for the high and low ends of the spectrum!)

Wait, there’s more?

A short note on adapting the mid cut band from the MEQ-5 into the EQP-1A design.

Those who think shoehorning a mid band into the EQP-1A circuit is essentially the same thing are missing out on the excellent single-ended line amp unique to the MEQ-5, which is worth the price of admission alone! (There are, of course, other technical reasons to be skeptical of this two-in-one approach - we’ve covered it in depth before, but the short version is that compensating for an additional band pushes the EQP line amp beyond what it was designed for, causing bandwidth loss when that stage is inserted, not to mention everything else in the original design you will be missing out on, Eugene and Ollie knew best back in the 1950’s, and still do over eighty years later.)