Originally Posted by Arkku
Beautiful work, Ferrari. May I ask what kind of a circuit did you use for those analogue VU meters and where in the SOHA II's did you hook it up? I recently scavenged some vintage VU meters from an old tape deck someone was throwing away and I've been thinking of using them in a DIY project, perhaps even on my SOHA II, but I haven't figured out how it would be best to install them. Obviously I don't want them affecting the output quality.
To drive the analogue VU meters, I used the driver circuit as depicted below. The working of this driver circuit is very simple: the amplifier around T1 and T2 amplifies the line level signal to the desired level, the signal is then passing through the rectifier diodes D1 and D2. C4 smooth out the signal a bit before the signal is feeding to the VU meter.
Before use, an adjustment needs to be made.
Connect the circuit + VU meter to a function generator which output a 1KHz signal, ~300mV.
Dial P1 to its minimum (R=0), then dial P2 until the VU meter is reaching its maximum.
Next, turn P1 up until the VU meter is at ~ 50% of its total range (12 o’clock).
Depending on the level of the input signal (SACD player, DAC…), you might have to re-adjust P1 to get a proper reading of the VU meter.
For stereo application, 2 driver circuits are needed.