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In Reply to: RE: In what spirit do you ask the question ??.. posted by drlowmu on March 01, 2017 at 12:51:50
I'll typically be at 47 mA and about 260 P-K, or 12.22 Watts dissipation
At this bias point how many hours do you think you can get out of this tube? I know it's a 40W tube and at this dissipation it is loafing, but I still wonder what that number might be especially as compared to a regular 15W 2A3 that is run under the same conditions.
I would think a 300b operating at those points would last a lifetime.
And that's what a JJ 2a3-40 is, a 300b with folded filaments.
It does have the mu of a 2a3 but the same limiting values as their 300b.
450v, 40 watt, 70ma fixed bias and 100ma cathode biased
It has the same inter electrode capacitances and that's interesting because if the mu is different then the spacing between elements should be different but still the inter electrode capacitances are list as being the same.
I really think the two, the JJ 2a3-40 and the JJ 300b, are the same tube with the filament center tapped for the JJ 2a3-40 and the center tap is connected to one filament pin and the two ends are both connected to the other filament pin.
Have Fun and Enjoy the Music
"Still Working the Problem"
I think you're probably right on nearly all counts.
Interestingly, on JJ's website, there are several hints that the
2A3-40 handily outperforms their 300B. Pretty strong hints at that!
That's what has happened with me. For a long time, I just popped
the 2A3-40 into amps that had been voiced for other 2A3s-- the
likes of old RCA's, The EML mesh and solid-plate tubes, and etc.
Even Sovteks and Electro-Harmonix (a premium Sovtek-- has
gold-flashed grids, and does sound better. Looks like the
Kevin Hayes (VAC) had once mentioned that you had to voice
for the JJ tubes... they're different.
That they are! If I voice an amp for them, other tubes won't
be at their best. If I voice for those at their best, the
JJ sounds good, but fairly ordinary.
It's interesting that when you get the JJ 2A3-40 settled into
what it really wants, it can and will give you everything you
could ever ask for about recorded music. It will sound just
like that expensive Berkeley Audio Design DAC that costs
$16,000.00 That's saying a lot because that thing is GREAT!
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