Posted 19th April 2013 at 10:24 PM byrjm Updated 20th April 2013 at 05:04 AM byrjm
Changed the collector load on the voltage amplifier stage to a current source (Q3), as per the Marantz SR2285B circuit.
Also increased the resistance of the feedback connection, R6+R8, there seemed to be no obvious advantage in making it much smaller than the typical load (>10k). The compensation capacitor C2 is increased to match, to flatten the HF response.
The circuit can drive light loads to +20 dB. Of course that's not much of a challenge for this general class of circuit.
I'm a bit stumped as to what the next logical step is from here. Seems to me to depend on what you actually want the circuit to do.
Holiday: Bad weather to a point it was near impossible to take a steady photograph due to the gusting winds. Hiding from the winds meant poor vantage points, very much non-idealistic for photographing landscapes.
Digi-key: The order turned up on the Monday morning, roughly 10 minutes before leaving. The PSU boards must have arrived mid week, a neighbour had those...
The parts order was enough components for one power supply and one amp. The PSU is assembled but untested as yet. The toroidal and 10K Alps RK27 are to be ordered from RS Components later today.
PCB issues: C1-C6... this is where trusting the people who generate default libraries for FreePCB falls down and my inexperience shows. Lead diameter on the caps is 28MIL, default part through-hole diameter is 28MIL... Each lead needed a quick file to reduce its width enough to fit the board. No other issues to report.
I don't think I could have made the overall size of the board...