- Stephen's Vox in a Box
- Preamp Design
- Vox AC30 preamp - 3 gain stages with a cathode follower and a phase inverter
- Phase inverter - create differential signals for the power amp input
- Drop signal using voltage dividers and mosfet buffers
- 320V phase inverter to 18V buffer drive
- Built point to point on an aluminum plate for easy modification and testing
- Power Amp Design
- TPA3116 Class D amplifier
- LM311 comparator mute circuit for start up mute ~5 to 10 Seconds
- Runs at 400KHz - Left open pads for boosting this up to 1.2MHz
- Is there an advantage at running at higher frequencies?
- Power Supply Design
- TPS40210 Switching controller into a diode/cap ladder voltage multiplier
- 7 stages of multiplication leads to ~50V per stage
- Variable Switching from 35KHz to 1000KHz
- PMP8621 Appnote
- Testing the Vox in a Box
- Been going nonstop for weeks now
- Have taken it up to nearly 60 Watts without problems
- Layout of the PCB
- Multiple ground system with master start
- Each sub circuit has its own ground return
- 8 Master star ground returns
- 4 layers
- Issues with the current design
- High Voltage SMPS does not like high capacitive load
- Ground for signal input is very important - Nearly all noise is dominated by this single point
- Alligator clips for signal patching are not low noise…
- Cold Heater impedance
- Current Schematic for the Vox in a Box
- Fusion 360
- New amp design
- Learning by building a virtual amp
- Vox in a box
- Going to model the whole design to ensure proper fit
- R.F.O.
Tags: Chris Gammel, electronics podcast, Fusion 360, Hackaday, LM311, MacroFab, macrofab engineering podcast, MEP, PMP8621, Preamp, SuperCon, TPA3116, TPS40210, Vox AC30, Vox in a Box
