Bob's amps are a whole other world from the original Dynaco ST 70's. You have to remember that the originals are from the 60's or there abouts. They were designed to be simple and inexpensive, so compromises had to be used. They took many short cuts but the output transformers were the very good. Can't say the same about the power transformers, but they worked, just ran way too hot. I have restored or rebuilt hundreds of Dynaco amps and preamps and very few come into my shop working as they were designed. Many still work but don't meet most of the original specs. I have done conversions of the ST 70 with just about every board that has been designed for them. Bob's are extremely well thought out and executed. The only other one I have ever used that I think is worth using is Frank Van Alstine's update board. Frank has been modifying and updating Dyna stuff since the 70's and has shared most of the things he comes up with freely.