Thanks for the information! The only time I often see Westinghouse branded tubes is with the older elevated 6sn7gt to gtb and those tubes are nearly identical to the Marconi's made in their huge Montreal plant. I'm pretty certain Westinghouse had a tube plant in Hamilton Ontario, but who made what and who rebranded what, is really confusing. I suspect Westinghouse built the Marconi design under licence, but that's just a guess. Marconi held many early telegraph, radio and electronics patents, so they're almost certainly the patent holder. In fact Marconi USA was the foundation for what became RCA!

Hi Geoff043, I just received my Willsenton R8 a few days ago and love it. Question: are you using it as an integrated amp or a power amp with another preamp? How are the tubes working for you?

@@VintageLuxmanStereoCollector Hi Virgil Using it as an integrated. Enjoying this amp so much, my Musical Fidelity ms5i hasn't had a look in since. The Willsenton is such a bargain. Not sure if I will ever go back to solid states. Glad you are enjoying your new amp, it's a keeper.

@@MrShaggy789 - many thanks for your quick reply! The reason I contacted you was that I am using it as a power amp with an external preamp. Although I have ordered EL34 power tubes, does it make any sense to upgrade the preamp tubes (like you did) if I use a separate preamp. I have posted this question to a tube amplifier FB group since I am a “newbie” to tubes. Be well an continue to enjoy your R8.

@@VintageLuxmanStereoCollector I don't regret buying the input tubes Virgil, but the difference is not night and day. Ultimately, it's comes down to what you can afford. Performance difference for my ears is subtle. Good luck.

@@MrShaggy789 - I appreciate your candor. You saved me some money.

I've never found a definitive analysis of the codes. But in many cases you can use common sense and usually figure out what the year/month are, though often they don't make any sense.

If it has 6SN7 GTA inside a stop sign on the top of dome with a large chrome cap then it is almost certainly a Sylvania GTA. If on the other hand the label on top is inside a circle and the chrome dome just barely covers the top, then it's a Rogers/Sylvania, made in Toronto with Sylvania parts.

We've focused on the 1st cousin 6gu7 rather than the 6cg7, for the simple reason that there are too many manufacturers and variations of the 6cg7, and only 4 or 5 major ones for the 6gu7. And yes I like the Sylvania 6gu7, I actually like all 6gu7's, but the Sylvania has a wee bit more warmth in the mids. Like the 6cg7, the 6gu7 is nothing like a 6sn7 sonically. That is both good and bad, yes electrically all 3 tubes are very close and are interchangeable with adapters, but whereas the 6sn7 in general as a type has a lot of harmonic distortion, the 6gu7 has relatively low harmonic distortion and as a result a wee bit less warmth in the mids, but in exchange it has excellent clarity and detail. A worthy tube to roll in as a sub IMO (with appropriate adapters of course).

@@tubelab194 Thanks for your detailed reply. Any advice on neutral tubes for the nine pin freya noval would be appreciated

@@sopasadena1499 Charles has made up a large selection of Sets for the FREYA noval, just head over to the store and you'll find them easy enough. Charles even made up a filament current compatibility chart so you don't risk burning out the filament supply - the Link is in the listing.

Good question, due to space/time I didn't bring out every variation. However I should have definitely talked about my Sylvania Jan 12sn7's. The 12v heater version, absolutely rock solid, with a wonderful richness and a good level of detail. In fact that tube was what convinced me to build the prototype 6or12SN7 Preamp, which became the Universal 6or12SN7 Kit Preamp. I found a bunch of the JAN tubes all from1967 NOS NIB and have watched for more ever since - and I've never found even one!