Discussion Overview
The discussion revolves around the design of a DC filter intended to remove noise from an amplifier circuit, specifically addressing the challenges of calculating the necessary inductance for the filter. Participants explore the potential sources of noise, including 60Hz hum, and consider various components and configurations for the filter.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Experimental/applied
Main Points Raised
- One participant seeks guidance on calculating the inductance needed for a DC filter to eliminate noise, mentioning a DC power input of 16V @ 4A and a DC resistance of 4 Ohms.
- Questions are raised about the quality factor (Q) at frequency and self-resonant frequency, with a preference for using a ferrite core for the inductor.
- Another participant asks for more information about the system to better understand the source of the 60Hz noise, suggesting it could be due to ripple from the input bridge rectifier or interference from AC-powered devices.
- A participant reflects on the possibility of the noise being related to grounding issues, despite uncertainty about how that would affect the circuit.
- There is mention of a voltage ripple rejection pin on the OPAmp, with a participant questioning its typical connection and expressing confusion over its relevance.
- One participant reports experimenting with grounding the ripple rejection pin, which resulted in audio issues, and notes that the hum was only present on one channel.
- Plans are shared to test a different DC-powered audio source to determine if it reduces noise, with speculation that the noise may originate from the internal DC rectifier of the current radio being used.
Areas of Agreement / Disagreement
Participants express differing views on the source of the noise and the effectiveness of filtering solutions. There is no consensus on the best approach to resolve the noise issue, and multiple hypotheses about its origin remain under discussion.
Contextual Notes
Participants have not fully defined the assumptions regarding the noise source, and there are unresolved questions about the specific characteristics of the filter components needed for effective noise reduction.