McIntosh MC60 Power Amplifier Schematic.pdf
PRE-AMP INPUT r II 0.5V. INPUT 0.5 Output Connections Using Octal Socket 4 ohms - pins 1 and 2 8 ohms - pins 1 and 3 16 ohms - pins 1 and 4 500/600 ohms - pins 7 and 8 (pin 6 is CT and ground) 70.7 Volts - pins 5 and 6 (pin 6 is ground) Pre-amplifier Input Socket Connections Pin 1 - ground Pin 2 - pre-amp input (2.5V) Pin 3 - not used Pin 4 - +360V at 3.5 ma. Pin 5 - not used Pin 6 - not used Pins 7 and 8 - 6.3V at 1 amp. Note 1 - This jumper strap may be removed if ungrounded low im pedance outputs are desired R1 500K Pot. (Gain Adj . ) CHI Plate Choke R2 100K CH2 Plate Choke R3 27K R4 3.3M Cl .lrof, 400V R5 560K, 5% C2 . 47mf, 200 V R6 3.3K C3 lOOmf, 12V R7 68 ohms, 5% C4 8mf, 250V R8 100K C5 .22mf, 400V R9 18K, 1W C6 470mmf, 500V R10 2.2M C7 .047mf, 600V Rll 1.3K, 5% C8 .047mf, 600V R12 27K, 5% C9 .25mf, 600V R13 30K, 5% CIO .25mf, 600V R14 220K C11A 3 5mf, 500V R15 220K CUB 80mf, 450V R16 not used C11C 15mf, 450V R17 12K*, 2W C12A 35mf, 500V R18 1.2K C12B 80mf, 450V R19 120K, 5% C12C 15rof, 450V H20 12K*, 2W C13 lOmf, 450V R21 1M C14 .47mf, 200V R22 820K R23 1M R24 220K R25 220K R26 1.8K R27 10K, 10W R28 10K, 2W R29 180K R30 250 ohm Pot, (hum adj .) R31 270K, 5% R32 220K R33 220K R34 220, 1W R35 220, 1W Matched to within 1% L SERIAL NO. 4496 AND UP VOLTAGE AND RESISTANCE CHART Tube Pin No. DC Volts No Signal DC Volts at 60W out AC Volts at 60W out Resistance in Ohms Unit OfT 12AX7 1 82 81 1.5 Inf. 2 0 0 .45 100K to 560K 3 1.1 1.1 .45 3.3K 6 360 310 0 10K* 7 108 108 0 1.2M* 8 111 110 0 Inf. 12AU7 1 284 240 8.4 40K* 2 82 81 1.5 Inf. 3 92 88 .5 18K 6 284 240 8.4 38K* 7 62 Approx. 67 Approx. 0 Inf. 8 92 88 .5 18K 12BH7 1 340 285 148 12K* 2 0 0 11.6 210K 3 16.5 15 .52 1.2K 6 340 285 148 12K* 7 0 0 11.2 21 OK 8 16.5 15 .52 1.2K 12AX7 1 430 365 106 45* 2 -45 -44 148 1M 3 -45 -45 148 140K 6 430 365 106 45* 7 -45 -44 148 1M 8 -45 -45 148 140K 6550 3 430 365 106 45* (Both 4 430 360 110 2500* Tubes) 5 -45 -45 148 140K 8 .8 -2.5 110 6 5U4GA 2 435 380 9.4 0* (Both 4 0 0 335 14 Tubes) 6 0 0 335 15 8 435 380 6.4 0* Pre-Amp 4 425 365 0 10K* Input Socket 5 0 0 .36 320K
