RCM Audio might not be the first name you reach for when it comes to up-scale phono stages. The company is a small six-man affair out of Katowice, in Poland. When not making phonostages, RCM’s other job is a Polish high-end importer with brands like SME and Dynavector in its arsenal, so perhaps its resolutely turntable-related product line (just three products, two of which are phono stages alongside an integrated valve amplifier) makes sense.
RCM Audio’s best-known product up to this time was the Sensor Prelude IC, a two box IC based MM/MC phono stage with passive RIAA equalisation, in two drab boxes. This sub-£2,000 phono preamp is the kind of giant killer that many have compared favourably to practically every phono stage irrespective of price, and has a habit of turning reviewers into owners in minutes. It was so good in fact that it was hard to see how to better it, unless you are in the habit of referencing things by their size and thickness of front panel. The nearest thing to criticism of the RCM (prosaic nature of the cases aside) was that it had relatively limited cartridge loading options, especially compared to top-flight stages from Pass and Burmester.
This created something of a conundrum for RCM Audio. The Sensor Prelude IC was almost too cheap for today’s high-end buyers, but getting significantly better performance from what is one of today’s best phono stages was proving difficult. However, learning from the Sensor Prelude IC allowed the company to come up with THERIAA. In fact, the THERIAA could be summed up as a dual mono, high-specification version of the Sensor, but without the small value decoupling capacitors dotted around the circuit.
It is still a two box IC-based MM/MC phono stage with passive RIAA equalisation, in two boxes, albeit ‘drab’ is replaced with ‘well-built, but functional’. But the sophistication of the adjustable gain and loading (this time using expensive Omron DIP switches) and an expensive laundry list of highspec components from Elna, Nichicon, Vishay and more has helped bring the linearity to the RIAA curve from an already deeply impressive ±0.3dB to a remarkable ±0.1dB across the 20Hz-20kHz range.