A few years ago I had the chance to buy a very nice amplifier from a friend’s friend. An amplifier built by Alex Ederer, an Austrian tube amp builder, who is famous for his excellent choice of special tubes putting them together in interesting circuits. The amplifier was equipped with fantastic old German directly heated tubes. The Telefunken RES964 as a power tube, the RE084 as a driver and a RGN1064 as a rectifier. It was a single ended amplifier and the RES964 was running in triode mode. This was my first single ended amplifier and beside that I although never listened to those ancient tubes, I felt that the circuit was giving something really magic to me, as if I experience my record collection completely new. The RES964 is not the most powerful output tube (nominal output is below 1W), but in combination with my high efficiency speakers from Oleg Rullit, there was never a lack of too low volume.

After a while, maybe this is human nature, it was in my interest to make further experiments with this amplifier. There is nothing easier than tube rolling. Luckily I found out that the tubes I used were in ‘mass production’ in the mid 1940s, resulting in many tube derivates from other manufacturers than Telefunken. Just to name a few, there are equivalents for the RE084, like the Valvo A408, Tungsram LD410 and the Philips A415. For the RES964, there are Valvo L496D, Philips E443H and the Tungsram PP4101. The list of RGN1064 derivates and different designs is nearly endless, giving me the possibility to try out many things.

During this period I got in touch with Antonello, while I was searching for special tubes. Antonello is a fantastic source for tubes, very often having these strange things I never saw before! I got this wonderful RE084 derivate from Marconi from him the R.A. 408/14.  In original packaging. To repeat myself: Really wonderful!

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