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Like HH1, the purpose of HH2 is as a learning platform. HH1 covered PI basics with every parameter adjustable. HH2 covers PIC programming with most parameters fixed in code.
HH2 also has some design changes that allow more experimentation with fast sampling. The coil switch driver is now a much faster push-pull circuit. The coil switch has a drain diode added. The preamp is now a 2-stage design, and includes room for a feedback clamping diode.
A number of people have expressed a desire to learn micro programming, so the main feature of HH2 is the PIC12F683 micro. This controls all of the timing and offers the ability to generate the audio response and to even directly sample the preamp output and do all processing digitally. Admittedly, the PIC's internal ADC is only 10 bits and is probably not sufficient to get good performance, but it's good enough for learning code techniques.
As with HH1, raw performance is not the main focus of HH2. The overall architecture is fairly vanilla PI, and can be made to perform on par with the Surfmaster PI.
- Carl
HH2 also has some design changes that allow more experimentation with fast sampling. The coil switch driver is now a much faster push-pull circuit. The coil switch has a drain diode added. The preamp is now a 2-stage design, and includes room for a feedback clamping diode.
A number of people have expressed a desire to learn micro programming, so the main feature of HH2 is the PIC12F683 micro. This controls all of the timing and offers the ability to generate the audio response and to even directly sample the preamp output and do all processing digitally. Admittedly, the PIC's internal ADC is only 10 bits and is probably not sufficient to get good performance, but it's good enough for learning code techniques.
As with HH1, raw performance is not the main focus of HH2. The overall architecture is fairly vanilla PI, and can be made to perform on par with the Surfmaster PI.
- Carl
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