For sale the developed pcb only for marantz model-250M amplifier (!!!). These are logarithmic output power level indicator amplifier. (Attention this is not checked, this pcb may also be suitable for marantz model 250 amplifier).
Sold only PCB, no indicators (!!!). See please first and second picture. The other photo is an example of how it looks live.
Schema with TA7318 standard, two-way power supply that is taken from the common power supply. No secrets. Some amplifiers use separate chips for each channel. What an engineering idea, I don’t know. This can be done here as well.
As the existing switches that switch the sensitivity of the indicators become meaningless, logarithmic sound potentiometers are installed instead (100k). This is very good. The original engineering idea is imperfect: leaving the entrance to a rather powerful amplifier open.
Attention, the previous drawing of the indicators scale no longer makes sense because it no longer corresponds to the markings as provided in the marantz 250m service description. In this case, it is planned to use the full power of the amplifier (f1000hz, 30.00V ~ 124W / 8ohm load) with the indicator tilting to the right to +3.
E.g.: 0.89V, ~ 0.1W will show you half way between -5 and -3. (picture 7 and 8).
There are other possible adjustment options. It’s already a matter of your imagination! Note, is two possible options to connect the indicators. You will need a solder jumper (the third picture).
Questions are available privately by email