UPSIDE - DOWN ASSEMBLY
The Model 1 printed circuit board (PCB) was designed with top to bottom symmetry. This symmetry enables building a tube amplifier with “tube audio look”, where tubes are mounted on top of the chassis. All parts, except tube sockets, can be mounted on the bottom of the board and soldered on the top side (top side is the one with component references in white silkscreen). That way, the PCB can be mounted close to the top of the chassis and tube sockets can be flush with the top, or even slightly higher, depending on your preferences. There are few things to keep in mind though:
-Top of the PCB should be at least ¼” below the chassis, to prevent metal chassis from shorting PCB circuits.
-PCB has a 1/8” hole underneath the sockets. Make sure to provide support to the PCB using the holes (in addition to the five mounting holes), to prevent board flexing and possible damage to the PCB when tubes are inserted or removed.
-You may find it convenient to use chassis mounted sockets, in which case there is no stress on the PCB during tubes insertion/removal. From the chassis mounted socket you can “drop” wires to the PCB. Be sure to use short insulated wires.
-If you mount headphones connector to the bottom of the board, left and right channel will swap. To bring everything back in order, you will need to swap inputs. Then your speakers will have left and right channel swapped. To rectify that, you will need to connect left speaker to the right channel and vice versa. Or, you can simply use a chassis mounted headphone jack and connect wires to the PCB in the right order.
-When the headphones/speakers selector switch is moved to the bottom, it will reverse the function – headphones position will turn the speakers on and vice versa. We do not think this is a major issue but you should be aware.
-If you move volume control potentiometers to the bottom of the PCB, the minimum volume position will become maximum. It may be cool, but it could also be annoying. The only solution to the problem is to use chassis mounted potentiometers and bring wires to the PCB.
-If you use chassis mounted parts (input jacks, headphone connector, switch and volume control, make sure to use short coaxial cables to minimize noise pickup and stray capacitances that may cause amplifier to oscillate.
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