Monthly Archives

January 2017

Audio Theory

Understanding audio measurements: THD+N vs. amplitude and frequency

by nihtila January 8, 2017

written by nihtila

Presents the unwanted part of signal – something that was not put there and should not be there.
THD+N vs. amplitude graph is important as it reveals SNR, dynamic range, and THD+N ratio; all are expressed as ratio compared to a specified signal level.
The difference between THD+N level and THD+N ratio must be understood.
Signal level, signal frequency, and measurement bandwidth must be known (or guessed) when analysing results.

January 8, 2017 0 comment

Audio Theory

Understanding audio measurements: noise, SNR, and dynamic range

by nihtila January 8, 2017

written by nihtila

SNR is a ratio of two measurements, level and noise measurements, expressed in dB.
Signal level, measurement bandwidth, and weighting filter must be defined.
Dynamic range is like SNR but noise is measured in the presence of small signal; results should be the same.

January 8, 2017 0 comment

Audio Theory

DAC digital filters and their impact in time and frequency domains

by nihtila January 7, 2017

written by nihtila

Many DAC chips and devices using those chip have user selectable options for digital filter response to fine-tune tonal characteristics. I will take PCM1794A used on H-DAC as an example and see what effects these filter types have on impulse and frequency responses. This is just scratching the surface of the topic by briefly introducing some technical effects that can be measured. Tonal characteristics are not discussed here; those are highly subjective and a topic of another post (or debate).

January 7, 2017 1 comment

Obsolete PSU

Dual Trafo Board – Small dual transformer board

by nihtila January 1, 2017

written by nihtila

Placeholders for two small, approximately 10 VA, dual-secondary PCB transformers
- One transformer in series configuration for dual (analog) supply
- One transformer in parallel configuration for single (digital) supply
- Independent circuits, no common ground
- Supports the most common transformer pinouts
Fuses, rectifier bridges, and filtering capacitors

Dual Trafo provides three unregulated low power voltage rails for mixed signal devices, such as DACs. The board can be followed by a regulator board such as SmartPSU3 or SimplePSU3 (without filter capacitors) or it can be used to feed application board’s regulators.

January 1, 2017 0 comment

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