Step 3: Time to Wire.
Time to wire. I am assuming that you are capable of reading a schematic and then knowing how to wire it. This circuit is easily made possible point-to-point. I debated with the idea of printing a circuit board or using proto board. However, after I built the circuit on breadboard, I realized how finicky the circuit could be. For instance, if a specific wire were too long or in close proximity with another wire weird stuff would happen. For instance I was able to pickup a radio station! Thankfully it was nice smooth jazz. But more commonly I would get humming in one or both channels. It took some time but I finally found the perfect layout for total silence from the circuit in my enclosure.
Some tips include:
• Braid or twist your input cables off of the RCA inputs. Braiding/twisting helps to eliminate any RF interference.
• Braid your LED runs into the tube sockets. For some reason the negative lead picked up some RF interference when near the tubes. Braiding the leads solved this issue.
• Check for shorts. A couple of times I fired up the amp in the preliminary phases and I would get clicking or dead silence. It was a short every time. One loose strand of braided cooper wire touching a resistor or something stupid. More than likely the error is human, the chances of a failed resistor or MOSFET are incredibly low.
• Use the optional resistors from the Dsavitsk schematic; they help eliminate humming and background noise.
• Lastly, keep your runs as short as possible. Audio circuits are finicky.
So, is the heat sink really necessary? Yes, the MOSFETs melted my plastic breadboard after less than a minute of use. Those guys get hot. You don’t want to melt your MOSFETs and risk destroying your circuit.
The added LED’s were a must for me. I love the way that they look. The tubes do glow, however they’re hardly noticeable unless you’re looking for the filament. Plus the LED’s allow seeing if the circuit is on/off. I also added an additional switch just to turn the LED’s off and on. If you are wiring in the LED’s, make sure to use a resistor rated for the voltage drop. The power supply is 48v, that’s a big drop down to 3v to power the LED’s. The resistor needs to be able to dissipate that wattage. Use a resistor calculator to calculate the wattage rating needed for your resistor (http://led.linear1.org/led.wiz). I used a resistor rated for 2 watts, well above what should be required.