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Parts List for One Channel

Version 4.4/4.5 of the Amplifier

Transistors (Starred types are preferred.)

I tend to prefer Motorola if available. Motorola has spun off its semiconductor division, and it is now called On Semiconductor. In the process, they have discontinued many products. I have seen some mystery brand transistors that have really bad characteristics. If the transistor is labeled with a name brand manufacturer, it should give no problems. For Q1 — Q11, the first NPN type should be used if the first PNP type is used, etc. This also applies to Q16 — Q17 and to Q18 — Q21. I have seen students use all of the types of transistors that I have listed below with no problems. If you look at the specs, however, you will see why I prefer the starred types. Transistors can be substituted, provided the substitutes have similar specs to the ones below.

I have been told that the MPS8099/MPS8599 are no longer a «complementary» pair because the PNP is discontinued. ON Semiconductor states that the direct replacement for the MPS8599 is a MPSA56. In March 2003, I was told that the MPS8599 is back. ON Semiconductor is now supplying them.

Other possibilities for the MPS8099/MPS8599 are the ZTX651/ZTX751 which are available from Digi-Key.

Q1, Q2, Q5, Q7, Q9, Q10BVCEOIC(max)PD(max) at 25o C ambienthFE(min)fT(min)
MPS8099*80 V0.2 A350 mW100150 MHz
MPS809860 V0.2 A350 mW100150 MHz
MPSA0680 V0.5 A300 mW5050 MHz
MPSA0560 V0.5 A300 mW5050 MHz
2N521050 V0.05 A310 mW20030 MHz
Q3, Q4, Q6, Q8, Q11BVCEOIC(max)PD(max) at 25o C ambienthFE(min)fT(min)
MPS8599*80 V0.2 A350 mW100150 MHz
MPS859860 V0.2 A350 mW100150 MHz
MPSA5680 V0.5 A300 mW5050 MHz
MPSA5560 V0.5 A300 mW5050 MHz
2N508750 V0.05 A310 mW20030 MHz
Q13, Q14BVCEOIC(max)PD(max) at 25o C ambienthFE(min)fT(min)
2N3439*350 V1 A1 W4015 MHz
2N3440250 V1 A1 W4015 MHz
NTE396350 V1 A1 W3015 MHz
Q12, Q15BVCEOIC(max)PD(max) at 25o C ambienthFE(min)fT(min)
2N5415200 V1 A1 W3015 MHz
2N5416*300 V1 A1 W3015 MHz
NTE397350 V1 A10 W30?

I have not tried the NTE396 and NTE397 transistors. They are specified to be a complementary pair. The spec sheet for the NTE396 has two power ratings — 1 W and 5 W. It is not clear why they specify two. The spec sheet for the NTE397 only has one power rating and it does not give the gain bandwidth product fT.

Q16BVCEOIC(max)PD(max) with case at 25o ChFE(min)fT(min)
MJE15030*150 V8 A50 W2030 MHz
2N6474120 V4 A40 W154 MHz
Q17BVCEOIC(max)PD(max) with case at 25o ChFE(min)fT(min)
MJE15031*150 V8 A50 W2030 MHz
2N6476120 V4 A40 W154 MHz
Q18, Q20BVCEOIC(max)PD(max) with case at 25o ChFE(min)fT(min)
MJ15003*140 V20 A250 W252 MHz
MJ15001140 V15 A200 W252 MHz
Q19, Q21BVCEOIC(max)PD(max) with case at 25o ChFE(min)fT(min)
MJ15004*140 V20 A250 W252 MHz
MJ15002140 V15 A200 W252 MHz

Do not use plastic insulating caps over Q18 through Q21. These will keep the screws that hold the power transistors to their sockets from making contact to the transistor cases. The case is the collector and there will be no power supply voltage on the collectors. I had a student use these caps, and R41 through R44 caught on fire on his board, and he blew Q16 and Q17.

Apparently the 2N3439/2N3440 and 2N5415/2N5416 transistors are getting difficult to find. A possible manufacturer who has them listed on its web page is STMicroelectronics. The STMicroelectronics transistors are available from Arrow Electronics and Mouser Electronics. I would be interested if anyone knows of other sources for these transistors. I have been told that ON Semiconductor no longer makes these and transistors with the ON Semiconductor label may be counterfeit. The transistors are currently made by ST Microelectronics and Central Semiconductor.

As of June 2000, RadioShack.com has all of the transistors at good prices. They can be ordered through the web. You can see a list of their part numbers and prices. In spring 2002, students told me that RadioShack.com was selling its inventory at steep discounts and would soon be out of business. Formerly Tech America, this is the parts division of Radio Shack and is not connected with the retail stores.

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.)

Miscellaneous

  • P1 — 2 kohm, 3/8 inch square, single-turn, top-adjust, laydown version, cermet potentiometer (DigiKey 3386P-202-ND)
  • L1 — 10 to 12 turns #22 solid insulated wire wound tightly around R49 and soldered to the leads of R49 where they emerge from the resistor body. Click here to see an illustration. Solder one end of a piece of #22 solid wire to one end of R49. Wind the wire tightly around R49 to form L1. Clamp the windings to R49 with a small bench vise. Strip and solder the other end of L1 to R49. Do not use stranded wire.
  • Use only stranded wire to wire the chassis. Do not use solid wire. I recommend #18 or #20 stranded wire for all wiring except the wires that run from the circuit boards to the bias diodes in the heat sinks and to the bases of the output transistors. These are all low current leads and I recommend #22 stranded wire for them. The holes in my circuit boards are drilled for these size wires. Do not use wire that is too big to fit into the holes in the circuit boards.
  • Power Switch — Digikey (EG1858-ND). This is a rocker switch which has been used by a student and he told me that he had no problems with it sticking. I have seen so many rocker switches purchased by students stick that I hesitate to recommend one. Maybe this one is an exception.
  • Heat sinks for Q16 and Q17 are Aavid 5741B (DigiKey HS111-ND).
  • Heat sink for Q18 through Q21 is Wakefield 423K or equivalent. This heat sink has a black anodize finish. It measures 5.5 inches long by 4.75 inches wide by 2.63 inches high and has a thermal resistance of 0.67 degrees C/W. It is listed by Wakefield under their reference number 1025 extrusion. The Newark Electronics part number for the 423K heat sink is 58F511. It can be found on their web site. These heat sinks must be grounded to the central chassis ground. The black anodize finish is an insulating layer. I recommend sanding it off around one of the mounting holes, installing a solder lug under the screw for that hole, and soldering a wire to central ground. Use an ohmmeter to verify that the heat sinks connect to central ground. If you don’t want to drill the transistor holes in the heat sinks, the Wakefield 435AAAA is drilled for 4 TO-3 devices. It is a larger and more efficient heat sink than the 423K. I do not know what the clearance is between the transistors, so it may be impossible to drill the holes for the bias diodes in the center.
  • Sockets for Q18 through Q21 — DigiKey 4601K-ND, DigiKey 4513K-ND (Keystone 4513), or equivalent. The 4601K-ND sockets are sort of cheap and I recommend them only if you cannot find the better ones. They use No. 6 sheet metal screws to secure the sockets. Do not use machine screws with these sockets for they will not hold! The 4513K-ND are a little more expensive. They require #6-32 machine screws to secure the sockets. I have had some students who have had these sockets crack when the screws are tightened. Each screw should be alternately tightened a little until both are tight.
  • Insulating wafers must be installed between Q18 through Q21 and the heat sinks. I prefer the rubber type insulators which do not require heat sink compound (DigiKey/Bergquist BER100-ND). If you use mica insulators (DigiKey 4662K), they must be coated with heat sink compound. This stuff is very messy and will spread all over everything it comes in contact with. I once heard someone say that if at dot of it is placed on a wall near the floor, it will spread to the ceiling by the next day.
  • Input jacks are panel mount phono jacks (DigiKey 576K) which must be insulated from the chassis panel with mating shoulder washers. If the jacks rotate after they are tightened, the shoulders are too thick. In this case, use one shoulder washer and one flat washer on each jack. I prefer the Switchcraft brand of phono jacks that have the teflon insulating material. They are a little more expensive, but well worth the price. If you use the Switchcraft jacks, you must use one shoulder washer and one flat washer to insulate each from the chassis panel. The part numbers for these are S1028 and S1029. In addition, you need one flat solder lug washer for the ground connection to the jack. The lug is a Switchcraft accessory. The Switchcraft jacks are available from Allied Electronics.
  • Output jacks are 5-way binding posts (DigiKey J164 for red and J165 for black). Standard spacing between red and black jacks is 3/4 inch. You can also buy a dual 5-way binding post set, one for each channel. I like them better than the single ones, but they are more expensive. If you use them, tighten the nuts carefully. I once had one crack when I tightened the nuts. Install R50 and C25 on the output jacks. Connect the red jack to the circuit board loudspeaker output and the black jack to the central power supply ground.
  • The Antek chassis seem to be a good value. Their eBay store is here. I believe that this company will make custom designed chassis. You download their software and design it. Then they make it.
  • Here are some suggestions for the chassis: Bud Valuline model NHC-14156 or model HC-14103, Sescom model 3RU10, Hammond model RMCV190513BK1, Lansing model BF10-V02B, and smarthome.com model 873533. I have not seen any of these enclosures, but they look like they will work. My model numbers should be checked to be sure that I have the correct size. The enclosure must be at least 5.25 inches high, by 17 inches wide, by 9 inches deep.
  • Sescom Chassis Warning — On an amp built by a student who used this chassis, we had problems because the main heat sinks were not grounded. Not only does the rear panel have an insulating coating on it, but it appears to be electrically isolated from the rest of the chassis. If you use this chassis, sand the black anodize insulating layer from around one of the mounting screw holes on each heat sink. Use a tooth lockwasher under the screw head that holds the heat sink to the rear panel and a tooth solder lug under the nut inside the back panel. Solder a wire from the lug to central ground. You should verify with an ohmmeter that the heat sinks are grounded. You should also sand the area around the mounting hole for the central ground solder lugs to be sure they make electrical contact to the chassis bottom panel. The bottom panel also has some coating on it that acts as an insulator.
  • Power cord. I recommend the Digi-Key Q106-ND. The color code is as follows: ac hot — brown, ac neutral — blue, safety ground — green.
  • Some students mount their heat sinks inside the chassis and use a fan to circulate the air. A fan that one student found to be compact and quiet is the radioshack.com model 9002516. It measures 3.1 inches by 3.1 inches by 1.5 inches and its noise is rated at 26 dB SPL. He mounted the two heat sinks inside the chassis on the back panel and used a circular hole saw to cut holes in both side panels. He mounted the fan inside the box over one hole and a fan grill on the outside of the box over both holes. The chassis depth must be at least 12 inches to do this.

Some Recommended Parts Suppliers.

  • Radio Shack. This is the former Tech America, which changed its name to RadioShack.com. It is the parts division of Radio Shack, and is not connected with the retail stores. They have all transistors and many other parts. In the spring of 2002, students told me that RadioShack.com was selling its inventory at steep discounts and would soon be out of business.
  • DigiKey Corp., P.O. Box 677, Thief River Falls, MN 56701 (1-800-344-4539). Good source for resistors, capacitors, some transistors, and chassis hardware. Competitive pricing. This is a good company to buy from. I recommend all parts from DigiKey for which their parts numbers are listed.
  • Jameco Electronics, 1355 Shoreway Rd., Belmont, CA 94002 (1-415-592-8097). Similar to Digi-Key but less assortment.
  • MCM Electronics Inc., 650 Congress Park Dr., Centerville, OH 45459-4000 (1-513-434-0031). Source of transistors. They also have some interesting looking rack mount chassis.
  • Mouser Electronics, 958 North Main St., Mansfield, TX 76063, (1-817-483-0165). Source of transistors. I have been told they also have the mica capacitors.
  • Newark Electronics, 4801 N. Ravenswood Ave, Chicago, IL 60640-4409 (1-800-4-NEWARK). Industrial supplier.
  • Apex Jr. They may have good bargains on filter capacitors and other things.

Newark and Allied have regional sales offices in many metropolitan areas. There are many surplus electronics companies which advertise in electronics hobby magazines. The catalogs from as many such companies as possible should be obtained before acquiring parts for the amplifier. Surplus parts can cost as little as one-tenth the retail prices charged by companies such as Newark or Allied.

Power Supply for Two Channels

  • T1 — The power supply voltages should be in the range (+ and -) 56 V to 59 V with no load on the amplifier. There are several transformers that can be used. These are as follows:
    • AnTek AN-5440 500VA. At late 2008, this transformer is priced at $57 plus $10 for shipping. It has two 120V primary windings that can be wired in parallel and two 40V secondary windings that can be wired in series. I have not tried one of these transformers, but it looks like it will work. If the primaries are not wired correctly, the fluxes will cancel and the transformer will be a short circuit on the AC power line, and you don’t want that to happen. It looks to me that the two reds on the primary should be wired together and the blacks should be wired together. If the secondaries are not wired correctly, the voltages can cancel. It is not clear how to connect the secondaries, but I would guess that one blue should be wired to one green to form the center tap. Use an AC voltmeter across the two non-center tap leads to measure the AC output voltage. It should be close to 80V. I use a fused Variac transformer when verifying the wiring on new transformers, but not everyone has one of these.
    • Avel Lindberg Y236804 500VA, 40VAC/40VAC at $80. Avel Lindberg Inc., 47 South End Plaza, New Milford, CT 06776, 860-355-4711. Mastercard and VISA accepted.
    • Victoria Magnetics 80VCT@6A toroidal transformer (model 05090001) for $62 ($58 with a Georgia Tech student ID) or 80VCT@8A toroidal transformer for $82. These are made by John Snowden johnbob@bigchair.com at Victoria Magnetics, 5945 Peachtree Corners East, Norcross, GA 30071. The phone number is 770-448-8794. John can also make the E-I core transformers. I do not have the pricing information on these, but the cost should be less. The company John is affiliated with was in the process of moving from Norcross to north Georgia during the fall and winter of 2006. This could make it difficult to contact him. I do not know the status of his move as of 12/01/106.
    • Signal Model 80-6 (80 VCT@6A, use 115 V primary taps) or Model 80-4 (80VCT@4A), Signal Transformer, 500 Bayview Ave., Inwood, NY 11096 (1-516-239-7208). I have tested these. Many students used them in the earlier days of the amplifier. With an AC line voltage of 120 V rms, this transformer has a no-load AC secondary voltage of just under 87 V rms. The DC power supply voltages are + and — 58 V. The transformer description can be read here. I was told in June 2000 that Signal wants $120 plus $40 setup charges for the 6 A version. With prices like this, I don’t see how Signal can sell many transformers.
    • EWC Model RPT 80-6 (80VCT@6A) or Model RPT 80-4 (80VCT@4A) split-bobbin rectifier power transformers, EWC Inc., 385 Highway 33, Englishtown, NJ 07726 (1-732-446-3110). I have not tested these. They appear to be similar to the Signal transformers. I was told in June 2000 that EWC wants $120 for the 6 A version. Like Signal, the EWC price is ridiculous, but unlike Signal, they don’t want the setup charge.
    • Plitron Model 08A026000 (formerly ILP Model 8A026) (80VCT@6.25A) or Model 07A026000 (formerly ILP Model 7A026) (80VCT@3.75A). Plitron Manufacturing, 601 Magnetic Drive, Toronto, Ontario, Canada M3J 3J2 (1-416-667-9914). These are toroidal transformers. My lab amp has the ILP 8A026 in it. With an AC line voltage of 120 V rms, this transformer has a no-load secondary AC voltage of 85 V rms. The power supply votages are just over + and — 57 V. Plitron is the manufacturer and does not typically stock its own items. They will accept VISA orders with a delivery date of about 3 weeks. In early 1997, the cost of the 08A026000 was $76 (Canadian) each in quantities of 2.
    • Avel Model D4053 (80VCT@4.13A) or Model D4062 80VCT@6.63A), Avel Transformers, Inc., 47 South End Plaza, New Milford, CT 06776 (1-203-355-4711). I have not tested these. From some data provided by a correspondant, these transformers seem to have the same voltage rating as the ILP transformer I used in my lab amp.
    • Toroid Model 738.382 (76VCT@5A) or Model 749.382 (76VCT@6A), Toroid Corp. of Maryland, 608 Naylor Mill Rd., Salisbury, MD 21801-9627 (1-800-274-5793). I have not tested these.
  • BR1 — 200 V 25 A Bridge Rectifier (DigiKey 26MB20A-ND)
  • C1P, C2P — Electrolytic capacitors. The value of the capacitors should be about 8000 uF or greater. The dc voltage rating should be several volts greater than the power supply voltage or greater. The Mallory CGS123U075FF1, 12000 uFd, 75 V capacitor is a good example.
  • C3P — 0.1 uF 250 V capacitor (DigiKey E2104-ND). This capacitor suppresses RF generated by switching transients in the bridge rectifier.
  • S1 — 15 A or greater AC line switch. Warning! The rocker type switches that I have seen tend to stick. A toggle switch that makes a noticeable mechanical click when switched is recommended. The smoother sounding switches tend to stick.
  • PL — If a pilot light is desired, it should be wired in parallel with the transformer primary. A neon light with internal dropping resistor is recommended.
  • Standoffs — 3/4 inch threaded standoffs should be used to mount the circuit boards (DigiKey 1451EK-ND, threaded for 4-40 screws).
  • Fuses. F1 — 8 A slow blow. F2 through F5 — 5 A fast blow. Fuse holders that mount inside the chassis are recommended (DigiKey 3536K-ND for F1 and 3539K-ND for F2 through F5, the latter is a quad fuse holder).
  • I have seen some amplifiers make the speakers thump on turn-on. This is caused by the filter capacitors not being fully discharged. If desired, bleeder resistors can be wired in parallel with C1P and C2P to ensure that the they discharge completely. I recommend 3.9 kohm 2 watt resistors for this. The power dissipated in each resistor will be slightly less than 1 W. The resistors can be soldered to solder lugs attached to the terminals of C1P and C2P. If the discharge takes too long, you can go to smaller value resistors, but the power ratings must be increased. The power dissipated is the power supply voltage squared divided by the resistance. To be on the safe side, I like to have a power rating at least twice the power dissipated in a resistor.

Screw Hole Sizes

So many students have asked me what the correct hole sizes are for machine screws. For a clearance fit for a number 4 screw, use a number 31 drill bit (0.12 inch diameter). For a clearance fit for a number 6 screw, use a number 27 drill bit (0.144 inch diameter).