Work continues on refining the B17-B bass amplifier. The intent is to make this a fairly lightweight portable unit that can be used at least in smaller venues to substitute for heavier equipment. Some of the features to help with this:
- Use of a switching power supply for the high current output stage
- The second stage of the tube preamp is biased to begin tube compression at higher volume levels, to give it that “tube sound”
- By continuing to increase the level beyond where tube compression kicks in, it will enter solid-state clipping if additional harmonics are desired.
Here is the latest circuit. By adjusting the value of R8 we can vary the onset of tube compression. By varying R19 we can determine how hard the output stage is driven and thus the onset of solid-state clipping.
The HV (High Voltage) supply is shown below.
The V+ Supply will be a TKD-Lambda LS15048 switching supply.
More simulation and calculation is required before component selection is confirmed, but this circuit is getting close to being a buildable prototype.