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In Reply to: Regarding star wars, live music, and tube rolling posted by tubesforever on June 19, 2005 at 08:57:36:
On the 6DJ8 front, the only current production tube to consider (IMO) is the JJ E88CC. The JJ's sound is close to that of the W. European NOS that so MANY "inmates" favor. The JJ easily wins the price/performance battle, as W. European NOS 6DJ8 family tubes sell at very high prices.
Eli D.
Follow Ups:
You are right, Eli. Also my measurements indicate this as a matter of fact. My listening experience also conforms to this. However, I can bear a E88CC in a cascode stage, if so after all. It is constructed to reach up to 80MHz. That means that transconductance in relation to current is very high, but also the frame grid construction is not able to avoid a bad electron optics. This results in relatively high mu distortions. As the distance between plate and grid is small, the space charge is so, too. Therefore directly reflected electrons are not suppressed leading to a fine structure in the distortion pattern. Definetely not as high as in beam power tetrods, but still enough to be recognised as somewhat dark and back stage sounding.
If you do not need the low impedance of a E88CC cascode as the next stage does not have a high input capacity, a fine audio tube like 6 CG7 or the Chinese triple mica 12AU7 would be a better choice. In a first trial you could make a direct replacement of E88CC and 6CG7 because they are pin compatible.
Today I purchased some Amperex Buggle Boy 6DJ8 tubes and some Siemens 6DJ8 tubes to roll next. I am not sure about the Amperex but I hear the Siemens is very neutral and somewhat more linear than other brands. If I cannot get the sound I am after, then it is time to make sure my cartridge is loaded optimally.I am very intrigued about the 12AU7 tubes. 30% less power than the 12AX7. But I hear they may make a nice cascode preamp circuit. I have heard others comment about the 6CG7 as well. I do not know if this would require extensive reworking of my preamp or not....
I also purchased 4 12BZ7 tubes, GE Models. The seller says these are up to 30% more power than the 12AX7 so I may be willing to modify my circuit to get the higher gain. Then I can buy a low powered moving coil cartridge which is my future plan, and run it without a step up converter.
Here is the description of the 12BZ7's....
"From an audiophile's private collection, here is a remarkable NOS NIB matched QUAD of GE LONG CURVED BLACK PLATE 12BZ7 preamp and guitar amp tubes MADE IN USA in the 1950's or '60's. These are direct plug-in "big brother" replacements for the venerable 12AX7's. Three are labeled/boxed "GE" and the fourth is labeled/boxed "Zenith". It was actually made by GE (common practice back in the good old tube days). They have the SAME amplification factor (100), higher plate power dissipation ratings, can handle more power and therefore can be run at a lower percentage of their full capability which means their dynamic range is significantly better than 12AX7's in a similar circuit. My SAMS tube substitution handbook says that 12BZ7’s are great substitutes for 12AX7’s! All tested EXCELLENT on a TV-7B/U military tube tester."
I am hoping these will sound nice, if not, I will provide them to one of my Guitar playing buddies.....
They are not interchangeable with 12AX7- same mu, but half the rp, double the gm. Double the heater current, too. And much higher distortion, and high-order distortion it is.Give them to a guitarist- they don't belong in a hifi system.
"I am very intrigued about the 12AU7 tubes. 30% less power than the 12AX7."
The 12AU7 has got a maximum plate dissipation of 2.75Watts per section. A 12AX7 has got only 1Watt!
But I could only give a recomendation for the triple mica Chinese 12AU7. All others I know are not airy sounding.
Frank
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