About the article

Versatile Final Amplifier

audio power with many features

Versatile Final Amplifier
Only a few years ago, many music lovers turned up their noses on seeing a hybrid circuit or integrated circuit in a final amplifier, but now there is a new generation of output stage ICs that have been specially designed for use in highquality audio amplifiers.The Variable Final Amplifier is built using ST Microelectronics TDA7293 ICs, which have MOS outputs stages. This integrated power amplifier IC is a successor to the TDA7294, which was described a long time ago in an Elektor Electronics data sheet (May 1993) based on an SGS Thomson product announcement. Evidently SGS Thomson experienced difficulties in the development of this IC, since it took three full years until the IC appeared on the market. However, at the end of 1996 it was ready, and it was used in the 50-W A.F. Amplifier (November 1996 issue), which has been built by many hobbyists.
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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 its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1 = 390Ohm
R2,R5,R8 = 24kOhm
R3 = 19kOhm 6 (20kOhm )
R4 = 560Ohm
R6,R10 = 100kOhm
R7 = 2Ohm 2 2W
R9 = 47kOhm
C1 = 1µF MKT (lead pitch 5 or 7.5mm)
C2 = 470pF
C3,C4 = 100µF 25V radial
C5 = 100nF
C15 = 100nF (lead pitch 7.5mm)
C6 = 22pF
C7 = 47µF 50V radial
C9,C10 = 1000µF 63V radial (max. dia. 17 mm)
C11,C12 = 150nF (lead pitch 7.5mm)
C13,C14 = 10µF 63V radial
D1 = 1N4148
IC1 = TDA7293V (STMicroelectronics)
JP1 = 3-way pinheader *
JP2 = 2-way pinheader with jumper *
JP3 = 2-way pinheader *
K1,K2 = 10-way boxheader *
K3,K5 = 2-way PCB terminal block (lead pitch 5mm)
K4 = 3- way pinheader
K6 = 3- way PCB terminal block (lead pitch 5mm)
Heatsink *
Enclosure *
PCB, order code 010049-1
* see text
Power Supply
(depending on number of final amplifiers)
R1-R4 = 0Ohm 15 5W
R5,R6 = 4kOhm 7
R7 = 12kOhm
C1-C4 = 47nF ceramic
C5,C6,C11,C12 = 3µ F3 250VDC / 160VAC MKT (size 11x21x31.5mm) (e.g., Epcos B32524-Q3335-K, Farnell # 331-3311)
C7-C10 = 10,000 µ F 63V radial, lead pitch 10mm, max. dia. 45mm), PCB mount
D1-D4 = BYV29-200
D5 = high efficiency LED
K1-K10 = 2-way PCB terminal block (lead pitch 5mm)
Mains transformer, 2 x 22V at 225VA
PCB, order code 010049-2
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