Tungsol 5881's

The Ken Rad Black Glass and their various incarnations are all similar sonically but NOT the same. I have managed to collect about 30 primo versions of these tubes over the past six months. Of those I collected, I have found three primary signatures between them.

Fortunately it is easy to determine which versions you have based on the markings on the tubes. The three versions are, the 6SN7GT, the VT-231 and the NAVY.

I originally thought the NAVY version was a VT-231 since VT-231 is the designation for a militarized 6SN7 and the NAVY, last I checked, was a branch of the military... However... There are Ken Rad Black Glass tubes out there which are marked NAVY and have no mention of VT-231 but usually do say JAN-CKR-6SN7GT.

Like all Ken Rad Black Glass tubes, the NAVY version have a dark and mysterious air about them yet.... they do have more air than the others. Clearly, the NAVY version is more open and as a result, thinner throughout the midrange. The Bass is firm but doesn't seem to go as low as the others. Instead, the NAVY version rolls off nicely without trying to do more than it can.

The most natural of the heap would be the ones clearly labeled as VT-231. These also say JAN-CKR-6SN7GT in most cases. The highs are crisp yet distinctly less extended than the NAVY. This makes for easier listening - but not the ultimate - on brittle recordings, in highly reflective rooms or systems which lean toward being a bit bright. The mids have more heft and the bass does not seem to roll off at all yet at the lowest octave its not exactly snug sounding. More of a warm fuzzy at those levels. The mids though are very nice but do not even come close to the power body and weight of the standard 6SN7GT mids.

Midrange. This is where the standard 6SN7GT soars! I think its beautiful but those who focus on the highest of highs - air and transparency will no doubt be leaving the room. This tube can seem dark to those folks. Put this tube in a system which is reflective or bright and WHAM! you have air, weight, transparency, body, heft, slam and a natural texture that other tubes only dream of. Using this tube in a darker side of neutral type system or one with dampened room acoustics leaves you wanting something more open... then move up to the VT-231 or NAVY.

Hi bwhite, and thank you. Yea, I saw what you said about the KenRad black glass versions. I think mine are the "dark" ones. Admittedly, I like the sound that way sometimes. Although, perhaps, that's why I've ended up with the natural sweetness of the Tungol 6SN7 round plates. Let me know what you find out listening wise on the Rads.

Yea #2: I thought that the brown based Tung 5881's looked like mil-spec. With so many out there and war time production that makes sense - which is, of course, good for me! With C-Mas here they are a little high on ebay right now, but will snab a pair next January (also my Bordeaux futures "problem" has resurfaced...). Oh, I tried a coke bottle pair of Mullard 6L6's - thought they might be nice - but you've got it right: dull, compressed, no immediacy. That's why I haven't gone right out after the Tung 5881's.

Sylv. 5932's uh?

Hmmm.

Tungsol invented and introduced the 5881 and 6550. The Tungsol 5881 had a miconol base, sort of a tan brownish color. Transductance of each of these types was superior to anything made by competitors. Both types are beam power tubes. I am curious how the 5881s are being used in the Supratek circuit.

Describe the differences among the 3 types of KR Black Glass 6SN7GT please.

-Ed

Hey Mark,

The 5881's are clearly superior to the stock Sovetek's in the Supratek. Visually all the 5881's I've seen are very similar and are usually available on Ebay. Do a simple search for "5881" on Ebay...

I think all 5881's are "JAN" since 5881 designates it as a militarized 6L6.

Ordinary 6L6's and even something like the gray glass ST shaped Sylvania 6L6GA's sound dull and lifeless. Not worth the effort of seeking them out.

The Supratek will run without these regulator tubes in place. Its interesting to hear what it sounds like without the tubes vs with. This is a quick and easy way to hear what those Sovteks are doing.

Sylvania double black plate 5932's are rumored to be the "holy grail" for this application. I have been searching to find them but have had no luck.

Also you might be interested to know there are three Ken Rad 6SN7GT Black Glass versions out there, and each version has its own unique character. I've been meaning to post this to the Ken Rad thread but ever since I got into vinyl, I've had no time for this silly audiogon stuff!! :)