Just finished and tested this preamp with 5687 tubes. One input only, two outputs for bi-amplification convenience. I used two transformers, whatever I had at hand. One for high voltage, 250 volts with RCRC filtration. One for DC regulated power supply for filaments. Sounds great, however, in direct comparison with octal Aikido with 6SN7 tubes, I prefer octal. This one goes to ebay. Here are some pics.