LRno©

No cap sounds as good as no cap
Engineering genius Stephie Bench had the brilliant idea of using only inductances and resistances but no capacitors to accomplish the RIAA-EQ in her phono stage aptly named "LRnoC".

When I heard her design preparing for ETF.04, I knew she was up to someting big. So when she sent me a pair of PCBs and when Sowter offered the necessary iron (two interstage and two output transformers plus four additional chokes) as a package, I just had to bite… I've modified the original circuit slightly by using two grid leak chokes from Lundahl instead of a resistor–highly recommended!–and by adding an MC-step-up transformer from Jensen. The RF leaking in was easily cured by winding some copper tape around the cores. I spent a lot of money for custom wound toroid power transformers with electrostatic screens which in hindsight was not necessary. It pays out to use Pearl's shock-absorbing tube sockets since those D3a are can be quite microphonic…

To my tin ears, this phono stage is one of the best I've ever heard. In direct comparison with conventional designs the influence of capacitor coloration becomes rapidly (and glaringly) apparent. The "LRnoC" sounds very open, neutral, fast and uncolored. A highly recommended design and quite easy to build even w/o PCBs.

Links:
Stephie Bench's great site


Download: lr_no_c_rev_3.0.pdf