[kilohertz]

Hi all,


I am finally getting around to play with my RM5 and realized this is at least 40 years old and probably overdue for an overhaul. I saw somewhere that some versions didn't use the cathode bypass caps and wondering if anyone knew why or what versions did or didn't? Going to update the PS caps as well. One other thing I noticed, Roger put all the heaters in series, I haven't measured the voltage across each yet but couldn't that leave an unbalanced condition, ie one tube 6.5v and another 6.1 etc.?


Look forward to hearing from those of you who have experience with this fine preamp.


Cheers

[Kcin]

Roger liked to do this with heaters- he did it on a direct drive amp I commissioned from him. Perhaps it was also his practical side, maybe he had 12v transformers in stock or got them cheap and he series connected a pair of tubes, who knows?

The difference is( was) that Roger would measure heater and  operating current in the supplied tubes so he would match them.

Good luck with that today. Although, you could set that type of experiment up most hobbyists won't. Good testing tubes are not necessarily equal in current draw.

[lafish54]

You might reach out to Scott Frankland [https://scottfrankland.com/] who was one of Roger’s authorized techs back in the day, and a fine preamp/Amp Designer in his own right. He’s also involved with the folks in Santa Barbara who are working on bringing back Music Reference. And he’s a nice guy, has worked on a number of my pieces over the years, including my Rm200MK2.