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Re: Thorsten's 300B taste test...

Hey Thorston,

Thanks for a very thorough reply to my questions last week. Your description of how you defined the rating scale seems reasonable. Someone else, or even yourself on a different day, may have developed a different scale, but that is not important. What is important is knowing what the basis was for the scale that you used. I know that I better understand your scoring scale now and have gained a better appreciation of the difference between the various valves.

I can relate to your discussion of the short wave radio, or other similar device, which you might consider a "zero." I was also far away from home when I experienced the virtues of news and music of the short wave radio, albiet for a different purpose (at least theoretically). I served in the Peace Corps in Africa for two years. Sometimes the ONLY link I had to my culture back here in the States was that little radio and I would listen to music (Casey Casim's top 40) and sometimes important sports programs (i.e., Superbowl) on the Armed Forces Radio. Believe me, that radio did sound like 100 when I was in the dire grips of culture shock and had no one with whom to speak English. However, what I considered important then (making any type of link to my past culture) and now are very different and the quality of the sound in the middle of Africa just did not matter (not really). Now, of course, it does, as I live through every day life, which can be boring in comparison, but my audio system does provide some color.

Your comment is interesting about how home audio at its best can sound relative to live music. You give home audio a score of 55 relative to live music. I have found that sometimes if the live music is amplified, that the amplification system can severely hamper the quality of live music. I presume what you are talking about is home audio relative to a live jazz band or orchestra which is not amplified and cannot be compromised. The home audio systems I have heard best is sourced by a turntable or digital, which at its best would be SACD. I have heard a turntable source sound very, very close to live (probably more like 75 percent), but I would have to hedge my bets there as I would have to hear the same music played live nearer to the same time frame as the home audio system. I have heard that master tapes are noticably better than either of those two source formats and should compete better with live music.

I do have a question on how you set up the testing. First I will make a distinction I have made and then follow it up by a question.

I have a set of JJs as well as the TJ Meshplates. When I compared the two sets of valves in my parafeed 300B amps using Hedlund Horns as speakers, the TJs were definitely smoother, but the JJs seemed to be slightly more dynamic. I recall that others made a similar finding. Then I saw a message by Brian Cherry in which he states that the bias for the Meshplates needs to be optimized. He layed out a matrix of voltage/current values for that line of tubes. Based on his matrix I adjusted the fixed bias current from around 60 - 65 to 80 ma (at 325 volts plate voltage). While the dynamics improved, the sound lost some of its warmth and become somewhat thin. I backed off the bias current to 70 ma and I realized a compromise in warmth of sound and dynamics. I have not gone back to compare the TJs to the JJs, but I can imagine that the TJs sound as good as the JJs with respect to dynamics, but still smoother from top to bottom. BTW, I am sure that I have the older JJs, not the newer ones.

My question: Did you attempt to optimize the bias current for each valve before your test (I know, I know, testing is difficult enough as it is without having to change bias every time)? Or did you select a single bias current at which you compared the various valves?

Thanks
Retsel


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