EHHA I Parts Lists


Parts List for Single Board

Amplifier Single Channel +/-30V Operation (Two required for stereo)

Part Quantity Description
Circuit Board
- 1 EHHA Amplifier Single Channel Board
Potentiometers
Volume 1 50kΩ or 100kΩ Dual Audio Taper
R6 1 100Ω Trimpot - Tube Balance Adjust
R21 1 1kΩ Trimpot - Output Bias Adjust
Resistors
R1 1 1/8W 1% Metal Film Resistor 1MΩ
R2, R11 2 1/8W 1% Metal Film Resistor 300Ω
R3, R4, R10, R14 4 1/8W 1% Metal Film Resistor 1kΩ
R5, R7 2 1/8W 1% Metal Film Resistor 47.5Ω
R8 1 1/8W 1% Metal Film Resistor 12kΩ
R9 1 1/8W 1% Metal Film Resistor 200Ω
R12 1 1/8W 1% Metal Film Resistor 10kΩ
R13 1 1/8W 1% Metal Film Resistor 1.2kΩ - See Tweaks
R15, R16, R17, R18, R26, R29 6 1/8W 1% Metal Film Resistor 100Ω
R19 1 1/8W 1% Metal Film Resistor 3.32kΩ
R22, R23 2 1/8W 1% Metal Film Resistor 33.2kΩ - See Tweaks
R30, R31 2 1/8W 1% Metal Film Resistor 200kΩ
R27, R28 2 1/8W 1% Metal Film Resistor 4.75kΩ
Capacitors
C1, C4, C5, C10, C11, C13, C14 7 Metalized Polyester/Polypropylene Film Capacitor 1u 63V
C2, C3 2 Mica Capacitor 2.2p 250V - See Tweaks and Performance
C6, C7 2 Metalized Polyester/Polypropylene Film Capacitor 100n 63V
C8 1 Metalized Polyester/Polypropylene Film 1n 63V
C9, C12 2 Aluminum Electrolytic 220u 50V
Diodes
D1, D2 2 Small Signal Diode - 1N4148
LED 1 3mm 1.2V - 5.2V LED
Transistors
Q1, Q2, Q4, Q5, Q10, Q11 6 Toshiba 2SA1145
Q3, Q6, Q7, Q12, Q13 5 Toshiba 2SC2705
Integrated Circuits
IC1 1 High Beta, JFET Input Single Opamp - OPA134
IC2 1 15V 100mA TO92 Negative Voltage Regulator - 79L15
IC3 1 15V 100mA TO92 Positive Voltage Regulator - 78L15
Vacuum Tubes
V1 1 Dual Triode 6GM8/ECC86
Miscellaneous
Heatsinks 2 TO-220 Vertical 1.65"L x 1.00"W x 2.5"H
Heatsink Mounting Kit 2 TO-220
Sockets 1 9 Pin PCB Mount Tube Socket
Connector 2 3 Pin Phoenix 651-1729131
Connector 1 2 Pin Phoenix 651-1729128

Components Unique to a Specific Version

Mosfet Output Amplifier

Part Quantity Description
Resistors
R20 1 1/8W 1% Metal Film Resistor 220Ω
R24 1 1/8W 1% Metal Film Resistor 33Ω
R25 1 1/8W 1% Metal Film Resistor 15Ω
R32, R33 2 2W 1% Metal Film Resistor 2.2Ω
Transistors
Q8M 1 IRFZ24N
Q9M 1 IRF9Z34N


BJT Output Amplifier

Part Quantity Description
Resistors
R20 1 1/8W 1% Metal Film Resistor 750Ω
R24 - Not Used
R25 - Not Used
R32, R33 2 2W 1% Metal Film Resistor 10Ω
Transistors
Q8B 1 MJE243
Q9B 1 MJE253

Resistors

  • All resistors except R32 and R33 are 1/8W 1% Metal Film type - 7mm lead spacing.
  • R32, R33 are 2W 1% Metal Film type - 12mm or less lead spacing.
  • RLED sets the current in the LED. Calculate RLED using the forumla RLED = ( 30 - VLED ) / ILED.
  • Calculate RLED power with the formula PRLED = ILED x ILED x RLED.

Trimpots

  • R6, R21 are 3/8" multi turn cermet - 0.100" lead spacing inline (e.g., Bournes 3296W).

Capacitors

  • C1, C4, C5, C10, C11, C13, C14 are Polyester/Polypropylene - 5mm lead spacing 5.5mm width.
  • C2, C3 are Metalized Mica - 5mm lead spacing, 2.5mm width.
  • C6, C7 are Polyester/Polypropylene Film -5mm lead spacing 2.5mm width.
  • C8 is Polyester/Polypropylene Film -2.5mm lead spacing 2.5mm width.
  • C9, C12 are Aluminum Electrolytic - 5mm lead spacing 13mm diameter.

Diodes

  • D1, D2 are DO-35.
  • LED is 3mm.

Transistors

  • Q1-Q7, Q10-Q13 are Tohsiba ECB devices.
  • Other small signal or audio transistors may be substituted, such as 2N5550/2N5401 or BC546/BC556, but these devices have different pinouts and will need to be rotated before being inserted into the pads.
  • Q8M, Q9M are complementary mosfets. Other types with same pinout and similar characteristics can be used. Output bias point may or may not adjust to 100mA.
  • Q8B, Q9B are complementary BJTs. Other types with the same pinout and similar characteristics can be used, such as BD139/BD140. Output bias point may or may not adjust to 100mA.

Heatsinks

  • For headphone amplifier use use Wakefield 647-15ABP or equivalent.
  • For speaker amplifier use Wakefield 647-25ABP or equivalent.

Integrated Circuits

  • IC1 is OPA134 single opamp, but any high β, jfet input opamp with the same pinout can be substituted.
  • WARNING: Do not use BJT input opamps as they will not satisfactorily zero the offset.
  • The is no reason to sub anything for the 78L15/79L15.

Tubes

  • The design center is the 6GM8/ECC86 tube. Other subs are possible, such as 6922 and 6H30. See the Tweaks section.