THE M-O VALVE KT88 COMPANY LIMITED
BEAM TETRODE
BRIEF DATA
The KT88 has an absolute maximum anode dissipation rating of 42W and is designed for use in the output stage of an a.f. amplifier. Two valves in Class AB1 give a continuous output of up to 100W. The KT88 is also suitable for use as a series valve in a stabilised power supply. The KT88 is a commercial version of the CV5220 and is similar to the 6550.
HEATER
6.3 Vh . V Ih '(approx) . 1.6 A
MAXIMUM RATINGS
Absolute Design Maximum 800 800 Va v · 600 600 Vg2 V 600 600 Va,g2 . V 200 200 -Vg1· V 42 35 W Pa . 8 6 W Pg2 46 40 W Pa+g2 . Ik 230 230 mA . 250 200 V Vh-k . 250 250 QC Tbulb' Rg1.k (cathode bias) . 470 kQ Pa+g2 <,35W >35W . 270 kQ Pa+ g 2 Rg1-k (fixed bias) 35W 220 kQ Pa+g2 <, . . 100 kQ Pa+g2 >35W
CAPACITANCES (Measured on a cold unscreened valve)
Triode Connection Tetrode Connection
7 9 pF 1.2 pF Cg1-a,g2 · . . Cg1-a . 9.3 pF 16 pF Cg1-all less a,g2 cg1-allless a 17 F 12 pF Ca,g2-all less gl p ca·all less gl
A member of the GEC Group of Companies December 19 74 ©The M-O Valve Co. Ltd. Issue 5 CHARACTERISTICS
Tetrode Connected
Va· . . . 250 v V g2 .. . . 250 V la · . . . . 140 mA .3 Ig2 (approx) . mA -Vg1 (approx). 15 V 9m .. 11.5 mAN kn ra . 12 · I1g1-g2 . 8
Triode Connected
250 Va.g2 . . . . V 143 l a+g 2 . . . . mA a 15 -Vg1 ( pprox). V 1 gm · 2 mAN r a . 670 n 11 . .8
TYPICAL OPERATION
Push-Pull. Class AB1. Cathode Bias. Tetrode Connection
V 560 V a(b) . V 521 V a(o) . Vg2 300 V 2 x 64 mA la(o) la (max sig) 2 x 73 mA 1.7 Ig2(0)· . 2 x mA � mA 2 (max sig) . 2x 9 . 9 kn L(a-a) . . * Rk 2x 460 n -Vg1 (approx) . 30 V . . 50 W Pout . . . 3 % Dtot tl.M . . 1 1 % 2 x 33 W Pa(o) 2 x 12 W Pa(max sig ) 2 x 0 5 Pg2(0) . W � 2 x 2.7 W 2 (max sig)· . crest 60 V (g1-g1 ) (ac)
* It is essential to use two separate cathode bias resistors. tlntermodulation distortion; measL;;-ed using two input signals at 50 and 6000Hz (ratio of amplitudes 4; 1).
KT88 Page 2 Push-Pull. Class AB1. Fixed Bias. Tetrode Connection
560 Valb) . v 552 Valo) . V 300 Vg2 . V 2 x 60 mA lalo) . 2 x 145 mA la lmax sig) 2 x 1.7 mA Ig2(0)' . 2 x 15 mA 192 (max sig) . 4.5 kn RL(a-a) . . 34 *-Vgl (approx) V 100 W Pout . 2.5 % Otot . tl.M. 10 % 2 x 33 Pa(o) . W 2 x 28 Pa (max sig) W 2 x 0.5 Pg2(0)' W 2 x 4.5 Pg2 (max sig)· W 67 V(gl-gl }(ac) crest V
* It is essential to provide two separately adjustable bias voltage sources, having a voltage adjustment range of ±25%. '1'1ntermodulation distortion; measured using two input signals at 50 and 6000Hz (ratio of amplitudes 4: 1).
Push-Pull. Class AB1. Cathode Bias. Ultra-Linear Connection (40% Tapping Points)
. 500 375 Va,g2(b) . V . 436 328 Va,g2(0) . V 2 87 2 x 87 mA la+g2(0) . x 2 2 x 96 la+g2 (max sig) x 99 mA . .6 5 kn RUa.a) . 2 600 2 n *1'\ x x 400 52 35 -Vgl (approx). V 50 30 Pout . W 1.5 1 % Otot tl.M. 4 3 % 2 x 38 2 x 28.5 Pa+g2(o) W 2 x 17 2 x 16 Pa+g2 (max sig) . W 104 71 V V(gl.g1 }(ac) crest Zout . .4.8 4.5 kn
* It is essential to use two separate cathode bias resistors. 'tlntermodulation distortion; measured using two input signals at 50 and 6000Hz (ratio of amplitudes 4: 1).
KT88 Page 3 Push-Pull. Class AB1. Fixed Bias. Ultra-Linear Connection. (40% Tapping Points)
Va,g2(b) . 560 460 V Va,g2(o) . 553 453 V la+g2(o) 2 x 50 2 x 50 mA la+g2 (max sig) 2 x 157 2 x 140 mA RUa-a) .4.5 4 kn * -Vgl (approx) 75 59 V 100 70 Pout W .2 2 % Dtot 't'I.M. 11 10 %
Pa+g2(o) . 2 x 27.5 2 x 22.5 W 2 33 2 27 Pa+g2 (max sig) x x W 140 114 V(gl-gl )(ac) crest V .7 6.5 Zout . kn
* It is essential to provide two separately adjustable bias voltage sources, having a voltage adjustment range of ±25%. 't'lntermodulation distortion; measured using two input signals at 50 and 6000Hz (ratio of amplitudes 4: 1).
Push-Pull. Class AB1. Cathode Bias. Triode Connection
. 400 485 Va,g2(b) . V 349 422 Va,g2(o) . V 2 76 2 94 la+g2(o) x x mA 80 2 101 la+g2 (max sig) 2x x mA .4 4 RUa-a) kn 40, 50 -Vgl (approx) . V 17 31 Pout W . 1.5 1.5 % Dtot *I.M. .5.6 5.6 % 2 26.5 2 40 Pa+g2(o) x x W 2 19 2 27 Pa+g2 (max sig) x x W 2 525 2 525 n Rk· x x 114 V(gl-gl )(ac) crest 78 V .2 1.9 kn Zout
* I ntermodulation distortion; measl1red using two input signals at 50 and
6000Hz (ratio of a mplitudes 4: 1).
KT88 Page 4 INSTALLATION
The tube may be mounted either vertically or horizontally. When tubes are mounted vertically it is recommended that the centres of the tube sockets are not less than 4in. apart and that pins 4 and 8 of each tube are in line. When tubes are mounted horizontally it is recommended that the centres of the tube sockets are not less than 4in. apart and that pins 4 and 8 of each tube are in the same vertical line. One tube should not be mounted directly above another. Free air circulation around the tube is desirable.
OUTLINE
11011
Base: Metal shell wafer octal 110 52 dia
125 Pin: 1 base shell 5 g1 2 h 6 NP 3 a 7 h 4 g2 8 k.bp
Dimensions are in mm and are maximum
Whilst M-QV has taken care to ensure the accuracy of the information contained herein it accepts no responsibility for the consequences of any use thereof and also reserves the right to change the specification of goods without noti�e. M-QV accepts no liability beyond that set out in its statjdard conditions of sale in respect of infringement of third party patents arising from the use of tubes or other devices in accordance with information contained herein.
KT88 Page 5 100 Vql �OV 410
V.2 -IOOV
75
-4V
50 Iq1 (Vql 0) -bY
-8V 25 10V 12V « I ! 14V -'" 0 IbV 0 100 200 300 400 500 Va (V)
200 14" ql OV
Vq2 150V 2V 150 4V
bV 100 8V -IOV
50 12V 14V Iq2 Vql OV IbV � -18V E lOV
-'" 22V 01) 100 200 300 400 500 24V Va (V)
KT88 Page 6 ,.
300 ql-OV
-4V
200 -BV
o - 12V
100 ItN
20V I I I 4V
_fD 0 0 100 200 300 400 V. (V)
.4"
5V Vq2 3 00V
I --L
300 t-+- 10
I r ,
40V
_fO -45¥ 0 0 100 200 300 400 500 V. (V)
KT88 Page 7 300 Vql ,rN_ ,. , , I -�f± fj- 5V TRIODE CONNECTION 1-- r -IOV ; . �- 1 15V 200 , 20 + 25V 30V 35V, , 40-45V�'+f:: 4 I ' 100 I ,-' 50V 55V , 60V f.-L I -:-t7 -r: 65V ; I y -- - 70V :Y , f'l-x-' ,-j1 � lA _k!': , ...... 7W ? i$ 80V '00 I�200 300 400 500
400 OV 5V Vql 40% "1> �§§§§�����§j�§§§§§§������������I()V LT RA LINEAR CONNECTION TAP , - 300 , 7' 11111Y , '11 111111 -ill -+ [4- 200 ', � I sV 1 I , 4SV SOV, ,
tt, ...... '
- 100fft::;: 200 � 300 400 500 255 295 335 375 415 455 Vg2 (VI
The M-O Valve Company Limited kelth@snoo�eu KT88 Brook Green Works, London W6 7PE Page 8 Printed in England