Alright, I'll honestly admit I haven't looked at tube datasheet in 20-years, hence I'm more than a little rusty. However I was wondering if you fine gentlemen could shed some light on this?
I'm trying to calculate a bias point etc. for a pair of KT88s in PP with a ~4K UL OPT using a ~450V supply voltage. I'm looking at running the KT88s in triode mode, but would possibly like to explore CFB and super-triode mode using one of the torodial OPTs sold by Amplimo/Plytron (designed by Menno van der Veen).
I've looked at several datasheets, but considering I'll be running a pair of Genalex Gold Lions, this one seemed applicable:
http://www.jacmusic.com/KT88/kt88_spec_sheet.pdf
However I'm puzzled by the values and acronyms used for several parameters, for example:
Push-Pull. Class AB1.
Cathode Bias. Triode Connection.
Va, g 2(b) 400 485 V
Va, g 2(o) 349 442 V
Ia|g2(o) 2 x 76 2 x 94 ma
Ia|g2(max. sig) 2 x 80 2 x 101 ma
RL(a-a) 4 4 k ohms
-Vg1 40 (approx) 50 (approx) V
Pout 17 31 W
Dtot 5.6 1.5 %
I. M.* 5.6 5.6 %
Pa|g2(o) 2 x 26.5 2 x 40 W
Pa|g2(max. sig) 2 x 19 2 x 27 W
Rk 2 x 525 2 x 525 ohms
Vin(g1-g1)(pk) 140 114 V
Zout 2 1.9 k ohms
What do they mean by (b) and (o)? Also, when I look at the plots in the same datasheet and try to calculate the proper bias point for triode mode I arrive at different values? I'm sure I'm missing something, but I can't seem to put my finger on it.
Any tips/suggestions would be most appreciated!
I'm trying to calculate a bias point etc. for a pair of KT88s in PP with a ~4K UL OPT using a ~450V supply voltage. I'm looking at running the KT88s in triode mode, but would possibly like to explore CFB and super-triode mode using one of the torodial OPTs sold by Amplimo/Plytron (designed by Menno van der Veen).
I've looked at several datasheets, but considering I'll be running a pair of Genalex Gold Lions, this one seemed applicable:
http://www.jacmusic.com/KT88/kt88_spec_sheet.pdf
However I'm puzzled by the values and acronyms used for several parameters, for example:
Push-Pull. Class AB1.
Cathode Bias. Triode Connection.
Va, g 2(b) 400 485 V
Va, g 2(o) 349 442 V
Ia|g2(o) 2 x 76 2 x 94 ma
Ia|g2(max. sig) 2 x 80 2 x 101 ma
RL(a-a) 4 4 k ohms
-Vg1 40 (approx) 50 (approx) V
Pout 17 31 W
Dtot 5.6 1.5 %
I. M.* 5.6 5.6 %
Pa|g2(o) 2 x 26.5 2 x 40 W
Pa|g2(max. sig) 2 x 19 2 x 27 W
Rk 2 x 525 2 x 525 ohms
Vin(g1-g1)(pk) 140 114 V
Zout 2 1.9 k ohms
What do they mean by (b) and (o)? Also, when I look at the plots in the same datasheet and try to calculate the proper bias point for triode mode I arrive at different values? I'm sure I'm missing something, but I can't seem to put my finger on it.
Any tips/suggestions would be most appreciated!
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http://frank.pocnet.net/sheets/084/k/KT88_GEC.pdf
That's the Ur-Source.
Generally, the "o" indicates zero signal. I don't know why they show lower Va at that point, but it's consistent with the current draws shown.
That's the Ur-Source.
Generally, the "o" indicates zero signal. I don't know why they show lower Va at that point, but it's consistent with the current draws shown.
Thanks Stuart, that's very helpful indeed!
The lower Va with no signal present has me puzzled though, have they simply mixed up the two conditions in the datasheet? In that case the same values seem to have been copied over with just about every datasheet with no-one bothering to have a closer look?
I can't be the first person to notice right? Or am I being too anal retentive about this stuff perhaps? As an engineer I tend to want to get firm grips on things first before I poke the hot iron in ...
The lower Va with no signal present has me puzzled though, have they simply mixed up the two conditions in the datasheet? In that case the same values seem to have been copied over with just about every datasheet with no-one bothering to have a closer look?
I can't be the first person to notice right? Or am I being too anal retentive about this stuff perhaps? As an engineer I tend to want to get firm grips on things first before I poke the hot iron in ...
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