Tube Characterization: 6dj8, 6922, 7308, E188CC

Thanks Hartwerger.

Joe's Tube Lore is really what stimulated my interest in tube characterization. In a way, you might consider it a classic.

In a vain effort to expand on that knowledge base I proposed an across the board characteriztion of this family of tubes and their sonic attributes. This was met with quite a bit of opposition and defense of Joe. The information I gained however was invaluable.

I suppose that I need to sharpen my communication skills as this new post was intended to steer clear of objective analysis (believe me I don't want to go down that road again) and focus more on the individuals perception of what good sound is.

Perhaps I will repost like this. "Why do you like tubes?" or "What do you like about tubes"

In my ARC preamp I tried stock ARC supplied Sovtek tubes, then Upscale Audio EH6922 Platinum Grade and currently have Amperex made for Mullard in Holland(late 1960s).

Sovtek are a bit sterile sounding, a bit harsh on top.
But overall this was not as bad of a tube as some people describe it to be.

EH tubes are better than Sovtek with better bass, fuller midrange and with just a bit smoother highs. I think these tubes may work better if I listened mostly to classical music. EH tubes tend to sound a bit forward on some rock music recordings.

The Amperex/Mullard tubes beat both the Sovtek and EH. Highs are silky smooth. Midrange is full and vibrant. Bass is deep, powerfull, textured and well controlled. Soundstage is wider and deeper. Excellent tube overall for basically any type of music.

I think if my system was a lot more laid back in nature, then possibly the EH tubes could sound much better. But in my case, these 1960s Amperex/Mullard tubes are just a better choice.

Overall I am pretty happy with how my preamp responded to different tubes. Sometime in the future I plan to give NOS Amperex 7308 a try. See how it compares to my current tubes

I have recently installed Amperex 7308 tubes based on the review in Vacuum Tube Valley issue 9 and this is what I found:

The bass is really excellent and well defined all the way down to what seems like the limit of my speakers (von schweikert VR4Jrs @ 23 Hz). The bass and mid-bass are tight and well controlled and the character and timbre of the instruments in this range are very realistic and musical. The midrange is somewhat liquid and I guess you could say palpable. The high end is sweet end extended and actually has some weight. It's a really great tube. I purchased the U.S. made pulled from military equipment, but they spec'd really well so I went for them. It seems that I have seen these with gold on the inside of the tube, but I don't know what this signifies or what effect it has on the sound. Overall a very lucid, musical tube with a consistency of sound quality (consonance)top to bottom.

My next foray will be with the early Phillips Miniwatt and the Seimens 7308 circa 1961 if I can find them for the right price. I've heard the Siemens vary greatly between early and late manufacture and I wonder if the Phillips do too.but Older just seems to sound better across the board.