Chinese version of Graphics Equalizer

I found nice VFD display on one 5.1 surround sub-woofer. It was quite big, powerful sound system with some indicator to display signal spectrum. I removed indicator and become suspicious- the device was too simple to be real. After looking to VFD without color cover, I discovered that it is just cheap Chinese imitation. From the first sight it looks like real device:


But if you look to VFD, you can find that indication elements are connected in strange way- the spectrum of the signal is hard-coded to VFD:

VFD hardcoded spectrum

The PCB is very simple- only three LM324 quad operational amplifiers and bunch of resistors. Theoretically it can generate 12 levels of indication, but VFD is only with 9 anodes. Schematics are typical- comparaison of input signal with voltage divided by resistor network. When I feed-ed DC signal to the input I received nice “spectrum” of it.

VFD in action

Also, I like the mystic word “REVEL”. It looks like some “right” version of word “LEVEL”. This is nice illustration of Chinese-English vocabulary.

Next time, buying “cool” surround speaker system, be careful.

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