DMP02 Power Amp

This is my first "serious" amplifier, built in 2002. 

Since then, it has been one of my favorite audio creations. It is nearly a true dual mono power amp, capable of delivering 2x100 Watts into 8 ohms. I write nearly, because a true dual mono has both of its circuit boards, or channels, separated. In my case, the left and right channel is sharing one PCB and one heat sink. Everything else is then following the path of a dual mono configuration. 

Each channel has its own over-rated voltage supply, with toroidal transformer, bridge rectifier and 8 Jamicon capacitors with 37600μF filter capacitance (a total of approx. 75200μF for both channels).

The over-rated system continues with 2 power bipolar transistors per channel, rated at 250 W each, manufactured by ON Semiconductor. 

The incoming signal is passively regulated by a 50kΩ stereo potentiometer. From here, it is fed to the driver stage, containing discrete transistors and WIMA foil capacitors. The focus of this design was simplicity - directing the audio signal only through necessary components in the amplification process.                                 

2022 update: 

As the Rotel power amp page suggests at the end, i planned to upgrade the chassis, feet and the connectors. I swapped the Rotel with this amp so i could listen to the music while i work on the Rotel upgrade. To my pleasant surprise,  this amp sounded more clear, with better detail and imaging. The soundstage was more focused and bass was not so heavy.  I quickly realized that this is the amp which truly deserves the upgrade...so hopefully, soon i will be able to finish the upgrade.

2024 update:  

What a ride...but the beast is finished. No, it did not take 2 years to upgrade it, however i do not remember how much time i spent on it. For example, the brightness of the three front LEDs took hours to adjust, so that the emitted light would not disturb me during the night hours and at the same time, would not be too weak during a bright sunny daylight.  

Now, if i tell someone that i enjoyed the amp transformation, i would lie, partially. There were times, when i thought about throwing the amp out of the window, but luckily, i did not do that : ) and now, i am even feeling proud of, what i have accomplished. 

I will start with the chassis that is completely new. It is made of a 0,8mm thick black painted steel plates, with the bottom one being reinforced by an aluminum U-shaped bar. For the chassis vibration control, i decided to use a butyl type suppressor - Evotec (it works perfectly, i highly recommend it).  

The main power switch (rocker type) is located in the middle of the bottom plate, 2 cm behind the wooden front panel. Between the wooden panel and the mains switch, right in the middle of those 2 centimeters, there is a downward facing orange LED, which indicates where the switch is located, as well as the amp being plugged to the AC power socket. This orange LED backlight cannot be turned of unless the AC power cable is unplugged from the AC socket. Because i love the look of a natural wood on any electronic equipment, i decided to use one of my favorite - the American walnut. The wood itself is not of the highest quality, because there are visible imperfections, but it gives an impression of being the most realistic piece of the tree, exactly as the nature made it. 

Except the AC cable socket and fuse holder, the rear panel contains the most necessary connections: 12V trigger, backlight switch, gold plated input RCA connectors and two pairs of insulated speaker binding posts.  Keeping the original idea of the simplistic design, not much of new features were added to the amp. Perhaps the biggest changes were done in its power supply and speaker switching possibility. 

The AC rocker switch is ON - OFF - ON type, so it is possible to turn the amp ON, without speakers being connected. This option makes the amp ready for performing its best job, since the transistors are in a semi-working temperature stage, while the speakers are disconnected. This stage is indicated by the white LED. Turning the switch to the other side tells the output relays to connect the speakers and turn-on the remaining two yellow LEDs. In this stage, the amp is fully performing its duty. 

The power supply section had been upgraded with vibration dampers under both toroid transformers and new PCBs for the rectifiers and power supply capacitors (Supertech 40000uF per channel).    

In the back left corner, a separate 12V transformer was added for the speaker protection board and other control relays.