BSM RPA Ritchie Blackmore's Preamp/Booster

For sale is my perfect looking and working BSM RPA booster. The image is of my pedal and not a stock photo.

These go for new 369$ new if you can find one.

No box or literature

The BSM RPA Special Booster is a combination of Ritchie Blackmore's AIWA reel-to-reel tape recorder preamp stage plus the high-pass treble booster function from Blackmores hot-rodded Marshal Major amp, to emulate Ritchies post ´74 sound with any standard amp. In 1974, right before the start of the "Burn" tour, Ritchie Blackmore changed his live setup. First and foremost, he wanted to play live with an echo effect and made the AIWA TP-1011 reel-to-reel tape recorder his first choice. This unit offered the typical 2/3 seconds echo repeat, perfectly matching Blackmore's natural beat. Additionally, Ritchie Blackmore used the integrated microphone pre-amp as a booster, and with this his beloved Hornby-Skewes treblebooster he used for many years was not longer needed and was sent into retirement. The necessary trebleboost function (from a technical point of view a "highpass" function), was built into his heavily modified Marshall Major 200 amp. The Major amp now received a cascaded pre-amp stage with a new, non-bridged cathode resistor at one of the triode stages to prevent to much overall gain. Additionally, the modified tonestack like on the Marshall 50 and 100 watt models, was triggered with a cathode follower. At the final stage, Blackmore´s Major amp was loaded with four pre-amp tubes (incl. the driver tube), instead of the factory stock three tubes. Further on, the 250Ohm screen-grid resistors of the four KT88 power tubes were changed to 1kOhm and the two 10uF electrolytic filter capacitors of the BIAS power supply were replaced by two 47uF (160volt minimum) caps. John "Dawk" Stillwell, Blackmore's tech, did several fine tunings over the years to Ritchie's Major amp, because Ritchie experimented with several pickups in his guitars as well as with several new ideas of his trademark sound.