In testing some of the A2B hardware what appeared to be high jitter on the clocks was observed. While specialized scopes & software are available for making jitter measurements one was not available at the time measurements were needed. The basic idea is simple enough – measure the clock edges and see if they are […]
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 […]
In a previous post a distortion producing alligator clip was unearthed. In this post high resistance test leads are discovered. These are generic banana plug to alligator clips (Vellman TLM3) that were purchased from Jameco: which are obvious generic made in China ones but from a reputable supplier versus the ebay/alibaba mystery stuff. Using them […]
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. These long form reports were summarized in to AES eBrief 486 (open access), presented at AES 145 (Oct 2018, NY, NY).
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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.
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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.
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Performing some tests on a prototype circuit with an Audio Precision AP515 it was noticed that a particular power resistor showed an unexpectedly high amount of distortion, almost 0.5% THD+N.
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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:
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