The Porter-Grinder Precision Mastering EQ
The heritage of this EQ goes back to the Calrec console EQ designs, which were refined and developed by the late Barry Porter.
The files and schematics for Porter's "NetEQ" were available to the public, and after Barry's passing, it grew to be a popular build in DIY circles, with many additions and modifications.
Based on circuit boards offered by PCB Grinder, various renditions were built for (and by) mastering engineers, and it soon became a favoured tool, in its own right, and on par with the coveted Sontec and GML EQs.
The "Grinder" part?
In 2016, I had already built a few custom Porter EQs, and I started rethinking parts of the original circuit, based on the experience gathered.
To be completely honest, the original idea was to put out a scaled back, "less controls", but "easy-to-DIY" version as a kit, but rather than cutting corners, I got lost in the details at every step of the process.
So instead, it turned into a two year development and listening project, with numerous hours spent on circuit design and countless hours spent in front of speakers, with friends and colleagues.
What I have now feels like a very personal iteration of the circuit, with a new level of refinement. Still a Porter, but also, very much, a Grinder.
So what's new?
In essense, all thats been left untouched from the original Porter layout, is the parallel filtering section.
The In- and output sections have been completely reengineered, a Mid/Side matrix has been added, and the Q was changed to display even gain behaviour.
We also did extensive, blind listening tests, and even developed an opamp switching circuit to do so, before we settled on our choice of opamps. Not the most esoteric available, but in our opinion, the best for this circuit.
Porter-Grinder precision EQ
- 2 x 4 band equaliser
- 23 step Blore-Edwards switches for gain and Frequency control
- Channels are matched
- Six Q settings per mid band, 5 Q settings per low/high band
- Shelving mode on high and low bands (switchable on the Q)
- Gain of 0.5dB steps and a max of 5.5dB cut or boost per band
- LR/MS switchable interface
- Global bypass