The Pultec Mystique

 

Pultec EQs are highly-prized (read “expensive”) pieces of gear.  Software emulations are well- regarded as well.  What’s their secret to their allure?  Let’s find out.

 

by David Baer, Mar. 2015

 

We’re going to take a look at two EQs in this study, the Pultec EQP-1A and its frequent companion, the Pultec MEQ-5.  The hardware originals (or faithful recreations thereof) are still in demand today, a half century after they were first introduced.  Software emulations from a number of companies are also very popular.  Claims by respectable sources have been made that sound can be improved simply by passing signals through the units with no boost or attenuation dialed in.  This is said to be the case for both the hardware gear and software emulations.

What’s the secret of this magic?  I attempted to discover it and the report of those findings follows.

 

A Little History

The Pultec company was actually just two individuals, Ollie Summerland and Gene Shank.  They did everything: engineering design, production, marketing … the works.  They originally created an EQ that addressed a variety of boost and attenuation needs with an unsymmetrical set of controls.  This was the EQP-1, and it first appeared all the way back in 1951.  It was a passive unit, meaning it did its thing but signal level was sacrificed in the process.  A tube amplification stage was later added to restore the lost signal level, resulting in the EQP-1A.

Later a second model, the MEQ-5, appeared which was more focused on mid-band regions of the audio spectrum.  It had amplification from the start, so there was not a need for a MEQ-5A moniker.  Although the controls for the MEQ-5 are symmetrical, they are a little strange to those accustomed only to modern software EQ design.  We’ll get back to the panel layout in a bit.

It turns out that the two models made for very successful collaboration when paired.  This gear was also noted for superb build quality, one reason some of these units are still in service today (not to mention that they command a premium price when they come on the market).  Another reason for their popularity is the inspired passive circuit design, which allegedly produces very music-friendly audio spectrum alteration.  I say “allegedly” because I’ve never had my hands on a hardware unit, nor am I likely ever to do so.

In any case, with this background, it’s no surprise whatever that a number of major plug-in vendors took aim at creating emulations.  This list of companies includes Waves, UA, IK Multimedia, Softtube and Nomad Factory.  There are probably a fair number of home studio producers who have at least an EQP-1A emulation since it is part of the IK Multimedia T-Racks basic package (IKM does not offer an MEQ-5 emulation at this time).

The software we’re going to focus on here is the Nomad Factory Pulse-Tec EQ, primarily because it’s a plug-in that I own and also because it conveniently combines both the EQP-1A and MEQ-5 into one unit.  Nomad Factory took a little liberty with the hardware origins in that they included a third, separate amplifier component in the interface.  But the essential EQ-ing features of the originals are still there.

 

In Search of Vintage Fairy Dust

I happened to own the Pulse-Tec courtesy of a marvelous all-you-can-eat sale of Nomad Factory gear about three years ago.  I bought an everything-included bundle.  The Pulse-Tec being part of that bundle, the plug-in had been sitting on my DAW machine unused and unappreciated for quite some time.  But I would occasionally read very favorable posts about Pultec software in general and about the Nomad Factory implementation in particular which I filed away in the back of my mind.

Then one day I was trying to figure out a way to make a somewhat lifeless synth sound more interesting.  “Ah ha”, I thought, “maybe if I sprinkle some vintage fairy dust on it …”.  Now, I’m loath to admit that I really believe in such things, but hey, in the privacy of one’s own home studio, what’s the harm?  So I inserted an instance of the Pulse-Tec on the track.

My first reaction upon seeing the interface for the first time was probably not uncommon: “just what the hell is that thing???”. 


The controls on the EQP-1A (the middle component) are hardly what you’d call intuitive.  The MEQ-5 (the top component) is a little more reasonable in this department, but taken together the Pulse-Tec panel is not particularly user friendly.  We’ll come back to explaining how to drive this contraption in a moment, but let me finish this story first.

Not wishing to bail without at least giving it a listen, I opted to check out the presets, and found one called Master Mix Presence.  I called it up, and you know what?  It magically made the track sound better.  The effect wasn’t overwhelming, but there was a definite improvement.  Thus excited, I pulled up some other projects and tried the Pulse-Tec with this same preset.  In many cases (not all, but over half them) the result was a pleasant improvement.  Could I actually have found the mythical universal “goodifier” that blesses everything it touches with improved sound – and does so just using a standard preset at that?  Is vintage fairy dust real?  We’ll return for an answer later (but, spoiler alert, the answer sadly isn’t the one you’re probably wishing for).

But first things first … and the first order of business clearly is figuring out just what the knobs and switches on the interface do.

 

Introducing the Players

The less-intuitive of the EQ pair is the EQP-1A, so let’s get that one out of the way.  As can be seen in the image below, there are three areas of interest.  All the software emulations of the EQP-1A that I’ve seen follow this layout pretty faithfully, so if you’ve got a Pultec emulation other than the Nomad Factory, this still applies.

 

We have a low-frequency section that contains booth a boost and an attenuation control.  Those share the same frequency dial, which supplies five choices.  To the right, we have a mid-high to high frequency boost control with seven frequency settings and a bandwidth control (counter-clockwise yields higher Q).  This is the only Q control on either the EQP-1A or MEQ-5.  To the right once more we find a high frequency attenuation section with three frequency choices.

The most puzzling feature is undoubtedly the dual low-frequency boost and attenuation controls, but this is reportedly a feature that makes the EQP-1A appreciated by some sound engineers.  Both the boost and attenuation filters are of low-shelf variety.  But rather than canceling each other out, they can work in concert as follows.  The boost can add more dBs than the attenuation can reduce.  Furthermore, the attenuation frequency is higher than the boost frequency, so a bass increase with an adjacent reduction can be dialed in.  The images to the right show a boost/atten setting and the corresponding affect that has on white noise. 

 

While we’re examining this graph, note the pronounced high-cut roll-off starting at around 18.5 KHz.  I’m not sure what’s that all about, but it remains even if you disable both EQ sections in the Pulse-Tec and just leave the amplifier component enabled.  I double checked this against me IK Multimedia EQP-1A emulation and it was absent in the IKM unit.  It’s not clear why Nomad Factory chose to include this in their emulation, but I’m sure it’s not there by accident.

We can see that the mid-high to high boost and attenuation capabilities overlap, allowing a boost to the right of the attenuation in the frequency spectrum.  We’ll look at the actual behavior resulting from various settings for these controls momentarily.


The MEQ-5 control panel is much more immediately intuitive.  We have a peak, and dip and a peak, with respective frequency setting of five choices (mid-low), eleven choices (mid-low to mid-high) and five choices (mid-high).  Once again, the ranges overlap, so it becomes possible to place the dip to the left or right of one of the peaks.

OK, so now we know what the controls do.  The obvious next mystery is what the zero-to-ten dials actually accomplish.  Let’s take a look.

 

Taking the Pulse of the Pulse-Tec

One way to find this sort of thing out is to check out the spectrum resulting from running white noise through the plug-in, as was shown above.  But there is a vastly better solution if you have the Fab Filter Pro-Q 2 EQ handy.  The Pro-Q 2 has a brilliant feature that allows you to find a set of EQ settings that duplicate another spectrum.  By running a white noise signal through the Pulse-Tec, it was easy to find Pro-Q 2 settings that achieved the same result.

Let’s start with the EQP-1A.  Both the low boost and the low attenuation curves are of the shelf type.  Frequency-wise, the low-boost setting is close to what it says on the panel.  The attenuation is between two and three octaves above that.  Boost amount varies by frequency from a maximum (10 on the dial) of about 12.5 dB to about 16 dB.  In other words, this equipment would not be suitable for scientific control purposes due to the lack of consistency.

The high attenuation curve is said to also be of the shelf-type.  In my measurements, it was actually much closer to high-cut with a gentle 6 dB / octave slope.  Frequencies for high boost and high attenuation were a bit under what the panel setting promised.  Once again, no science stuff, please.  Finally, for the high boost bell-curve the amount of gain depends on the bandwidth setting, with narrowest bandwidth approaching 10 dB gain but only about 6dB for the widest bandwidth setting.

The MEQ-5 is a little easier to pin down, but once again, there should be no expectation of precision.  In general, each of the three bands occupies about two octaves of the audio spectrum.  In other words, as the gain or attenuation increases, so does the Q, and the bell shape stays about the same width at its base.  The two images to the right show a gain setting of 5 and then of 10 on the mid-high control.  As you can see, the bell is higher but is not appreciably wider with the higher gain setting.

The lower peak has a maximum (i.e., 10 on the dial) gain of around 10 dB, but that varies a little depending on the frequency.  The higher peak has a maximum setting of 7 to 8 dB, again depending upon frequency.  Finally, the mid attenuation maximum varies between 10.5 dB and 11.3 dB.

 

Characters Welcome

So, with this kind of lack of precision, why would any modern mixing practitioner opt for a Pultec emulation over a state-of-the-art plug-in like Pro-Q 2?  The Pultec is incapable of surgical removal of problem frequencies, which are a piece of cake with something like Pro-Q.  Yes, in the Pultec we have the quaint spectrum treatment of the lows with simultaneous boost and attenuation dialed in.  On the other hand, that too is easily done with a fully capable modern software EQ.

But then there’s the musical quality of the EQ, given that the simulation duplicates the analog behavior of the original hardware.  Well, that’s all very nice, but once again state-of-the-art digital technology can equal those music-friendly characteristics.  The Pro-Q 2 EQ has a mode called Natural Phase, which is new to version 2 and which is claimed to duplicate the phase alteration behavior of analog.  But Pro-Q can also be run in linear phase mode when needed.  Add to that the ability to dial in mid-side processing alongside normal stereo, all in the same instance.  A Pultec emulation can do none of those things.

So why would anyone in their right mind opt to use the Pultec over something more modern?  One conclusion I came to was that the Pultec EQs are, in fact, real characters themselves.  In using them, we have no visuals to guide us and there’s also the fact that each boost or attenuation band has its own unique behavior.  And that may actually be a very good thing in the end.  In using a Pultec emulation, we are forced to mix with our ears alone, something we should probably be doing in the first place.  The odd layout of the control panel is only a temporary deterrent.  Once learned, it becomes second nature to quickly achieve desired spectrum alterations.  In fact, since we must select a specific frequency setting from a limited number, it’s entirely reasonable that a more efficient workflow might be achieved.  No need to ponder minutia – just find something that sounds close to what you’re looking for from a few choices and get on with the job at hand.

So, while I’d never give up my precious Pro-Q 2, I’d be loath to forgo having the Pulse-Tec in my arsenal.  Having taken the time to learn the controls, I find it extremely easy to employ.  There’s a place for precision, high-function EQs.  But there’s also a place for “character” EQs, and the Pultec would be my top choice for character.

But what about the vintage fairy dust?  Some people on the computer music forums whose opinion I respect have opined that tracks can sound better just by running them through a Pultec emulation that has no equalization dialed in.  If that’s there, it’s either extremely subtle or my vintage ears aren’t up to the task.  I would be extremely interested to see the results of blind testing a group of audio engineers, however.  Is the vintage quality there or is the power of suggestion creating an expectation of improvement that’s self-fulfilling?  I honestly cannot say.

Ah, but let’s not forget about the Pulse-Tec’s Master Mix Presence preset (hereafter MMP for brevity), which can be seen in the full-panel image of the Pulse-Tec above.  I made the claim earlier that that delivered some magic, and I do believe it imparted a nice quality to a variety of material.  But a little deeper analysis reveals a possible cause.  The EQ settings in MMP are mild, a couple of dB at most, and the resultant overall level changes little, according to my DAW’s metering.

It’s common knowledge that “louder” usually leads us to discern “better”, and all mix practitioners need to guard against being led astray by this phenomenon.  But while the MMP preset didn’t raise the overall level significantly, check out what is shown by IK Multimedia’s T-Racks Metering plug-in.  One of the two meters displays shows a measurement of perceived loudness.  This takes into account more than overall level; it gives added weight to frequencies that our ears are most sensitive to.  The images to the right show the results of measuring white noise with the MMP preset first disabled and then enabled.  The “after” graph shows only a tiny increase in RMS level, but a more substantial increase in loudness.  The MMP preset primarily boosts that area of the audio spectrum known as “presence” which lies in the general area of 5 to 10 KHz.  This is also the general frequency neighborhood in which human hearing is most sensitive.

So, the DAW meters said “not much louder”, but the ears had a different reaction.  Mystery solved.

So, am I saying there’s no such thing as vintage fairy dust?  Absolutely not.  Even my old ears can hear the warming qualities of judicious amounts of tape simulation, for example.  But as to whether or not we find this in the Pultec emulations, I’m less certain.  However, I’m not asserting that it’s not there.  If you believe it’s there, that’s just fine.  If you don’t believe but want to, then maybe you could just clap your hands and it will be.  😀

 

 

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