Supratek Tubes and Tube Swappin' for Everybody

Aloha Fiddler! Thanks for the invitation - It would be great to meet you and see your show but unfortunately, we've got all our activities booked out and will be unable to get to Maui on this trip. Perhaps next time - which may be in the next few months....my wife wants to move here.

Whoopadeedoo - as a tube dealer, I am surprised you don't know that especially with military spec tubes, printing means something. And yes. There are three distinct "flavors" of Ken Rad Black Glass tubes. In vintage non-military spec tubes, parts & materials can vary tremendously. Differences in tubes are audible even by month of manufacturer in some cases.

What kind of a Supratek do you have?

Whoopadeedoo - Are your Visseaux 6L6G's the ST glass or tall skinny glass? I got quite a few of the latter but I've only seen picturers of the former. I rolled them in my Sauvignon a long time ago. I used Sylvania 5932 dual plate for about 18 months. First in the Sauvignon and then in the Cabernet. It is IMO a real sleeper as regulator. I think the unique dual plate structure is what sets it apart. It gave me a rock-solid soundstage with neutral freq
response. Regulator tubes are a different lot when it comes to judging sound. Some of the regulator substitutes have an unusually high heater current and will place a larger demand on the power supply and also affect the current draw through the rectifier hence the voltage sag on the recifier and ultimately the operating point on the signal tubes. I wonder sometimes if that load is adversely affecting the expression of the music or maybe it's just getting everything in its sweet spot.

Sylvania VT-231 has excellent top-end extension, tight bass but could be lean for some tastes. Sylvania 6SN7GT 1952 tall boys are very similar to Sylvania VT-231 but with a bass boost below 100hz. RCA grey glass have maybe the best midrange of all 6SN7GT's with very nice harmonics.

Hi Jazzdude,

I have both the carbon coated ST Visseaux and the tall GT glass version. I prefer the GTs by a small margin. If you want to sell any of your GT Visseaux, I'd love to buy them :-)

Tung Sol round plates stays in my 6SN7 position the vast majority of the time. However, I love the RCA grey glass midrange when I'm looking for something a bit more romantic and full. I'll swap in the Sylvania VT-231 or Bad Boys if I want more air.

-Len

Hi Bwhite,

You've arrived at the erroneous conclusion that base prints mean something. They don't. It was not uncommon for base prints to be labelled months after the actual date of production, sometimes completely removed from the actual site of production (e.g. at distribution centers, where a lot of rebranding occurred). With the two notable exceptions of 5692 and W/WGT-suffixed tubes, there was no such thing as as a military-designed 6SN7 .... only different base prints for military-designATED 6SN7 (the US military used VT-231 as its numbering system, the British used CV1988, etc.). Yes, these tubes had to be made to milspec standards, but no, they weren't any different then their commercial-bound counterparts. There wasn't a factory churning out just military-designated tubes. Factories distributed the same exact tubes with different prints based on its intended destination. A Tung Sol 6SN7GT in commercial red and blue boxes is the exact same tube as a Tung Sol VT-231 in tan military boxes.

What are the three "flavors" of Ken Rad black glass you speak of? I've removed the glass from about half a dozen Ken Rads with various base prints (fwiw: I'd be happy to post pics of the internal constructions of some 6SN7s). Perhaps you've stumbled across some insight I overlooked. The only differences I've found is minor mica variations and grid posts constructed of different materials.

It's logical fallacy to assume that the differences you hear in tubes is due to vintage or material differences. Each and every 40s tube was hand-assembled by both skilled and not-so-skilled laymen. Thus, they're subject to variations due to build quality alone. Chances are, any differneces you heard were quality control related more then anything else.

To clarify, I am not doubting you hear differences. Some people simply have better auditory acuity. But you are the first person I know who can hear marked differences in Ken Rad black glass 6SN7/VT-231.

I currently use a Chardonnay.