modification on Revox PR99

I did this mod before the Studer A810, Revox PR99 is a semi pro machine, look same as B77 ( I don't know this model well ) but different in out look. PR99 not too expansive in E bay, but most of them is NAB only no CCIR, for play back Tape Project's tape is very easy just change two resistor's value will do R21 to 3.3K ,R54 to 680K, this good for CCIR 15ips, of cause a selector switch is needed for back to NAB. most of the hi end tape deck in there golden age is 99% transistor electronic circuit, transistor is less heat less power supply low voltage low noise low cost etc. but in the circuit needs too many coupling cap,use one for in put and one for out put in every stage, at that time people did not pay attention to the cap's sound quality, not like to-day's supper cap will cost more than $1000/pcs compare to less than $1/pcs in the same value of capacitance, there are 6 coupling cap per channel in the repro amp and more in the out-put amp, they all aluminum electrolytic type, very small in size, but big in capacitance, the only modern cap with big capacitance but not in electrolytic type is Solen fast cap, but size huge, no room for them in the original PCB, so I gave up all the record amp and oscillator PCB for room and make the machine for play back only. also by passed the out put amp and volume control, directly from the repro amp in RCA out-put. all hook up wire changed to silver. I had two PR99,only modified one , in show and tell night, friends want judge by themselves with no mark on the two machines, but end up playtime for the original one was less than a minute for the whole night clearness is completely different
tony ma