Distopik EQP-1A

The Pultec EQP-1A was introduced in 1956 as a flagship product of Pulse Techniques (Pultec). At the time, Pultec was still a garage operation between two electrical engineers, who weren’t yet aware of the legacy they would leave behind. Audio engineer’s who haven’t heard of the name ‘Pultec’ simply do not exist.

The passive equaliser EQP-1A is an incredibly powerful tool. The way it adds weight and sheen to a source is unsurpassed, even though the device is very light on features. There are four bands of EQ, two boosting and two attenuating, with a rather confusing layout and naming. This often confuses the inexperienced modern-school audio engineers to the point that they don’t even bother trying to use the EQ. If that’s you, read along.

Its wide EQ curves, the particular frequency selection points, its tube-based output amplifier and transformers work in harmony to create a beautifully-sounding tool. As is characteristic of passive EQ designs, it is a broad strokes tone-shaping device rather than a surgical or corrective tool. The EQP-1A is capable of applying hefty boosts without sounding artificial and harsh, making it a stand-out for adding large amounts of air to vocals or huge bottom end to low-frequency sources.

Although the original manual specifically advises against this, engineers found that utilising both the boost and attenuation controls over the low band simultaneously yields a particular EQ shape that creates a powerful yet controlled bottom end, which is ideal for kick drums. The high-band can also be used in a similar way, using the attenuating filter with a high frequency setting and boosting the high peak at 10 kHz or 12 kHz. This can result in pulling back some harshness while restoring sheen and air.

In 2011, Pultec started offering once again a reissue of the EQP-1A, amongst other units, following over a decade of meticulous collaboration with the original designers. These modern units are not enhanced to leverage any modern technology, instead being faithful recreations equal to the original design. Many engineers run a signal through it with the EQ disengaged, just for the sound of the make up amplifier circuitry alone.

As the original Pultec EQP-1A is said to be something of a perfect storm of design and remains the benchmark for equalisation, we decided to feature a top-quality recreation in our system.

The Distopik EQP-1A represents our attempt on building a Pultec EQP-1A with as much of the original circuit as possible. We don’t like to waste space, that’s why our units are only 2U high.


  • 10-bit resolution on attenuation and boost controls


  • point-to-point wiring


  • ECC83 (12AX7)
  • ECC82 (12AU7) for Class AB make-up gain amplifier


  • Sowter 3603 (Input)
  • Sowter 9530 (Output)
  • Sowter 9330 (Interstage)
  • Sowter 9325 (Multi-tap inductor)


  • NOS Russian “paper-in-oil” capacitors

Recommended uses:

  • low-end heavy percussive tracks (kick drums, beats, …)
  • bass
  • vocals
  • mastering

Notable uses:

Player/Engineer Artist/Band Album Year Track Instrument
Tom Elmhirst Adele 21 2011 Rolling In The Deep Vocals


  • “The minute that the first unit showed up here, there hasn’t been a project that I have done here that there haven’t been all over on the mix bus, on individual elements, tracking… To blatantly, overtly name drop – we’re talking about everyone from Adele to certainly Katy Perry, Kid Cudi on The Hunger Games soundtrack, All-American Rejects, Pink... There’s never a moment where I think: ‘Oh, this is gonna sound better if we don’t use it.’” - Greg Wells


Rack1 MasteringTelefunken Tape


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mix:analog™ is a registered trademark of Distopik d.o.o., an audio technology R&D company based in Slovenia, European Union.

For business enquiries, please contact us at:

Distopik d.o.o.
Tobačna ulica 5
SI-1000 Ljubljana