Project report

For this project, my partner and I will be following the signal flow of one of the microphone preamps that is currently non-functional on a USB Audio interface in reverse to determine where the signal path ends and begins. The interface is one that I have owned for several years, and the preamp randomly failed a few months ago. The ultimate goal we have is to follow the signal path and determine what is causing our preamp to fail and where along the signal path it is occurring.

In order to successfully follow the signal path to the preamp, we will first have to fully disassemble the outer case of the interface to allow us to access the internal PCBs. After this, we will have to follow the circuit traces connected to the preamp in question, and measure voltage and current values at various points along the trace trying to find any inconsistencies. Ultimately once an inconsistency is found we will have to remove the components directly connected to that point/s and replace them and repeat this process as needed until the signal is successfully outputted from the interface.

Access to a soldering iron, digital multimeter (DMM), replacement components, and possibly an oscilloscope and signal generator.

The only company that may technically be affected by this project is Steinberg Audio who made the actual interface itself. Since we are trying to repair this preamp on our own the company is losing a small amount of money that they would be earning for doing the repair themselves. Also, it is possible that we won’t be able to find the exact replacement parts we need and will end up either slightly degrade or improve the quality of the circuitry and components which could affect the company in the long run if I ever decide to resell this interface at some point.

So as briefly explained above my partner and I plan to disassemble the audio interface and then work backward through the signal path looking for any inconsistencies using our DMM. Once these have been found we will remove any components directly connected to points where inconsistencies were found using our soldering iron. We will also need to find and/or purchase any necessary replacement components. It may also be necessary to run a sine wave into the preamp and monitor the output until we get the desired results. This process may need to be repeated multiple times until the signal input and output are being transmitted properly.

Given that the semester is over in approximately 3 weeks from now, my partner and I will have to have at least 90% of the project done within the next 2 weeks, allowing the final week to be used for any last-minute modifications or fixes that may be necessary. This week we plan to measure voltage and current values at various points along the signal path looking for inconsistencies, and then remove the affected components as well as find and/or purchase any replacement components. The following week we will install our replacement components, reassemble the interface, and test the input again. If the issue still isn’t resolved, we will once again disassemble the interface and retest our affected points to determine where a problem still occurs and repeat as necessary until hopefully the preamp input functions properly.