This is the long delayed followup to the earlier post about power resistors as dummy loads and the nonlinearities found. After some further experimentation an 8 ohm load was built from four Riedon PF2270 series 2 ohm 200W thin film resistors (to give an 8 ohm load) and a surplus heatsink with fans. With 200W […]
As part of some ongoing work earlier this year I needed to test the performance of a high performance 200W/channel class D amp (more on the amp in some future post). To get accurate SNR and THD+N measurements a low pass filter is needed in front of the measurement system as the high frequency switching […]
This post is one of three related to the work done to measure resistor excess noise. A summary writeup and three other documents with experimental detail are provided to those interested in performing their own experiments. There is still ongoing work to test more parts, the revision currently posted is Rev 3.0
From the presentation at the Boston AES meeting held 27-Feb-18 at Shillman Hall, Northeastern University, Boston, MA. In addition to being a technical presentation aimed at anyone involved with audio, it also served as an example for students interested in submitting papers to upcoming AES events.
This page provides .WAV files that can be combined with audio tracks to perform your own evaluation of the audibility of noise, both the unavoidable white noise and the excess noise (mostly low frequency) that is present in differing amounts based on the resistor technology.
In the past only relative low power loads have been needed for the evaluation of monolithic class D amp chips as they are typically 25 watts and under. Now working with some 200W (8 ohms) – 400W (4 ohms) amps and beefier load resistors are needed. The following little parts are now on the bench:
As part of an ongoing investigation in to excess noise (also called 1/f noise) from resistors I recorded some data taken with the AP515 and posting it here. All 3 tracks have 80 dB of gain added to them using Audacity. The actual signal level from the resistor is a few microvolts. The part being […]