I find the best recordings come from plugging the source in directly to the R2R
Missing out numerous mechanical connections and unnecessary circuitry
As long as the source has a high enough line level a DAC or CD is ideal a phono stage or Tuner a bit lower but I can usually gaet a high enough level using the pots rather that the As CAL level +4dB
I did also calibrate one of my BR20s specifically for my Phono stage
Alan
Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, Micro Sieki MA505 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20, Revox A77, B77, PR99, TEAC X1000 & 3440, Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Avondale NCC300 Mono Block, Speakers Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500