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Historically, AZ4 was parts of a new generation rectifier tubes, following up the famous RGN Series of Telefunken, intended for applications the AZ1 by Philips, could not do. AZ4 is in between 274B and 5U4G.
The smaller AZ1 was the mostly used rectifier tube in Europe, and electrical identical to RGN1064. The more powerful AZ4 is on par with stronger tubes like RGN2004.
AZ4 is an ideal candidate for HiFi applications. It can easily supply a stereo amplifier using a pair of AD1 or 2A3, as done for instance in the Yamamoto A06-03 amplifier.
The base of this tube is an original old Bakelite base, that we remove from NOS tubes
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