hifi engine

Realistic 31-1986 Updated Inside

Realistic 31-1986 Updated Inside

Here is Realistic 31-1986 showing inside after installation of Bypass switch, fuse with holder and boot. Three-prong grounded AC line cord was retrofitted as well. Notice black resistors are not stock, original 1/4-watt units (R109 and R110) were overheated. One-watt devices replaced stressed components. Long legged resistor near diodes was added for LED power. THD+N measurements yielded very respectable figures. This is a great Radio Shack version of an ADC Sound Shaper model.


Re: Realistic 31-1986 Updated Inside

Very nice...these old simple circuits often perform very well. The THD they do produce has a tendency to be low order since they run in class A. Even if the THD reached audible levels, it would provide a "warm" sound due to the low order nature. (Your speakers will have much more THD) Noise??? The 2SC1222 is a quiet device and as a guess from skimming what little useful data I can find on it, the noise in this would be comparable to a modern op amp and dominated by resistor noise as well as power supply noise. I actually like the single supply arrangement. So many things it seems that have dual supplies still have coupling capacitors. At least in this, they get a proper DC bias. In dual supply circuits they often get slight reverse bias and even get a shortened life.

Tuned inductors would be too expensive for today's stuff...