Leach amplifier
#Leach amplifier
#transient intermodulation distortion
#TIM
#slewing induced distortion
#SID
#dynamic intermodulation distortion
#DIM
#amplifier design
#1970s
Description: A hot topic of amplifier design in the 1970s was "transient intermodulation distortion" (TIM). Other names which were used for this phenomenon were "slewing induced distortion" (SID), and "dynamic intermodulation distortion" (DIM). TIM occurs when a transient input signal overloads the input stage of an amplifier, causing it to either cut off or to become nonlinear for a brief instant before the feedback signal arrives. If the input stage cuts off, the amplifier output slews and the amplifier produces hard TIM. If the input stage becomes nonlinear but does not cut off, the amplifier is said to exhibit soft TIM. The amplifier will drive a 4 ohm load to full power without current limiting. Depending on the power supply regulation, the output power with a 4 ohm load is as great as twice the power with an 8 ohm load. With loads lower than 2 ohms, the protection circuits limit the maximum output current, and thus the output power, to protect the output transistors. The amplifier is stable with capacitive loads and will drive electrostatic loudspeakers with no problems. The 2N3439/2N5415 pair is the one that I originally used for my prototype amplifiers. It is the complementary TO-5/TO-39 case pair recommended in the RCA Power Transistor Manual for audio amplifiers. For all practical purposes, the 2N3440 and 2N5416, respectively, are equivalent to the 2N3439 and the 2N5415 for the Low TIM amplifier.
Q12 - Q15 can run a little warm. I have never had problems with these running too hot. With the Version 4.4/4.5 amp, I have reduced the bias currents in these transistors just a little to keep them cooler. Although I don't think they are needed, you can put TO-5 clip-on heat sinks on them. There is not much room on the circuit board for the heat sinks, so they must have small fins. Another type of heat sink which will fit is in the shape of a flag (about 1 inch high by 3/4 inch wide) with rounded clips on one end that clip around the transistor. If you can't find them, they are easy to make from sheet metal flashing. The clips should make good mechanical contact to the transistor for good heat conduction. Diodes D1, D2, D3, D4, D11, D12 - 1N4004 (DigiKey 1N4004DICT-ND) D5, D6, D7, D8, D9, D10 - 1N4148 (DigiKey 1N4148DICT-ND) D13 through D16 - 1N5250B 20 V Zener (DigiKey 1N5250BDICT-ND, not used in Ver. 4.3) Capacitors (First type listed is preferred.) Some of the capacitor types specified below are ceramic. I have seen some of these exhibit non-linear effects, so I don't recommend them unless the mica types cannot be found. The ceramic dielectric in the capacitors can exhibit a piezoelectric effect which causes the spacing between the plates to vary with applied voltage. This causes the capacitance to vary with voltage. Indeed, on one occasion I could hear a ceramic capacitor "sing" when excited at its resonance frequency.
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND, 0.25 inch hole spacing) C2, C3, C15, C16, C23, C24, C25 - 0.1 uF, 100 V film (DigiKey P4725-ND, 0.4 inch or 0.2 inch hole spacing) C7, C12, C17, C18 - 0.1 uF, 50 V film (DigiKey P4525-ND, 0.2 inch hole spacing) C4, C5, C13, C14, C21, C22 - 100 uF, 63 V radial electrolytic (DigiKey P10343-ND, 0.2 inch hole spacing) C6 - Either a single non-polar capacitor or two polar capacitors can be used for C6. I recommend the non-polar capacitor. In this case, use a 220 uF, 16 V bi-polar electrolytic in the holes for C6A (DigiKey/Panasonic P1168-ND, 0.2 inch hole spacing) and solder a short circuit jumper in the holes for C6B. (Failure to install this jumper will result in the loss of all bass response.) For two polar capacitors, use a 330 uF, 16 V radial electrolytic for C6A and C6B (DigiKey P10246-ND). C8 - 180 pF mica (Arco DM15-181J or DigiKey 338-1082-ND, 0.25 inch hole spacing) C9 - 47 pF mica (Arco DM15-470J or DigiKey 338-1053-ND 5.9 mm hole spacing. The DigiKey 338-1084-ND has a 3 mm hole spacing but the leads can be bent to fit the circuit board) C10, C11 - 10 pF mica (Arco DM15-100J or DigiKey 338-1068-ND, 0.25 inch hole spacing) C19, C20 - 0.01 uF, 50 V film (DigiKey P4513-ND, 0.2 inch hole spacing) Resistors (1/4 W 5% carbon film or 1% metal film unless specified otherwise. Please use an ohmmeter to check the value of all resistors before soldering them to the circuit board.)
R1 - 20 kohm R2 - 2 kohm R3 through R10 - 300 ohm R11, R12, R27 - 1.2 kohm R13, R14 - 2.2 kohm 1/2 W (see note below, 3.6 kohm in Ver. 4.3) R15, R16 - 12 kohm (10 kohm in Ver. 4.3) R17 - R18 - 11 kohm R19 - 1.1 kohm R20 - 22 kohm R21, R22 - 30 ohm R23, R24 - 360 ohm R25, R26 - 1 kohm R28, R29 - 270 ohm R30, R31 - 3.9 kohm 1/2 W R32, R33, R51 - 82 ohm R34, R35 - 330 ohm (270 ohm in Ver. 4.3) R36 - 220 ohm - If you have a problem with the VBE multiplier or the bias diodes, the bias voltage can go too high and this resistor can smoke and possibly burn the circuit board. I recommend putting a 1/8 inch long piece of insulation stripped from a piece of hookup wire on each lead of this resistor before soldering it to the circuit board. The insulation will hold the resistor up off the circuit board in case it burns. If you wish, you can use a 1/2 watt resistor for R36. R37 through R40 - 680 ohm (changed from 470 on 4/4/2) R41 through R44 - 10 ohm 1/2 W (changed from 3.3 ohms 7/2/00) R45 through R48 - 0.33 ohm 5 W Wire Wound (DigiKey 0.33W-5-ND) R49, R50 - 10 ohm, 2 W ceramic or carbon composition. Allen-Bradley made the carbon composition resistors for many years, but they apparently no longer make them. Ohmite is another manufacturer who is phasing out their carbon composition resistors in favor of ceramic composition. Digi-Key sells the Ohmite ceramic resistor. The part number is OY100K-ND. It measures 7/8 inch long by 5/16 inch in diameter. Another resistor sold by Digi-Key is the ALSR5F-10-ND, 10 ohm, 5 W resistor. It is about the same size as the OY100K-ND. Digi-Key also sells smaller size carbon film 2 W resistors. Although these can be used, I prefer the larger ones to wind the inductor L1 around. My circuit boards are drilled to fit the ceramic and carbon film resistors. The holes must be enlarged for the older carbon composition units. We have found that Ack Radio sells a Dale CW-5 10 ohm resistor (I believe it is rated at 5 watts) that can be used to wind the inductor on. If you do not use the specified power supply voltages, you can calculate the values for R13 and R14 from the formula R13 = R14 = (V - 40)/8.2, where V is the power supply voltage. For example, for V = 58 V, the formula gives R13 = R14 = 2.2 kohm. Use the nearest 5% resistor value. (For the Ver. 4.3 amplifier, calculate the values for R13 and R14 from the formula R13 = R14 = (V - 38.2)/5.42, where V is the power supply voltage. For example, for V = 57.7 V, the formula gives R13 = R14 = 3.6 kohm.)
The amplifier design presented is focused on mitigating transient intermodulation distortion (TIM), which can significantly affect audio fidelity, particularly in high-performance applications. The design employs a robust output stage capable of driving a 4-ohm load to full power without current limiting, ensuring that the amplifier can deliver substantial output power, especially when the load impedance is reduced. The use of complementary transistors, specifically the 2N3439 and 2N5415 pairs, is crucial in achieving low TIM characteristics, as these components are optimized for audio applications.
The thermal management of the output transistors is addressed through careful biasing and the option to use clip-on heat sinks, which are designed to maintain efficient thermal dissipation. The circuit board layout is optimized for compactness, allowing for the integration of small heat sinks while ensuring that the mechanical contact for heat conduction is maintained.
The selection of diodes and capacitors is critical in maintaining signal integrity and performance. The use of 1N4004 and 1N4148 diodes provides reliable rectification and signal clipping capabilities, while the choice of mica and film capacitors minimizes non-linear effects that could contribute to distortion. The design specifies a mix of electrolytic and non-polar capacitors to handle various frequency responses effectively, ensuring that the bass response is preserved.
Resistor selection is also critical, with a mix of carbon film and metal film resistors used to ensure precision and stability. The circuit incorporates various resistor values to manage biasing and feedback, with specific attention given to components that may experience elevated temperatures, such as R36. The design includes recommendations for insulation to prevent potential damage from overheating.
Overall, the amplifier circuit is engineered to deliver high fidelity audio performance while addressing common issues associated with transient intermodulation distortion, ensuring a reliable and high-quality output suitable for demanding audio applications.A hot topic of amplifier design in the 1970s was "transient intermodulation distortion" (TIM). Other names which were used for this phenomenon were "slewing induced distortion" (SID), and "dynamic intermodulation distortion" (DIM). TIM occurs when a transient input signal overloads the input stage of an amplifier, causing it to either cut off or to become nonlinear for a brief instant before the feedback signal arrives.
If the input stage cuts off, the amplifier output slews and the amplifier produces hard TIM. If the input stage becomes nonlinear but does not cut off, the amplifier is said to exhibit soft TIM. The amplifier will drive a 4 ohm load to full power without current limiting. Depending on the power supply regulation, the output power with a 4 ohm load is as great as twice the power with an 8 ohm load. With loads lower than 2 ohms, the protection circuits limit the maximum output current, and thus the output power, to protect the output transistors.
The amplifier is stable with capacitive loads and will drive electrostatic loudspeakers with no problems. The 2N3439/2N5415 pair is the one that I originally used for my prototype amplifiers. It is the complementary TO-5/TO-39 case pair recommended in the RCA Power Transistor Manual for audio amplifiers.
For all practical purposes, the 2N3440 and 2N5416, respectively, are equivalent to the 2N3439 and the 2N5415 for the Low TIM amplifier. Q12 - Q15 can run a little warm. I have never had problems with these running too hot. With the Version 4.4/4.5 amp, I have reduced the bias currents in these transistors just a little to keep them cooler.
Although I don't think they are needed, you can put TO-5 clip-on heat sinks on them. There is not much room on the circuit board for the heat sinks, so they must have small fins. Another type of heat sink which will fit is in the shape of a flag (about 1 inch high by 3/4 inch wide) with rounded clips on one end that clip around the transistor. If you can't find them, they are easy to make from sheet metal flashing. The clips should make good mechanical contact to the transistor for good heat conduction. Diodes D1, D2, D3, D4, D11, D12 - 1N4004 (DigiKey 1N4004DICT-ND) D5, D6, D7, D8, D9, D10 - 1N4148 (DigiKey 1N4148DICT-ND) D13 through D16 - 1N5250B 20 V Zener (DigiKey 1N5250BDICT-ND, not used in Ver.
4.3) Capacitors (First type listed is preferred.) Some of the capacitor types specified below are ceramic. I have seen some of these exhibit non-linear effects, so I don't recommend them unless the mica types cannot be found.
The ceramic dielectric in the capacitors can exhibit a piezoelectric effect which causes the spacing between the plates to vary with applied voltage. This causes the capacitance to vary with voltage. Indeed, on one occasion I could hear a ceramic capacitor "sing" when excited at its resonance frequency.
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND, 0.25 inch hole spacing) C2, C3, C15, C16, C23, C24, C25 - 0.1 uF, 100 V film (DigiKey P4725-ND, 0.4 inch or 0.2 inch hole spacing) C7, C12, C17, C18 - 0.1 uF, 50 V film (DigiKey P4525-ND, 0.2 inch hole spacing) C4, C5, C13, C14, C21, C22 - 100 uF, 63 V radial electrolytic (DigiKey P10343-ND, 0.2 inch hole spacing) C6 - Either a single non-polar capacitor or two polar capacitors can be used for C6. I recommend the non-polar capacitor. In this case, use a 220 uF, 16 V bi-polar electrolytic in the holes for C6A (DigiKey/Panasonic P1168-ND, 0.2 inch hole spacing) and solder a short circuit jumper in the holes for C6B.
(Failure to install this jumper will result in the loss of all bass response.) For two polar capacitors, use a 330 uF, 16 V radial electrolytic for C6A and C6B (DigiKey P10246-ND). C8 - 180 pF mica (Arco DM15-181J or DigiKey 338-1082-ND, 0.25 inch hole spacing) C9 - 47 pF mica (Arco DM15-470J or DigiKey 338-1053-ND 5.9 mm hole spacing.
The DigiKey 338-1084-ND has a 3 mm hole spacing but the leads can be bent to fit the circuit board) C10, C11 - 10 pF mica (Arco DM15-100J or DigiKey 338-1068-ND, 0.25 inch hole spacing) C19, C20 - 0.01 uF, 50 V film (DigiKey P4513-ND, 0.2 inch hole spacing) Resistors (1/4 W 5% carbon film or 1% metal film unless specified otherwise. Please use an ohmmeter to check the value of all resistors before soldering them to the circuit board.) R1 - 20 kohm R2 - 2 kohm R3 through R10 - 300 ohm R11, R12, R27 - 1.2 kohm R13, R14 - 2.2 kohm 1/2 W (see note below, 3.6 kohm in Ver.
4.3) R15, R16 - 12 kohm (10 kohm in Ver. 4.3) R17 - R18 - 11 kohm R19 - 1.1 kohm R20 - 22 kohm R21, R22 - 30 ohm R23, R24 - 360 ohm R25, R26 - 1 kohm R28, R29 - 270 ohm R30, R31 - 3.9 kohm 1/2 W R32, R33, R51 - 82 ohm R34, R35 - 330 ohm (270 ohm in Ver. 4.3) R36 - 220 ohm - If you have a problem with the VBE multiplier or the bias diodes, the bias voltage can go too high and this resistor can smoke and possibly burn the circuit board.
I recommend putting a 1/8 inch long piece of insulation stripped from a piece of hookup wire on each lead of this resistor before soldering it to the circuit board. The insulation will hold the resistor up off the circuit board in case it burns. If you wish, you can use a 1/2 watt resistor for R36. R37 through R40 - 680 ohm (changed from 470 on 4/4/2) R41 through R44 - 10 ohm 1/2 W (changed from 3.3 ohms 7/2/00) R45 through R48 - 0.33 ohm 5 W Wire Wound (DigiKey 0.33W-5-ND) R49, R50 - 10 ohm, 2 W ceramic or carbon composition.
Allen-Bradley made the carbon composition resistors for many years, but they apparently no longer make them. Ohmite is another manufacturer who is phasing out their carbon composition resistors in favor of ceramic composition.
Digi-Key sells the Ohmite ceramic resistor. The part number is OY100K-ND. It measures 7/8 inch long by 5/16 inch in diameter. Another resistor sold by Digi-Key is the ALSR5F-10-ND, 10 ohm, 5 W resistor. It is about the same size as the OY100K-ND. Digi-Key also sells smaller size carbon film 2 W resistors. Although these can be used, I prefer the larger ones to wind the inductor L1 around. My circuit boards are drilled to fit the ceramic and carbon film resistors. The holes must be enlarged for the older carbon composition units. We have found that Ack Radio sells a Dale CW-5 10 ohm resistor (I believe it is rated at 5 watts) that can be used to wind the inductor on. If you do not use the specified power supply voltages, you can calculate the values for R13 and R14 from the formula R13 = R14 = (V - 40)/8.2, where V is the power supply voltage.
For example, for V = 58 V, the formula gives R13 = R14 = 2.2 kohm. Use the nearest 5% resistor value. (For the Ver. 4.3 amplifier, calculate the values for R13 and R14 from the formula R13 = R14 = (V - 38.2)/5.42, where V is the power supply voltage. For example, for V = 57.7 V, the formula gives R13 = R14 = 3.6 kohm.)
Q12 - Q15 can run a little warm. I have never had problems with these running too hot. With the Version 4.4/4.5 amp, I have reduced the bias currents in these transistors just a little to keep them cooler. Although I don't think they are needed, you can put TO-5 clip-on heat sinks on them. There is not much room on the circuit board for the heat sinks, so they must have small fins. Another type of heat sink which will fit is in the shape of a flag (about 1 inch high by 3/4 inch wide) with rounded clips on one end that clip around the transistor. If you can't find them, they are easy to make from sheet metal flashing. The clips should make good mechanical contact to the transistor for good heat conduction. Diodes D1, D2, D3, D4, D11, D12 - 1N4004 (DigiKey 1N4004DICT-ND) D5, D6, D7, D8, D9, D10 - 1N4148 (DigiKey 1N4148DICT-ND) D13 through D16 - 1N5250B 20 V Zener (DigiKey 1N5250BDICT-ND, not used in Ver. 4.3) Capacitors (First type listed is preferred.) Some of the capacitor types specified below are ceramic. I have seen some of these exhibit non-linear effects, so I don't recommend them unless the mica types cannot be found. The ceramic dielectric in the capacitors can exhibit a piezoelectric effect which causes the spacing between the plates to vary with applied voltage. This causes the capacitance to vary with voltage. Indeed, on one occasion I could hear a ceramic capacitor "sing" when excited at its resonance frequency.
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND, 0.25 inch hole spacing) C2, C3, C15, C16, C23, C24, C25 - 0.1 uF, 100 V film (DigiKey P4725-ND, 0.4 inch or 0.2 inch hole spacing) C7, C12, C17, C18 - 0.1 uF, 50 V film (DigiKey P4525-ND, 0.2 inch hole spacing) C4, C5, C13, C14, C21, C22 - 100 uF, 63 V radial electrolytic (DigiKey P10343-ND, 0.2 inch hole spacing) C6 - Either a single non-polar capacitor or two polar capacitors can be used for C6. I recommend the non-polar capacitor. In this case, use a 220 uF, 16 V bi-polar electrolytic in the holes for C6A (DigiKey/Panasonic P1168-ND, 0.2 inch hole spacing) and solder a short circuit jumper in the holes for C6B. (Failure to install this jumper will result in the loss of all bass response.) For two polar capacitors, use a 330 uF, 16 V radial electrolytic for C6A and C6B (DigiKey P10246-ND). C8 - 180 pF mica (Arco DM15-181J or DigiKey 338-1082-ND, 0.25 inch hole spacing) C9 - 47 pF mica (Arco DM15-470J or DigiKey 338-1053-ND 5.9 mm hole spacing. The DigiKey 338-1084-ND has a 3 mm hole spacing but the leads can be bent to fit the circuit board) C10, C11 - 10 pF mica (Arco DM15-100J or DigiKey 338-1068-ND, 0.25 inch hole spacing) C19, C20 - 0.01 uF, 50 V film (DigiKey P4513-ND, 0.2 inch hole spacing) Resistors (1/4 W 5% carbon film or 1% metal film unless specified otherwise. Please use an ohmmeter to check the value of all resistors before soldering them to the circuit board.)
R1 - 20 kohm R2 - 2 kohm R3 through R10 - 300 ohm R11, R12, R27 - 1.2 kohm R13, R14 - 2.2 kohm 1/2 W (see note below, 3.6 kohm in Ver. 4.3) R15, R16 - 12 kohm (10 kohm in Ver. 4.3) R17 - R18 - 11 kohm R19 - 1.1 kohm R20 - 22 kohm R21, R22 - 30 ohm R23, R24 - 360 ohm R25, R26 - 1 kohm R28, R29 - 270 ohm R30, R31 - 3.9 kohm 1/2 W R32, R33, R51 - 82 ohm R34, R35 - 330 ohm (270 ohm in Ver. 4.3) R36 - 220 ohm - If you have a problem with the VBE multiplier or the bias diodes, the bias voltage can go too high and this resistor can smoke and possibly burn the circuit board. I recommend putting a 1/8 inch long piece of insulation stripped from a piece of hookup wire on each lead of this resistor before soldering it to the circuit board. The insulation will hold the resistor up off the circuit board in case it burns. If you wish, you can use a 1/2 watt resistor for R36. R37 through R40 - 680 ohm (changed from 470 on 4/4/2) R41 through R44 - 10 ohm 1/2 W (changed from 3.3 ohms 7/2/00) R45 through R48 - 0.33 ohm 5 W Wire Wound (DigiKey 0.33W-5-ND) R49, R50 - 10 ohm, 2 W ceramic or carbon composition. Allen-Bradley made the carbon composition resistors for many years, but they apparently no longer make them. Ohmite is another manufacturer who is phasing out their carbon composition resistors in favor of ceramic composition. Digi-Key sells the Ohmite ceramic resistor. The part number is OY100K-ND. It measures 7/8 inch long by 5/16 inch in diameter. Another resistor sold by Digi-Key is the ALSR5F-10-ND, 10 ohm, 5 W resistor. It is about the same size as the OY100K-ND. Digi-Key also sells smaller size carbon film 2 W resistors. Although these can be used, I prefer the larger ones to wind the inductor L1 around. My circuit boards are drilled to fit the ceramic and carbon film resistors. The holes must be enlarged for the older carbon composition units. We have found that Ack Radio sells a Dale CW-5 10 ohm resistor (I believe it is rated at 5 watts) that can be used to wind the inductor on. If you do not use the specified power supply voltages, you can calculate the values for R13 and R14 from the formula R13 = R14 = (V - 40)/8.2, where V is the power supply voltage. For example, for V = 58 V, the formula gives R13 = R14 = 2.2 kohm. Use the nearest 5% resistor value. (For the Ver. 4.3 amplifier, calculate the values for R13 and R14 from the formula R13 = R14 = (V - 38.2)/5.42, where V is the power supply voltage. For example, for V = 57.7 V, the formula gives R13 = R14 = 3.6 kohm.)
The amplifier design presented is focused on mitigating transient intermodulation distortion (TIM), which can significantly affect audio fidelity, particularly in high-performance applications. The design employs a robust output stage capable of driving a 4-ohm load to full power without current limiting, ensuring that the amplifier can deliver substantial output power, especially when the load impedance is reduced. The use of complementary transistors, specifically the 2N3439 and 2N5415 pairs, is crucial in achieving low TIM characteristics, as these components are optimized for audio applications.
The thermal management of the output transistors is addressed through careful biasing and the option to use clip-on heat sinks, which are designed to maintain efficient thermal dissipation. The circuit board layout is optimized for compactness, allowing for the integration of small heat sinks while ensuring that the mechanical contact for heat conduction is maintained.
The selection of diodes and capacitors is critical in maintaining signal integrity and performance. The use of 1N4004 and 1N4148 diodes provides reliable rectification and signal clipping capabilities, while the choice of mica and film capacitors minimizes non-linear effects that could contribute to distortion. The design specifies a mix of electrolytic and non-polar capacitors to handle various frequency responses effectively, ensuring that the bass response is preserved.
Resistor selection is also critical, with a mix of carbon film and metal film resistors used to ensure precision and stability. The circuit incorporates various resistor values to manage biasing and feedback, with specific attention given to components that may experience elevated temperatures, such as R36. The design includes recommendations for insulation to prevent potential damage from overheating.
Overall, the amplifier circuit is engineered to deliver high fidelity audio performance while addressing common issues associated with transient intermodulation distortion, ensuring a reliable and high-quality output suitable for demanding audio applications.A hot topic of amplifier design in the 1970s was "transient intermodulation distortion" (TIM). Other names which were used for this phenomenon were "slewing induced distortion" (SID), and "dynamic intermodulation distortion" (DIM). TIM occurs when a transient input signal overloads the input stage of an amplifier, causing it to either cut off or to become nonlinear for a brief instant before the feedback signal arrives.
If the input stage cuts off, the amplifier output slews and the amplifier produces hard TIM. If the input stage becomes nonlinear but does not cut off, the amplifier is said to exhibit soft TIM. The amplifier will drive a 4 ohm load to full power without current limiting. Depending on the power supply regulation, the output power with a 4 ohm load is as great as twice the power with an 8 ohm load. With loads lower than 2 ohms, the protection circuits limit the maximum output current, and thus the output power, to protect the output transistors.
The amplifier is stable with capacitive loads and will drive electrostatic loudspeakers with no problems. The 2N3439/2N5415 pair is the one that I originally used for my prototype amplifiers. It is the complementary TO-5/TO-39 case pair recommended in the RCA Power Transistor Manual for audio amplifiers.
For all practical purposes, the 2N3440 and 2N5416, respectively, are equivalent to the 2N3439 and the 2N5415 for the Low TIM amplifier. Q12 - Q15 can run a little warm. I have never had problems with these running too hot. With the Version 4.4/4.5 amp, I have reduced the bias currents in these transistors just a little to keep them cooler.
Although I don't think they are needed, you can put TO-5 clip-on heat sinks on them. There is not much room on the circuit board for the heat sinks, so they must have small fins. Another type of heat sink which will fit is in the shape of a flag (about 1 inch high by 3/4 inch wide) with rounded clips on one end that clip around the transistor. If you can't find them, they are easy to make from sheet metal flashing. The clips should make good mechanical contact to the transistor for good heat conduction. Diodes D1, D2, D3, D4, D11, D12 - 1N4004 (DigiKey 1N4004DICT-ND) D5, D6, D7, D8, D9, D10 - 1N4148 (DigiKey 1N4148DICT-ND) D13 through D16 - 1N5250B 20 V Zener (DigiKey 1N5250BDICT-ND, not used in Ver.
4.3) Capacitors (First type listed is preferred.) Some of the capacitor types specified below are ceramic. I have seen some of these exhibit non-linear effects, so I don't recommend them unless the mica types cannot be found.
The ceramic dielectric in the capacitors can exhibit a piezoelectric effect which causes the spacing between the plates to vary with applied voltage. This causes the capacitance to vary with voltage. Indeed, on one occasion I could hear a ceramic capacitor "sing" when excited at its resonance frequency.
C1 - 390 pF mica (Arco DM15-391J or DigiKey 338-1057-ND, 0.25 inch hole spacing) C2, C3, C15, C16, C23, C24, C25 - 0.1 uF, 100 V film (DigiKey P4725-ND, 0.4 inch or 0.2 inch hole spacing) C7, C12, C17, C18 - 0.1 uF, 50 V film (DigiKey P4525-ND, 0.2 inch hole spacing) C4, C5, C13, C14, C21, C22 - 100 uF, 63 V radial electrolytic (DigiKey P10343-ND, 0.2 inch hole spacing) C6 - Either a single non-polar capacitor or two polar capacitors can be used for C6. I recommend the non-polar capacitor. In this case, use a 220 uF, 16 V bi-polar electrolytic in the holes for C6A (DigiKey/Panasonic P1168-ND, 0.2 inch hole spacing) and solder a short circuit jumper in the holes for C6B.
(Failure to install this jumper will result in the loss of all bass response.) For two polar capacitors, use a 330 uF, 16 V radial electrolytic for C6A and C6B (DigiKey P10246-ND). C8 - 180 pF mica (Arco DM15-181J or DigiKey 338-1082-ND, 0.25 inch hole spacing) C9 - 47 pF mica (Arco DM15-470J or DigiKey 338-1053-ND 5.9 mm hole spacing.
The DigiKey 338-1084-ND has a 3 mm hole spacing but the leads can be bent to fit the circuit board) C10, C11 - 10 pF mica (Arco DM15-100J or DigiKey 338-1068-ND, 0.25 inch hole spacing) C19, C20 - 0.01 uF, 50 V film (DigiKey P4513-ND, 0.2 inch hole spacing) Resistors (1/4 W 5% carbon film or 1% metal film unless specified otherwise. Please use an ohmmeter to check the value of all resistors before soldering them to the circuit board.) R1 - 20 kohm R2 - 2 kohm R3 through R10 - 300 ohm R11, R12, R27 - 1.2 kohm R13, R14 - 2.2 kohm 1/2 W (see note below, 3.6 kohm in Ver.
4.3) R15, R16 - 12 kohm (10 kohm in Ver. 4.3) R17 - R18 - 11 kohm R19 - 1.1 kohm R20 - 22 kohm R21, R22 - 30 ohm R23, R24 - 360 ohm R25, R26 - 1 kohm R28, R29 - 270 ohm R30, R31 - 3.9 kohm 1/2 W R32, R33, R51 - 82 ohm R34, R35 - 330 ohm (270 ohm in Ver. 4.3) R36 - 220 ohm - If you have a problem with the VBE multiplier or the bias diodes, the bias voltage can go too high and this resistor can smoke and possibly burn the circuit board.
I recommend putting a 1/8 inch long piece of insulation stripped from a piece of hookup wire on each lead of this resistor before soldering it to the circuit board. The insulation will hold the resistor up off the circuit board in case it burns. If you wish, you can use a 1/2 watt resistor for R36. R37 through R40 - 680 ohm (changed from 470 on 4/4/2) R41 through R44 - 10 ohm 1/2 W (changed from 3.3 ohms 7/2/00) R45 through R48 - 0.33 ohm 5 W Wire Wound (DigiKey 0.33W-5-ND) R49, R50 - 10 ohm, 2 W ceramic or carbon composition.
Allen-Bradley made the carbon composition resistors for many years, but they apparently no longer make them. Ohmite is another manufacturer who is phasing out their carbon composition resistors in favor of ceramic composition.
Digi-Key sells the Ohmite ceramic resistor. The part number is OY100K-ND. It measures 7/8 inch long by 5/16 inch in diameter. Another resistor sold by Digi-Key is the ALSR5F-10-ND, 10 ohm, 5 W resistor. It is about the same size as the OY100K-ND. Digi-Key also sells smaller size carbon film 2 W resistors. Although these can be used, I prefer the larger ones to wind the inductor L1 around. My circuit boards are drilled to fit the ceramic and carbon film resistors. The holes must be enlarged for the older carbon composition units. We have found that Ack Radio sells a Dale CW-5 10 ohm resistor (I believe it is rated at 5 watts) that can be used to wind the inductor on. If you do not use the specified power supply voltages, you can calculate the values for R13 and R14 from the formula R13 = R14 = (V - 40)/8.2, where V is the power supply voltage.
For example, for V = 58 V, the formula gives R13 = R14 = 2.2 kohm. Use the nearest 5% resistor value. (For the Ver. 4.3 amplifier, calculate the values for R13 and R14 from the formula R13 = R14 = (V - 38.2)/5.42, where V is the power supply voltage. For example, for V = 57.7 V, the formula gives R13 = R14 = 3.6 kohm.)
amp design
ESP - The Audio Pages. Amplifier design techniques, find out how amplifiers work, and how to design them.
Amplifiers are critical components in audio systems, serving to increase the amplitude of audio signals to drive speakers or other output devices. The...