Quote from the link I posted:
American designation 5AR4, European GZ34 are one and the same, and there is no proper substitute for this unique, indirectly heated cathode type-- the Mullard version is perhaps the best rectifier tube ever. Definitely do not sub 5R4, 5U4 or any filamentary cathode type; they produce DC almost immediately which could cause cathode stripping on your precious 300Bs (and any other tubes) Micronetics in Switzerland (Tubes@mnfoc.com)is a great supplier of this and many other scarce tubes. I e-mailed them yesterday; they have nearly a thousand (!) Mullards, as well as hundreds of Valvo and metal-base Philips GZ34. The Mullards are $65 per-- considering the alternative of paying $14 for a Sovtek which will never come close to the Mullard in performance and will last perhaps 20% as long as a Mullard, $65 is not too bad. Ebay is another source, as is Brent Jesse Recording online. His prices are great and he is a decent guy. Andy Bouwman of Vintage Tube Services (616)454-3467 may also have these, but his specialties are VT231/6SN7, 6922/7308, and ECC European series tubes. Hope this helps, Chris
You could also call any of the referenced tube suppliers. I have purchased from Andy Bouwman before and he is very knowledgeable. Good luck.
American designation 5AR4, European GZ34 are one and the same, and there is no proper substitute for this unique, indirectly heated cathode type-- the Mullard version is perhaps the best rectifier tube ever. Definitely do not sub 5R4, 5U4 or any filamentary cathode type; they produce DC almost immediately which could cause cathode stripping on your precious 300Bs (and any other tubes) Micronetics in Switzerland (Tubes@mnfoc.com)is a great supplier of this and many other scarce tubes. I e-mailed them yesterday; they have nearly a thousand (!) Mullards, as well as hundreds of Valvo and metal-base Philips GZ34. The Mullards are $65 per-- considering the alternative of paying $14 for a Sovtek which will never come close to the Mullard in performance and will last perhaps 20% as long as a Mullard, $65 is not too bad. Ebay is another source, as is Brent Jesse Recording online. His prices are great and he is a decent guy. Andy Bouwman of Vintage Tube Services (616)454-3467 may also have these, but his specialties are VT231/6SN7, 6922/7308, and ECC European series tubes. Hope this helps, Chris
You could also call any of the referenced tube suppliers. I have purchased from Andy Bouwman before and he is very knowledgeable. Good luck.
