Article

Improved Hybrid HeadPhone Amplifier

Jeff Macaulay’s excellent single valve ECC82/12AU7 'Hybrid Headphone Amp' (HHA) published in spurred the author to implement some modifications culminating mainly in an additional input preamp. The resulting project was then slightly reworked In the Elektor Audio Labs and the result is shown here, along with a PCB design to Elektor standards.

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Materials

080310-PCB.pdf

Gerber file

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 the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.

The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.

PCB

Download Gerber file: 080310-1-V20

Extra info / Update

Specifications

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

Component list

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

Capacitors

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.

Semiconductors

D1,D3 = red LED

D2 = 1N4004

T1,T2,T6,T7,T9,T10,T11,T12 = BC550C

T3,T5,T8 = BC517

T4 = BD139

Miscellaneous

V1 = ECC82 or 12AU7

9-pin (‘Noval’) PCB mount socket, e.g. Conrad Electronics # 120529

PCB, # 080310-1 from www.thepcbshop.com