Parts list for standard configuration
The table below illustrates a standard configuration β22 board.
This configuration has a voltage gain of 8 (18dB). You must multiply
the quantity by the number of boards you're building (except for
enclosure-related and panel-mount items). See the sections below for
specific parts recommendations and options. Items shown in
italic are available from the
AMB audio shop.
| Part | Quantity | Description |
|---|
| Circuit board |
|---|
| - | 1 | β22 printed circuit board |
| Resistors |
|---|
| R1 | 1 | 1/8W 1% metal film resistor 475Ω (see table below) |
| R2 | 1 | 1/8W 1% metal film resistor 1MΩ (see table below) |
| R3 | 1 | 1/8W 1% metal film resistor 182Ω (see table below) |
| R4 | 1 | 1/8W 1% metal film resistor 1.21KΩ (see table below) |
| R5, R6 | 2 | 1/8W 1% metal-film resistor 49.9Ω |
| R7, R8 | 2 | 1/8W 1% metal-film resistor 56.2Ω |
| R9-R12, R25, R26 | 6 | 1/8W 1% metal-film resistor 2.21KΩ |
| R13, RLED+, RLED- | 3 | 1/8W 1% metal-film resistor 10KΩ |
| R14, R15 | 2 | 1/8W 1% metal-film resistor 121Ω |
| R16-R19 | 4 | 1/8W 1% metal-film resistor 10Ω |
| R20, R21 | 2 | 1/8W 1% metal-film resistor 249Ω |
| R22, R27 | 2 | 1/8W 1% metal-film resistor 562Ω |
| R23, R24 | 2 | 1/8W 1% metal-film resistor 1.82KΩ |
| R30, R31 | 2 | 0Ω (wire jumper) |
| R28, R29, R32 | 3 | 1/8W 1% metal-film resistor 75Ω |
| R33 | 1 | 1/8W 1% metal-film resistor 33.2Ω |
| R34, R35 | 2 | 2W 5% metal-oxide resistor 0.47Ω |
| Rz | 1 | 2W 5% metal-oxide resistor 22Ω (Zobel resistor, see Wiring & ground)) |
| Rg | 1 | 5W wirewound resistor 10Ω
(Ground loop breaker resistor, see Wiring & ground)) |
| Potentiometers |
|---|
| VR1 | 1 | 3/8" multi-turn cermet trimpot 200Ω |
| VR2 | 1 | 3/8" multi-turn cermet trimpot 500Ω |
| VR3 | 1 | 3/8" multi-turn cermet trimpot 5KΩ |
| Volume | 1 | Alps RK27112A 50KΩ dual log taper, panel-mount
(for 2-ch and 3-ch configurations only) |
| Volume | 1 | 50KΩ quad log taper, panel-mount
(for 4-ch balanced configuration only) |
| Capacitors |
|---|
| C1-C5 | 5 | multilayer ceramic capacitor 33pF (see table below) |
| C6-C8, C13, C14, C17, C18 | 7 | metallized polyester capacitor 1µF
|
| C9-C12 | 4 | aluminum electrolytic capacitor 100µF 50V |
| C15, C16 | 2 | aluminum electrolytic capacitor 470µF 50V |
| Cz | 1 | metallized polyester or X7R multilayer ceramic capacitor 0.047µF 100V (Zobel capacitor, see Wiring & ground)) |
| Cg | 1 | metallized polyester capacitor 0.1µF 250VAC class X or Y (Ground loop breaker capacitor, see Wiring & ground)) |
| Transistors |
|---|
| Q1, Q2 | 2 | N-channel JFET 2SK170BL |
| Q3, Q4 | 2 | P-channel JFET 2SJ74BL |
| Q5, Q6, Q11, Q12, Q15, Q16, Q17, Q25 | 8 | NPN small signal BJT BC550C |
| Q7, Q8, Q9, Q10, Q13, Q14, Q18, Q26 | 8 | PNP small signal BJT BC560C |
| Q19, Q20 | 2 | N-channel JFET PN4392 |
| Q21, Q23 | 2 | International Rectifier N-channel power MOSFET IRFZ24N |
| Q22, Q24 | 2 | International Rectifier P-channel power MOSFET IRF9Z34N |
| Diodes |
|---|
| D1, D2, D5-D10 | 8 | 12V 500mW zener diode BZX55C12 |
| D3, D4 | 2 | small signal diode 1N4148 |
| D11, D12 | 2 | 1A rectifier diode 1N4004 |
| LED+, LED- | 1 or 2 | Your choice (superbright) |
| CR1-CR8 | 8 | Current regulator diode 0.56mA 1N5291 |
| Miscellaneous |
|---|
| - | 4 | TO-220 extruded heatsink Aavid-Thermalloy 529802B00000 1.5" |
| - | 4 | TO-220 heatsink mounting kit (if required, see notes below) |
| - | 1 | heatsink thermal compound (if required, see notes below) |
| J1, J2 | 1 | Molex KK 0.100" 2-circuit header |
| - | 2 | RCA phono jacks, panel-mount |
| - | 4 | XLR 3-pin female connector, panel-mount
(for 4-channel fully balanced configuration only) |
| - | 1 or more | 1/4"" stereo phone jack, panel-mount |
| - | 4 | 5-way binding post, panel-mount
(2 red, 2 black for speaker power amplifier application) |
| - | 4 | circuit board standoffs or spacers |
| - | - | hookup wire |
| - | - | heat-shrink tubing |
| - | 1 | chassis case (your choice, see below) |
| - | 4 | rubber feet for chassis case |
| - | - | imperial #4-40 or metric M3 machine screws, hex nuts |
| - | - | other hardware as needed |
Please note that in the 3-channel "active ground" configuration,
some part values in the ground channel differ from that of the left
and right channels. See the following table:
| Part | Left & Right channels | Ground channel |
|---|
| R1 | 475Ω | (not used) |
| R2 | 1MΩ | 1KΩ |
| R3 | (see table below) | 2.49KΩ |
| R4 | (see table below) | 2.49KΩ |
| C2-C5 | (see table below) | 100pF |
The following table shows the left and right channel part values
when building the β22 with a non-default voltage gain (gain of 8x is the default):
| L & R Part | Gain 11x | Gain 8x | Gain 5x | Gain 2x |
|---|
| R3 | 100Ω | 182Ω | 392Ω | 2.49KΩ |
| R4 | 1KΩ | 1.21KΩ | 1.5KΩ | 2.49KΩ |
| C2-C5 | 22pF | 33pF | 47pF | 100pF |
These values were carefully tuned for the an optimal combination of
speed/bandwidth and stability. The β22 should not be operated
with a gain of less than 2x.
Parts recommendations & options
To obtain the blank β22 circuit board and some related parts,
visit the
AMB audio shop.
You can get almost everything else from the vendors listed on the
AMB Audio DIY Page. The
favorite vendors are
Mouser
and
Digi-Key.
The following is a list of recommendations and options. Please read
through this carefully before you order any parts.
Resistors
- All except R34-R35, Rz and Rg: 1/8W or 1/4W 1% metal film type
Lead spacing 0.400"
- R34-R35: 2W 5% non-inductive metal oxide type
Lead spacing 0.700"
- Rz: 2W 5% non-inductive metal oxide type
Needed only if the β22 will be driving speakers
(see the Wiring & ground section).
- Rg: 5W wirewound type
Needed only for single-box chassis configuration (see the
Wiring & ground section).
- Vishay-Dale
CW Series silicon-coated wirewound
(Mouser 71-CW5-10, Digi-Key CWD-10CT-ND)
- Vishay-Dale
RS Series silicon-coated wirewound
(Mouser 71-RS5-10, Digi-Key RSC-10CT-ND)
- Vishay-Dale
CP Series cement-filled wirewound
(Digi-key CPRA-10-ND)
- Xicon
CR Series cement-filled wirewound
(Mouser 280-CR5-10-RC)
Notes about RLED+ and RLED-:
RLED+ and RLED- are the current limit resistors for the LEDs.
The optimum value of these resistors depends on your choice of LED. Use this
online LED resistor value calculator
to determine what value your RLED+ and RLED- should be.
Depending on the value of the resistor and the voltage drop across it,
you should be mindful to use a resistor rated at high enough power.
The actual power dissipation is computed by:
Watts = V2 / R
where V is the voltage dropped and R is the value of RLED+ or RLED-.
For example, if you use a 10KΩ resistor and the voltage dropped
is 29V, then the power dissipation will be about 0.08W. In this case a
1/8W or 1/4W resistor will work fine.
The type of resistor is not critical as long as it fits well.
Trimpots
VR1, VR2, VR3: 3/8" multi-turn cermet
200&Omega, 500Ω, 5KΩ
Lead spacing 0.100" inline
- Vishay-Sfernice
T93YA
(Mouser 72-T93YA-200, 72-T93YA-500, 72-T93YA-5K)
- Vishay-Spectrol
64W (Mouser 594-64W201, 594-64W501, 594-64W502)
- Vishay-BC CT94W (Digi-key CT94EW201-ND, CT94EW501-ND, CT94EW502-ND)
- Bourns
3296W
(Mouser 652-3296W-1-201, 652-3296W-1-501, 652-3296W-1-502;
Digi-Key 3296W-201LF-ND, 3296W-501LF-ND, 3296W-502LF-ND)
Panel-mount potentiometer
Volume: 50KΩ or 10KΩ dual log taper (for 2-channel or 3-channel configurations)
Volume: 50KΩ or 10KΩ quad log taper (for 4-channel balanced configuration)
Capacitors
- C1-C5: multilayer ceramic capacitor (NP0 or C0G)
22pF, 33pF, 47pF, 100pF (see table above)
Lead spacing 0.100" or 0.200"
- Kemet
Golden-max C315 series
(Mouser 22pF: 80-C315C220J1G, 33pF: 80-C315C330J1G,
47pF: 80-C315C470J1G; 100pF: 80-C315C101J1G;
Digi-Key 22pF: 399-4162-ND, 33pF: 399-4172-ND,
47pF: 399-4181-ND, 100pF: 399-4141-ND)
- Vishay
Mono-Kap series
(Digi-Key 22pF: BC1005CT-ND, 33pF: BC1007CT-ND,
47pF: BC1009CT-ND, 100pF: BC1013CT-ND)
- others
- C6, C8, C13, C14, C17, C18: metallized polyester film capacitor
1µF
Lead spacing 0.200"
- Wima
MKS2 (AMB audio shop; Mouser 505-MKS21/63/10)
- Vishay-BC
MKT370
(Mouser 594-2222-370-11105; Digi-Key BC1622-ND)
- Vishay-Roederstein
MKT1817 (Mouser 75-MKT1817510064)
- AVX BF/BQ series
(Mouser 581-BF074D0105J, Digi-Key 478-3367-ND)
- C9, C10, C11, C12: aluminum electrolytic capacitor 50V low-ESR high-reliability
100µF
Lead spacing 0.200", 10mm or 13mm diameter
- C15, C16: aluminum electrolytic capacitor 50V low-ESR high-reliability
470µF
Lead spacing 0.200", 13mm diameter or
Lead spacing 0.300", 18mm diameter
- Panasonic
FC
(Digi-Key P10328-ND or P11260-ND)
- Panasonic
FM
(Digi-Key P12400-ND)
- Nichicon
HE
(Mouser 647-UHE1H471MHD3)
- Nichicon
PW
(Mouser 647-UPW1H471MHD)
- Nichicon
KZ (Muse),
FW or
FG
("boutique")
- Vishay-BC
136 RVI series
- Elna
Silmic or Cerafine
("boutique")
- Cz: metallized polyester film or multilayer ceramic (X7R) capacitor 100V
0.047µF
Needed only if the β22 will be driving speakers (see the
Wiring & ground secion).
- Panasonic
ECQ-B(F) series
(Digi-Key P4652-ND)
- Panasonic
ECQ-E(F) series
(Digi-Key EF1473-ND)
- AVX BF/BQ series
(Mouser 581-BQ014E0473J, Digi-Key 478-3408-ND)
- Vishay-Roederstein
MKT1817 (Mouser 75-MKT1817347014)
- Vishay-Roederstein
MKT1818 (Mouser 75-MKT1818347014)
- Kemet
Aximax C430 series
(Mouser 80-C430C473K1R, Digi-Key 399-1851-1-ND)
- Cg: metallized polyester film capacitor 250VAC+
0.1µF
Needed only for single-box chassis configuration (see the
Wiring & ground secion).
- Panasonic
ECQ-UG series
(Digi-Key P11116-ND)
- Mallory (Cornell Dubilier)
158X series
(Mouser 539-158X104)
Diodes
- D1, D2, D5-D10:
Lead spacing 0.300"
- BZX55C12 12V 500mW zener diode, DO-35
(AMB audio shop, Mouser)
Please do not substitute with other types. The BZX55C12 has
low-noise characteristics important for this amplifier. See
Christer's measurements on diyaudio.com
for details.
- D3, D4: small signal diode 100V, DO-35
Lead spacing 0.300"
- 1N4148
(Mouser 512-1N4148, Digi-key 1N4148FS-ND)
- 1N914
(Mouser 512-1N914, Digi-key 1N914CT-ND)
- D11, D12: 1A rectifier diode 400V, DO-41
Lead spacing 0.300"
- 1N4004
(Mouser 512-1N4004, Digi-key 1N4004-E3/23GI-ND)
You may substitute this with any 1N4002-1N4007 diode.
- CR1-CR8: 0.56mA current regulator diode
DO-35, DO-41 or TO-92
(see the Instructions section)
- Central Semiconductor
1N5291
(AMB audio shop, Mouser)
- Vishay-Siliconix
J503
- Semitec
E-501
- J201 N-channel JFET, selected for Idss = 0.56mA ±10%
(Mouser 512-J201)
- LED:
Lead spacing 0.100"
Your choice of size and color (affects value of RLED+ and RLED-, see
notes above for RLED+ and RLED- for details)
Transistors
- Q1, Q2: N-channel small signal JFET
2SK170BL (TO-92), matched for Idss
(AMB audio shop, B&D Enterprises, MCM Electronics)
- Q3, Q4: P-channel small signal JFET
2SJ74BL (TO-92), matched for Idss
(AMB audio shop, B&D Enterprises, MCM Electronics)
- Q5, Q6, Q11, Q12, Q15, Q16, Q17, Q25: NPN small signal BJT
BC550C (TO-92)
(AMB audio shop, Mouser)
- Q7, Q8, Q9, Q10, Q13, Q14, Q18, Q26: PNP small signal BJT
BC560C (TO-92)
(AMB audio shop, Newark)
- Q19, Q20: N-channel small signal JFET
PN4392 (TO-92)
(AMB audio shop, Mouser, Digi-key)
- Q21, Q23: N-channel power MOSFET International Rectifier
IRFZ24N (TO-220AB)
(AMB audio shop, Digi-Key, Newark)
- Q22, Q24: P-channel power MOSFET International Rectifier
IRF9Z34N (TO-220AB)
(AMB audio shop, Digi-Key, Newark)
Notes about the transistors:
- See the Device matching section about
transistor matching.
- Do not substitute the transistors and MOSFETs with other types.
The compensation capacitors' values were tuned for optimum
performance with the specified devices. Changing to other types
may degrade the performance or cause instability.
- Do not mount the MOSFETs off-board on a remote heatsink. The
added wiring from the board to the MOSFETs may cause oscillations.
Heatsinks
Your choice of heatsink will affect chassis case compatibility due to height
and other mechanical/physical attributes.
Board-mount heatsinks:
- Aavid-Thermalloy
529802B00000 (onboard, 1.5" tall, screw-mount)
(AMB audio shop, Digi-Key)
- Aavid-Thermalloy
529802B02500 (onboard, 1.5" tall, pin-mount)
(Mouser, Digi-Key)
- Aavid-Thermalloy
529902B02500 (onboard, 2" tall, pin-mount)
(Mouser, Digi-Key)
- Aavid-Thermalloy
530002B02500 (onboard, 2.5" tall, pin-mount)
(Digi-Key)
- Wakefield
647-15ABP, 657-15ABP or 657-15ABPN
(onboard, 1.5" tall, pin-mount)
(Mouser, Digi-Key)
- Wakefield
657-20ABP (onboard, 2" tall, pin-mount)
(Mouser, Digi-Key)
Off-board heatsinks:
TO-220 heatsink mounting kit
If the tops of the heatsinks will be in close proximity to the top metal
cover when the board is installed in your chassis case, then you should mount
the MOSFETs to the heatsinks using TO-220 mounting kits, which electrically
isolate the MOSFETs' mounting tabs from the heatsinks. If you are using
offboard heatsinks, then TO-220 mounting kits are also required.
Otherwise, you may mount the MOSFETs to the heatsinks directly.
Heatsink thermal compound
Not needed if using mounting kits with Thermalsil or Sil-Pad isolators.
- Radio Shack
276-1372
- Wakefield 120-SA (Mouser 567-120-SA; Digi-Key 345-1006-ND)
- others
Connectors
PCB terminal headers
(optional, allows easy wiring connect/disconnect to PCB):
- Molex
KK 22-23-2021 0.100" header, 2-circuit
(Mouser 538-22-23-2021; Digi-Key WM4200-ND)
mating plug
22-01-3027
(Mouser 538-22-01-3027; Digi-Key WM2000-ND),
crimp terminals
08-50-0114
(Mouser 538-08-50-0114; Digi-Key WM1114-ND)
- other 0.100" connectors, 2-circuit
Chassis / case
Be sure to use a case that provides enough internal clearance for
the heatsinks you choose. If your heatsinks are not external to
the case (exposed fins), then you should cut ventilation slots in the
case (if not already so equipped) to ensure proper cooling.
The following are some examples of case styles that may be used
with the β22.
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