After achieving some very promising results with a NOS Type 8 8BB3C1B and my A-199 I have become interested in the challenge of installing a massive 17" 9AB3C1B reverb tank within my A100PMS12 and wish to ask for thoughts on adequate shielding. The toroidal transformers are emitting more pulse into my reverb tank than I thought would be possible, have spent a tedious hour with the whole thing under power, carefully sliding the tank around inside looking for neutral positions. I can tell you all that when the A-199 return signal isn't having to fight electromagnetic interference, it sounds bloody marvellous and clean. Add a compressor and you're in BBC radiophonic heaven. I omitted the RCA connectors and have hard soldered Belden shielded wire from A-199 PCB to reverb tank input and output transducers. Belden wire shield connected to ground on A-199 pcb. Have located the mu-metal product 3M Ultraperm 80, however I don't know if the rejection and permeability are correct for blocking PMS12 transformer hum just a few cm away. Cheers!