• on Audio/Video/Photography
  • Published in issue 1/2014 on page 26
About the article

Compact Tube Amplifier

Using ordinary power transformers

Compact Tube Amplifier
Many audiophiles have occasionally thought about building a tube amplifier, but they are deterred by the high cost, large enclosure, hefty transformers and complicated wiring harnesses. For all the people in this group, the author has developed a compact, low-cost option using readily available components, so that everyone can enjoy the warm sound of a tube amplifier in their living room or den.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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.

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The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
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(1%, .6W, 350V):
R1,R3,R6,R8,R9,R11,R12,R15,R16,R19,R25 = 1kOhm
R2,R14 = 100kOhm
R4,R17 = 680kOhm
R5,R18 = 10Ohm
R7,R13 = 47Ohm
R10 = 220Ohm
R20,R21 = 47kOhm
R22 = 2.7kOhm
R23 = 470Ohm
R24 = 10kOhm
R26 = 4.7kOhm
R27,R28 = 8.2Ohm
P1 = 10kOhm trimpot, 0.15W, horizontal mounting
P2 = 1kOhm trimpot, 0.15W, horizontal mounting
C1,C3,C5 = 100nF 250V, 5%, MKP, 5, 7.5, 10, 15 or 22.5mm pitch
C2,C8 = 100nF 100V, 10%, MKT, 5 or 7.5mm pitch
C4 = 47nF 250V, 10%, MKP, 5, 7.5 or 10 mm
C6 = 10µF 63V, radial, 2.5mm pitch, 6.3mm diam.
C7 = 10µF 250V, radial, 5mm pitch, 10 mm diam.
D1 = 1N5819
IC1 = LM337
V1,V2 = PCL86 or 14GW8
TR1 = power transformer, Block type FL 14/6, 2x115V primaries; 2x6V secondaries; 14 VA
TR2 = 1:5 audio transformer, e.g. LTEI19/KD-0703 (Conrad Electronics # 515701-89)
K1,JP2,JP3 = 2-pin pinheader, 0.1’’ pitch
K2,K4 = 2-way PCB screw terminal block, 5mm pitch
K3 = 2-way PCB screw terminal block, 7.5mm pitch
K5 = 3-pin pinheader, 0.1’’ pitch
JP1 = 4-pin pinheader, 0.1’’ pitch
3 or 4 jumpers for JP1, JP2, JP3
V1,V2 = tube socket, ceramic, 9-pin Noval, PCB mount
Heatsink for IC1, 30K/W (e.g. Fischer Elektronik SK 12 SA 32)
PCB # 130385-1
Power Supply
R1 = 270kOhm, .5W, 350V
R2 = 10kOhm, .25W, 250V
C1–C4 = 4.7nF 400V
C5–C8 = 47nF 100V ceramic
C9 = 100µF 350V
C10,C11 = 1000µF 50V
D1–D4 = 1N4007
D5–D8 = 1N5819
D9,D10 = LED, low-current
F1 = fuse, 200mA/T (115VAC: 400mA/T) with holder
F2 = fuse, 750mA/T with holder
K1,K2 = 2-way PCB screw terminal block, 7.5mm pitch
K3 = 2-way PCB screw terminal block, 5mm pitch
TR1 = power transformer, Block type FL 30/12, 2x115V primaries; 2x12V secondaries, 30VA
TR2 = power transformer, Block type FL 18/12, 2x115V primaries; 2x12V secondaries, 18 VA

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