Using the Pultec Eq on a Drum Beat
You've laid down an epic drum beat. You have made sure to marry the right sounds together, nailed the timing and feel of the beat and now comes the fairy dust. Colouring and gluing the drum elements in the beat to afford a single homogeneous sound is not as difficult as it first seems. The tools we have available nowadays are incredibly powerful and process specific. I love single function processors that do one thing but do it well and software manufacturers have noted the fact that we can now string a bunch of plugins together without worrying about taxing our CPU resources. But even with all these wonderful tools that are available to everyone I still end up using Old School techniques and processors and when it comes to low end management or anything that needs to have the low frequencies defined I use vintage equalisers and notably the delicious Pultec EQ.
There is a reason we use the Pultec topology to process low frequency content.....read on.
When we talk of vintage equalisers we are invariably talking about analogue topologies. Whereas digital equalisers are used for surgical tasks vintage equalisers are used to add colour and fairy dust to your sounds. Linear phase topologies lend themselves well to precision equalisation tasks but it is the minimum phase topology that adds colour and in abundance!
Analogue EQs are governed by the circuit path and components used in the hardware. The imperfections of this system allows for phase shifts, harmonic distortion and added noise, and it is these types of anomalies that, when designed well, can come across as 'musical'.
We now have digital equalisers that emulate vintage designs. How well they can emulate the randomness of the hardware equivalents comes down to coding. Filter curves and phase shifts are emulated to the point whereby some manufacturers offer a plethora of various filter types within the same equaliser. The advantages of the digital emulator is that it is reliable, accurate, recallable and multi instances of it can be used within the DAW without breaking the bank!
But there is more to vintage equalisers than the circuit path and components used. Some vintage equalisers have specific filter curves that distinguish them over other models.
The original Pulse Techniques Inc (known as Pultec) Model EQP1A equaliser, introduced in 1951, is so popular that many manufacturers have copied the topology and offered them in software form. The original passive design suffered from the usual mismatched input to output gains and therefore they integrated an amplifier stage (denoted by the A in EQP1A) after the equaliser to restore unity gain but even with this amplifier stage the output was only boosted by 20dB.
In recent years we have had many reincarnations of the Pultec EQ design and although there might be variances from manufacturer to manufacturer the one things that has stayed constant is the behaviour of the filters. The low and high frequency bands have both boosts and cuts and at the same selected fixed frequency. However, they are not reciprocal in that the cut and boost differ ever so slightly. The result is a complex yet musical EQ. The interesting behaviour of of this topology can be seen graphically and when you look at the resultant response you will be amazed. As an example: if you boost and cut (attenuate) at 100 Hz you will see a scoop above the cut-off frequency. If you boost and cut at 10 kHz you will see a scoop just below the cut-off frequency. This translates across, in a mix context, as both clarity and focus. In usual eq designs a boost will simply boost the frequency range selected but with a vintage design and specifically the Pultec topology cuts are placed either after or before the cut-off and this highlights the cut-off even further. This topology is extremely powerful when it comes to low frequency management.
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