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The problem with the MW TP is that its too addictive - I work from home and take the odd break which can stretch into an extended listening session.
Hi guys, it has come to my attention that at least a couple of you have experienced blown fuses when using the GZ32 rectifier tube with the Transporter. We confirmed the same here, depending on the tube. I have reviewed the datasheet and confirmed the reason. We are using a cap-input filter with the Transporter, rather than a choke input type. All of the preamps and outboard supplies for the player mods use a choke-inpu filter.If the first thing that the rectifier sees is a capacitor at its output, there is a large inrush current as the rectifier tube charges the capacitor. The larger the capacitor, the larger the inrush current. We are using a pair of 100uf-450V caps in series from B+ to ground, resulting in a net 50uf capacitor as load to the rectifier. The GZ32 recommends a max 60uf cap, but that is dependant of the resistance of the coil windings and input resistor value. The GZ34 and 5U4 have similar recommended limitations, but they perform flawlessly. As a result, I would simply recommend AGAINST the use of the GZ32/5V4 tubes in the Transporter.The only thing that may happen, if the GZ32 rectifier is used, is that the 3A SB fuse may blow and need to be replaced. This does not in any way damage the unit or tube, but does require removal of the lid of the Transporter to access 3A SB fuse on the mod tube board. It is a 5x20mm size fuse.Thanks,Dan W.
Phil,Be patient and you will find a tested metal base GZ34. Dan snagged his GZ34 recently as a 'Buy it Now' for less than $150 and I have found 7 for under $200. Search E-Bay Germany for the Volvo (Philips production) or E-Bay Netherlands. The Philips, Mullard, Miniwatt and Valvo branded GZ34 are are Philips production and the same tube. As these were made in Holland, you can find some pretty sweet deals if you search these sites.Good luck!
Everyone's ears are different of course, but I'll be presumptious anyway and say that I think the DR's are the holy grail of signal tubes for the MW TP.As for the Mullard GZ34, until you've heard a metal base, don't give up on that model. I realize they aren't cheap, nor available on every street corner, but WELL worth the effort. The difference between the regular black base and the metal, are night and day. Completely different sonic presentation. The former: syrupy, rolled at both extremes, wonderful midrange, good but not great soundstage and depth. The latter: fast, detailed, extended at both extremes, soundstage is wide and as deep as the ocean, depth is as it should be. It is one of those perfect combinations that allows instruments to float in their own little space, with perfect layering, and yet oodles of weight to every one of those instruments within that stage.As I mentioned to ted in a PM, I'm done with my tube rolling.YMMV
As the DR's start to 'dry up' then we need to find the next best thing (or better) for future TP owners - Parts Connexion are selling cryoed versions of the 'newer' 6H30, could this be the answer? Also the 6N1P is a good cheap tube, maybe this could be cryoed for further improvement? I'm happy to send a few tubes off for freezing - anyone have any recommendations for cryoing companies?
I replaced a fat base Mullard GZ34 last night with my latest Tung Sol 5U4G. After about an hour of warm up I settled in for what I can describe as the best sound yet (with my Bent TAP preamp; the 36.5 front end isn't due back till Wednesday). It has a sound that is both deep and wide, yet with nice dynamics and detail. Very nice so far. Of course the signal tubes are the DR's.I've run my Philips Mullard (June 1966) GZ32 with no problems. It's one of my faves.