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The Porter Grinder Prevision Mastering & Mix buss EQ

About the PG23

The PG was the first design I did exclusively under the GOLY moniker. Up until that point, I had been developing and offering designs for the DIY community for many years, and also building and analyzing most of the circuits floating around.

I had made quite a few units of Barry Porter's NetEQs as custom order projects, and essentially, the PG (Porter Grinder) was an deep dive into merging my experience doing those with the orginal Porter design, in order to create something which was not completely my own, but also, not just another clone. 

Porter NetEQ

One of my later NetEQ builds (2014)

Compared to the basic Porter circuit, the in- and output sections were completely redesigned, the shelving filters were redone, an MS section was added, and I rounded it off with a master gain control that basically works as a full frequency band.

A lot of hours were spent listening and  tweaking small portions of the circuit, and whole sessions were dedicated to listening to various opamps and comparing notes (more on that later). 


Matching capacitors for the PG


Frequency precision trims

Aside from working on just the sound and circuit, I also spent a great deal of time on mathcing the channels and making sure the EQ was enjoyable to work and interact with. 

Matching capacitors for channels does not mean that I match every capacitor to an absolute reference. They come in tolerances of 5 and 10%, which most manufacturers use as "good enough" in even high end botique designs. In the build process, I match caps for relative values, so the channel (L/R) are identical, and in addition to that, I use high tolerance detented controls, with an extra refinement in the form of an internal 25 turn trim-pot to add another level of precision

Listening session with Emil at ET Mastering

We spent a lot of time selecting the ICs for the parallel filter summing amps. For a long time, I was reluctant to reveal which one we used when asked (although, I did not succumb to dark strategy of filing off the part number) but at this point, I am almost proud to say, we uncovered a gem in the humble LM833.

It's not as esoteric as most of the choices we tried, so I was afraid some would extrapolate that the EQ would sound cheap, if they heard this is what we settled on. In the end, I do not make money manufacturing opamps, so while the part we selected is not glamrous, the process
 and work that went into selecting it definitely elevated the design.

At first, the PG might seem a bit too clean to be interesting, but give it some time. The parallel filter bus has a definitive sound to it, and this EQ does not fight you, which means you won’t feel any opposition when dialing in your EQ choices or tone. That can feel a bit "off" and a little invisible to even experienced engineers, because most of us are used approaching a new EQ in part by learning how to work around the artifacts when getting familiar with it

Do some tweaks,  make sure to bypass for comparsison, and you will hear it's personality shine through.

2 x 4 band EQ

Low/high bands switchable to shelving

MS capability

All stepped controls

€3390 ex VAT

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