# Precision Analog VU-meter Circuit

Posted on May 5, 2017

The vu-meter is distinguished in two categories, those with the needle instruments and those with the led column. Whether it is a tube amplifier or integrated amplifier, a vu-meter sound level meter is required. Today there are enough chips that do this work by using led to indicate the sound level. However, the amplifiers with LEDs are a retro version and consequently the indication of the led sound level would probably not fit in this case. While an analogue display circuit would fit perfectly. The circuit is steady, reliable, fast in response (depending of course on the inertia of the instrument) and is visually suited to tube amplifiers.

## The virtual circuit

The theoretical circuit of the structure is made up of two identical circuits based on a power amplifier that covers each channel. Each channel is an amplifier. At its exit we have connected a micro-ammeter via a bridge, which gives the sound level to each channel. The bridge rectifies the alternating current and the capacitor present at each output increases the inertia of the instrument. At the input of each operator there is one trimer to regulate the sensitivity of each channel. The diodes that are wired, back to back, due to their linear function, create a logarithmic response to the characteristic transfer of each operator.

## Construction

The construction does not show any critical points. All materials are placed on the board designed for this purpose. Start building by first attaching the resistors and the connection to the power supply and other external connections and finish with the unique integrated construction.

Allow the materials to be polished to prevent them from sticking upside down. When finished, connect the voltage and signal the corresponding inputs of the construction. With the trimers that exist, adjust the instruments so that there is no indication in the absence of a signal.

Electronic Components Needed
R1: 120KΩ
R2: 100KΩ TRIMMER
R3: 100KΩ
R4: 560Ω
R5: 120KΩ
R6: 100KΩ
R7: 100KΩ
R8: 560Ω
C1: 1μF
C2: 1 μF
C3: 10μF
C4: 33μF
C5: 1μF
C6: 1μF
C7: 10μF
C8: 33μF
D1: 4 X 1N4148
D2: OA85
D3: OA85
D4: 4 X 1N4148
D5: OA85
D6: OA85
IC1: TL082

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Spyridon Giomataris   Apr 23, 2021

There are 2 capacitors 100uF on the circuit board which are not listed in the spare parts list!

Dihan   Apr 19, 2021

Nice circuit.... but how do you calibrate it?

Spyridon Giomataris   Apr 13, 2021

The schematic differs from the pcb. For examble the OA5 are connected to the trimmer center tap via a cap 1uF. On the pcb the diodes are connected to the center tap without the cap! there is no 10uF capacitor. The 120K is a 100K. The 10uF cap is an 100uF cap.Many inconsistencies and different connection between the schematic and the pcb.Are you sure that both the schematic and the pcb are identical or have been modified by someone else??Thanks

good   Sep 2, 2020

Nice analog vu meter

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