Top 5 Constraints: Amplifier

Aesthetics

Aesthetically, I’m not quite sure how to approach the project. The amplifier itself will be contained in an aluminum chassis, which I plan to sand and acid etch. Aiming for an industrial look, I want to contain the chassis inside a larger aluminum container of some sort rather than a classic wood cabinet. I’m planning on looking into aluminum sheet metal and fabricating my own cabinet, as that’ll probably yield the best results.

Price

With more advanced designs come more parts and a larger price tag. Essentially, I need to keep this design as simple as possible without skimping on the features I want to include. I already have some of the parts I need, including a working 12AX7, so savings can be had there.

As for using my available resources, I plan on fabricating the chassis at the ITLL and printing a PCB at the new Electronics Annex.

Output Power and Number of Valves

I want to keep this amplifier relatively simple with low output power, so a big consideration is the number and type of tubes used in its construction. With more tubes comes a more complicated design and a larger price tag, so I need to use as few tubes as possible. In the pre-amp stage, I plan on using two 12AX7 tubes, one to amplify each channel and the other to amplify the signal before and after the tone stack. As for the power stage, I plan on using a single EL84 tube in class A configuration, which should produce about 6 watts of output power.

As reference, I have a tube amplifier at home that outputs 60 watts. Due to the logarithmic nature of power output and sound generation from a speaker, multiplying the output wattage by 10 generally doubles the output volume. As such, this amplifier should be about half as loud as my current amplifier at full tilt.

Number and Complexity of Controls

Adding additional features may improve the quality of one’s design as well as its immediate usefulness, but with more features comes confusion. I want to design this amplifier to my own specifications, but it still needs to be understood and able to be operated by the common man. Furthermore, the control scheme must be aesthetically interesting but not indecipherable.

Size of Chassis

The size of the chassis directly corresponds to how complicated the control scheme can be, as well as how many additional quality-of-life improvements can be added. However, while a larger chassis will afford more controls, the overall footprint of the device increases and becomes bulkier and bulkier. Therefore, I need to find the best compromise between overall unit size and control/used space.