It is worth calibrating your device in the soundcard preferences panel before commencing testing. You can perform a ‘loopback’ test to measure the harmonic distortion of your own audio interface by connecting an RCA cable between the output and input and using REW to generate a 1kHz tone (use the generator icon on the main window). UCA202 internal noise using laptop on battery UCA202 internal noise with laptop connected to AC power supplyĪs you can see from the above images, the UCA202 reports self-noise, and thus the noise floor is at about -130dBFS with a 50Hz spike and harmonics when connected to the mains supply. This window has it’s own options on the right hand side and the image below shows how I set mine up, along with the display of the UCA202 internal noise. From the main REW screen, click on the RTA icon to bring up the Real Time Analysis window.

Behringer UCA202 USB Audio InterfaceĪt this point, with only the interface connected to the PC (and possibly just running off the battery if you are using a laptop), you can check the internal noise of your device. A review including measurements of this interface by the respected engineer NwAvGuy shows that for the price, this is a reasonable piece of equipment. The choice of interface for me was simple as I already own an external soundcard, a Behringer UCA202, which can be bought for under £20. The input and output devices should be the sound card. Install the software and on the opening screen click on ‘preferences’ to configure your external interface once the device is connected to the laptop. Although the software is free, if you find it useful, please donate to the developer. The software, RoomEQWizard (REW), is primarily used for measuring and analysing room and loudspeaker responses, but it can also be used for measuring distortion in amplifiers. Rather than repeat everything that appears in that thread, I thought I would just outline the equipment and components I used and how I set it up. Essentially you can discover the harmonic distortion signature and the noise floor of your amplifier.Īs forum member XRK971 details in the first post in the thread, all that is needed at the most basic level is a decent internal PC sound card or external USB Audio interface, some free software, three resistors and some wire. I thought this level of analysis would be beyond my ability and budget, but an interesting thread appeared on recently, concerning a cheap method of measuring distortion. However, I am also curious about the objective measurements of the equipment. I imagine I am typical of many DIY audio enthusiasts in that I build something and hope that subjectively it sounds good.

How to distort audio