Shown on this  page is a custom modified Ming-Da 2A3 tube preamplifier. You will notice that many of the values have been blocked out. We do this to protect against copy cat modifiers.

The pictures show some of the upgrades made to the unit. For reasons mentioned about, we will not describe the actual circuit modifications made but can assure you that make a noticeable different both on the scope as well as to the ears.

 

 Before and After

Looking over these two pictures you can see all the areas that have been addressed and the circuit components that have been replaced and upgraded. What you cannot see in the pictures are the circuit modifications that allow this circuit to behave more properly.

BEFORE

AFTER

 

* All electrolytic shunt capacitors throughout the circuit replaced with metallized polypropylene pieces.
 

* Main power supply capacitors replaced with much better quality pieces and some bypassed with high value metallized polypropylene pieces.

* New DC filament supplies were built using Ultra Fast - Soft Recovery diodes replacing the cheap silicon pieces.

* This photo taken prior to modification shows the stock power supply capacitors as well as the stock silicon rectifying bridges used on the filament supplies.

 

* VH Audio V-Cap TFTF (Teflon) capacitors used in the coupling position. Due to the large physical size of these capacitors, custom mounting rails were built and installed.

* The red dots indicate areas that were addressed. The internal signal wiring (seen in white covering to the left side of the chassis) is a very high grade OCC with natural, unbleached cotton insulation.