Yorkshire based Graham Slee has been in touch to tell us that his invention has received its long awaited United States Patent and explains what it is used for. 

The technology is used in both the company’s Accession phono stages: the original one for MM, MI and HOMC cartridges, and the Accession MC.

What this invention does according to Graham is “address most objections to active EQ done in the high gain (and therefore “hard working”) amplification stage” adding “It does it by recognising that the typical RIAA replay curve seen in text book illustrations and all over the Internet, is not of the record’s doing. It seems unimaginable to think that a magnetic cartridge does not have a flat output, but it is the cartridge’s fault that the replay response rises at 6dB per octave”.

Image supplied by Graham Slee


He explains “The mid frequency step you see is the record’s contribution, as well as some low frequency boost from 50Hz, otherwise the record’s response would be flat. Even the patent examiners had trouble understanding, and that’s the problem when misinformation becomes so deeply rooted. It took 4 years for the US patent to be granted, but the idea stems from research I started 40 years before. Back then this solution could not be implemented. It is only since the introduction of the op-amp, and a specific genre of op-amp, that this type of EQ became possible. If my career had not included a stint in broadcast audio design I could have missed this particular genre of op-amp. It’s so good for music and the perfect fit for this type of cartridge EQ. So there it is. One could say it’s been my life’s work. I know it took up a good part of it! Today it’s here for you to enjoy your music from vinyl.”

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