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In Reply to: RE: Low plate resistance vs. reputation for 'good tone". posted by Iczerman on November 16, 2010 at 11:15:45
It's interesting to read that all the below, whom I respect, do at least like the ECC99, as I do. I currently use an ECC99 as a CCS for a 6SN7-based driver, but I have been thinking of constructing an Allen Wright SLCF, using all ECC99s, (for CCS, for driver, and for constant voltage source). I had some hesitation to replace the 6SN7 in the role of driver, because that tube has always been a great favorite of mine, but the slightly lower output Z and higher current afforded by the ECC99 makes it tempting. I use cascoded ECC99s as CCSs in my Atma-sphere preamp, too.
Follow Ups:
I love the 6sn7. Used it for a line stage, the second stage in my phono preamp and as a driver for the 300b.
Now I don't have a single stage that uses the 6sn7.
A autoformer volume control did away with my line stage.
I use a 7119 for the last stage of the phono preamp as it has a lower output impedance and slightly more gain.
The 300b sounds better to me with a 5687 driving it. Miller capacitance is harder to drive than some people understand. 80fp of capacitance will have a reactance of only 20k ohms at 100kHz.
The 5687 CCS loaded driver stage has a output impedance of about 2k ohms while the 6sn7 is 7.7k ohms. 2k driving 20k is much better than 7.7k driving 20k.
Remember, if we can't have 100kHz unadulterated then we won't get 10kHz right. Yes I know that the output transformer won't get 100kHz right but that's not license to give up the fight. These things make audible differences.
P.S. It is a little weird having all these great 6sn7's I've collected and cherished over the years and now I have no place to use them in my system.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
The 'Miller' capacitance of a 2A3 is higher than that of a 300B - 93 pF versus 82 pF. That of a 45 is lower - 36 pF.
So if I were to choose a 2A3 driver for a 300B, the 'predriver' would see a more capactive load that if it were to drive the 300B directly. Cause for thought.
...and have tried to argue (poorly) that same pint in the past.
Cheers
RC
Tre', That was sort of my point. I know intellectually that ECC99, 5687, 7119, etc, should make a "better" driver stage, on paper for sure, but like you I am very fond of 6SN7 and have found it hard to get around its mystique. (In fact, I started acquiring 7119 and 5687 several years ago with the facts in mind, but I have never put the tubes to use. Truth be told, I have a couple of 6900s as well.) Knowing that you and others here do like those tubes as drivers in actual practice is helpful.
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