- on Audio/Video/Photography
- Published in issue 7/2009 on page 114
Improved Hybrid HeadPhone Amplifier
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.
Voltages measured w.r.t. circuit ground
T1/T6 base 0.7 V
T2/T7 base 1.4 V
T3/T8 base 3.8 V
T3/T8 Emitter 2.8 V
ECC82 grid 4 V
T10/T12 Emitter 6.2 V
T9/T11Base 0.67 V
ECC82 anodes 10 V
ECC82 pin 5 9.4 V
D2 (across device) 0.8 V
T5 VCE 1.3 V
R6/R14 (across device) 6.85 V
R1,R8,R9,R15 = 10k?
R2,R4,R10,R12 = 91k? (E96: 90k?9)
R3,R11 = 15k?
R5,R13 = 22?
R6,R14,R16,R17,R22,R23 = 1k?
R7 = 39k?
R18,R21,R24,R27 = 560?
R19,R25 = 33k?
R20,R26 = 8k?06
C1,C6 = 2?F2 100V, lead pitch 22.5mm (WxL = 10 x 26 mm abs. max.)
C10,C12 = 10?F 63V, lead pitch 22.5mm (WxL = 10 x 26 mm abs. max.)
C2,C7 = 100nF, MKT, lead pitch 5mm or 7.5mm
C3,C8,C11,C13 = 100?F 25V, lead pitch 2.5mm, diam. 8.5 mm max.
C4,C9 = 2200?F 25V, lead pitch 7.5mm, diam. 18mm max.
C5 = 1000 ?F 25V, lead pitch 5mm, diam. 10 mm max.
D1,D3 = red LED
D2 = 1N4004
T1,T2,T6,T7,T9,T10,T11,T12 = BC550C
T3,T5,T8 = BC517
T4 = BD139
V1 = ECC82 or 12AU7
9-pin (‘Noval’) PCB mount socket, e.g. Conrad Electronics # 120529
PCB, # 080310-1 from www.thepcbshop.com