Western electric kt 88 brochure

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Page 2 of 7 MAXIMUM RATINGS Absolute Design Maximum Units V a 800 800 V V g2 600 600 V V a, g 2 600 600 V V g 1 200 200 V P a 42 35 W P g2 8 6 W P a+g2 46 40 W I k 230 230 ma V h-k 250 200 V T bulb 250 250 degrees C R g1-k (cathode bias) P a|g2 < 135W 470 k ohm P a|g2 > 35W 270 k ohm R g1-k (fixed bias) P a|g2 < 135W 220 k ohm P a|g2 > 35W 100 k ohm CAPACITANCES (Measured on a cold unscreened valve) Triode Connection C g1-a.g.2 : 7.9pF C g1-all less a.g2 : 9.3pF C a.g2 -all less g1 : 17pF Tetrode Connection C g1-a : 1.2pF C al -all less a : 16pF C a -all less g1 : 12pF CHARACTERISTICS Tetrode Connected V a 250 V V g2 250 V I a 140 mA I g2 3 (approx) mA V g1 15 (approx) V g m 11.5 mA/V r a 12 ohms µ g1-g2 8 -- Triode Connected Va,g2 250 V I a+ g2 143 mA -V g1 15 approx V g m 12 mA/V r a 670 ohms µ 8 --

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Page 3 of 7 TYPICAL OPERATION Push-Pull. Class AB1. Cathode Bias. Tetrode Connection V a(b) 560 V Va(o) 521 V V g2 300 V I a(o) 2 x 64 mA I a(max. sig) 2 x 73 mA I g2(o) 2 x 1.7 mA I g2(max. sig) 2 x 9 mA R L(a-a) 9 kohm R k* 2 x 460 ohm -V g1 30 (approx) V P out 50 W D tot 3 % I.M. 11 % P a(o) 2 x 33 W P a(max. sig) 2 x 12 W P g2(o) 2 x 0.5 W P g2(max. sig) 2 x 2.7 W V in(g1-g1)(pk) 60 V *It is essential to use two separate cathode bias resistors. **Intermodulation distortion: measured using two input signals at 50 and 6000 hz (ratio of amplitudes 4:1) Push-Pull. Class AB1. Fixed Bias. Tetrode Connection Va(b) 560 V V a(o) 552 V V g2 300 V I a(o) 2 x 60 mA I a(max. sig) 2 x 145 mA I g2(o) 2 x 1.7 mA I g2(max. sig) 2 x 15 mA R L(a-a) 4.5 kohm -V g1 34 (approx) V P out 100 W D tot 2.5 % I.M. 10 % P a(o) 2 x 33 W P a(max. sig) 2 x 28 W P g2(o) 2 x 0.5 W P g2(max. sig) 2 x 4.5 W V in(g1-g1)(pk) 67 V *It is essential to provide two separately adjustable bias voltage sources, having a voltage adjustment range of 25%. **Intermodulation distortion: measured using two input signals at 50 and 6000 hz (ratio of amplitudes 4:1).