Although I only have a MW 36.5 (single box) and a MW Sony 9100 and don't have a Transporter yet, I've been posting on this thread because - while there are threads on the two former pieces - this one has become the primary source of tube info on MW gear, which all have similarities in their output stages and power supplies.
This is an update (and a short re-cap for those who might be new and haven't yet gotten through all
37 pages of this fun journey
).
I've tried the following rectifiers in both the 36.5 and MW Sony 9100 (all NOS except for the Sovtek): Sovtek GZ34/5AR4 (stock tube), RCA 5U4GB, Tung Sol 5U4G, brown and black base Mullard GZ32, brown base Mullard GZ37, the High Wycombe GZ37, several different Mullard GZ34/5AR4s, an Amperex metal base GZ34/5AR4 and, recently, the EML 5U4G. I was able to try all but the Tung Sol, Amperex and EML in both pieces simultaneously and in all cases I found I didn't like using two of the same rectifiers (too limited and homogenized a sound).
The next result is that, for me, IMS, the best rectifier for the 36.5 is the GZ34/5AR4, primarily for it's tonal weight/density. The surprising part is that it is not the metal or fat base pieces I have but rather a regular black base Philips labelled Mullard from 1964 that is my favorite. This piece has the most even tonal and frequency balance and resolution of any of the more than half a dozen NOS GZ34s I've employed. Also interestingly, an early '60s regular black base Amperex labelled Mullard I have is
very close in sound to the Amperex metal base (extremely refined, and airy); while one of my two Matsushita (Japanese Mullard) units from the '70s has the fullest bass and is on the level of some of the '60s Mullards I've tried. All of this seems to confirm what Andy at Vintage Tube Service told me some time ago: that it is the quality of the individual (GZ34) tube that most matters, not the construction type or year of manufacture. This particularly makes sense when one remembers that tubes are hand made.
My favorite rectifier for the MW Sony 9100 has been the High Wycombe GZ37 for it's large soundstage, resolution, refinement and tonal accuracy. Followed by the black base Mullard GZ32 which excels in imaging and refined, extended, airy and dimensional vocals. I recently received the EML 5U4G and had it in for a week, in which time it became clear that it is at least on the same level as the HW GZ37, and perhaps better. I say perhaps because a very short while after I re-inserted the HW the transport on the Sony stopped working so I wasn't able to do an ABA comparison. But my impressions are that the EML piece combines most of the best qualities of the HW GZ37 with those of the black base GZ32; having the
relatively more forward (more pronounced leading edge transients) character and greater drive of the latter combined with the other above mentioned qualities of both tubes. I can see wanting to use the HW at times for it's slightly softer, more restrained quality but I can also see using the EML at least as often. It's fantastic that EML is making such a high quality tube, one that rivals the best of NOS.
Rob
