Meter mounting hole 38.5mm
Screw distance 32.5mm (center to center)
Screw hole inside diameter 3.3mm
Outside width 40mm
Meter height 31.5mm without meter connection mounts
Meter height 40mm including meter connection mounts
Yamamoto Shunt designed current meter, for tube autobias only
Please take a moment time, to understand those intelligent meters, because these are not like any other. When measuring the plate current of a tube, it is generally not desired that the signal path will go through the ampere meter. Reason is, that Ampere meter has a coil inside, and any Audio signals would be disturbed by this coil. The intention of these meters is to prevent frequency dependent effects, and other kind of interference. Besides not all low cost meters will indicate precise.
Yamamoto has found a nice solution for this. The meter is connected in parallel to the cathode resistor, and the meter is high impedance. This method is really genius. The meters gets a series resistor, which you can conveniently calculate.
What is also good to know, is by this method the meter has excellent short circuit protection. If by any mistake you make a short circuit, the cathode resistor will absorb the short circuit energy, not the meter
In series with the meter must be a resistor, to adapt for the value of the cathode resistor. This resistor is not be supplied with the meter, because the resistor value depends on the actual cathode resistor used. The resistor value is 100x the cathode resistor value, for the 100mA meter. (50x for the 50mA meter, 150x for the 150mA meter, and 300x for the 150mA meter.
The meters are extremely precise, and are more an "instrument" rather than just a meter only.
Another nice option is to use one meter, and just switch it from one channel to another, as done here with the flagship Yamamoto A06-02, the AD1 amplifier.
These are the bronze meter cover rings. The mounting holes are the same as for the meter. It is also possible to use the meter without the bronze cover rings. The meter by itself has a nice silver paint finish.
Bronze Meter Flange
The meter is pictured here with the mounting flange, but can be used also without. The advantage of the flange is you have no screws in the deck plate. For DIY, it is nice to know that the hole in the deck plate. can be made by hand, and with the flange still looks professional. However without flange will look very nice also.