- Written by Dr. David A. Rich
- Published on 23 September 2013
- AVR - Audio Video Receiver - Build Quality: Part I
- Page 2: Understanding DAC Specifications
- Page 3: Digital Reconstruction Filter
- Page 4: Number of DACs per Chip
- Page 5: Improved Distortion and Noise Performance with Balanced DAC Output
- Page 6: Enhanced Distortion Performance with Current Mode DACs
- Page 7: Multiple DACs Combined to Produce a Single Channel
- Page 8: Chart Presenting Build DACs used in AVRs Across Manufacturers and Price
- Page 9: The Right Side of the Chart: More Details about the AVRs and Pre/Pros
- Page 10: The concept of Effective Bits
- Page 11: Single Chip Analog AVR LSI
- Page 12: Enhanced Performance with SSI Parts
- Page 13: Limitations of Operational Amplifier Performance with the Single Chip Analog AVR LSI
- Page 14: Limitations on the Performance of Semiconductor Switches with the Single-Chip Analog AVR LSI
- Page 15: Use of Relays to Achieve Better Performance
- Page 16: A Very Brief Look at Changes in Power Amps in AVRs
- Page 17: Conclusions
- All Pages
Enhanced Performance with SSI Parts
Previously, a single chip analog AVR LSI was associated with lower priced AVRs. In contrast, higher-priced units would use Small Scale Integrated circuits (SSI) to provided performance advantages.
An opamp is an SSI chip. Opamp packages separately contain as many as four units.
To form the electronic volume control, an SSI part containing only resistor strings and switches is used. External opamps are added to form the complete circuit.
The switches are grouped in SSI packages with 4 – 50 switches pairs per package. Multiple switch packages are dispersed throughout the AVR to perform functions such as stereo analog input selection and signal routing to the electronic volume controls.
One downside of some AVRs built with SSI chips is the latitude afforded to the designer to incorporate extra functions to the analog path. This is most common in top-of-the-line Japanese designs using SSI chips. Additions, such as analog bass management high-pass filters, analog tone controls, and analog down mix add solid state switches and extra opamps to the main signal path even when the functions are bypassed. The additional components reduce channel separation and can increase distortion.
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