EP#145: The Vox in a Box Roxs
Circuit Break - A MacroFab Podcast6 Nov 2018

EP#145: The Vox in a Box Roxs

  • 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

Episoder(448)

EP#40: Update on the MacroDuino and FX DEV Board

EP#40: Update on the MacroDuino and FX DEV Board

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EP#39: Maniacal Moving

EP#39: Maniacal Moving

Podcast NotesAs mentioned in last weeks episode, MacroFab is moving to a new location currently. See Figure 1.Parker is going to hack his Jeep's radio this weekend with a Bluetooth Audio board. Parker...

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EP#38: Trey German Returns and Automatic Game Overs

EP#38: Trey German Returns and Automatic Game Overs

Podcast NotesTrey German is back to give an update on completing the epic Icarus Trophy race. See Figure 1,2,3,4. Trey was previously on MEP EP#10: IoT's Cloudy Future.The Icarus Trophy race is a 1000...

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EP#37: Banned Arduinos and Tuning Software By Ear

EP#37: Banned Arduinos and Tuning Software By Ear

Podcast NotesMacroFab is moving soon. Fun times! See Figure 1 to see all the stuff we need to move.Parker has finished the first version of the Selective Solder Fixture. It uses magnets to support the...

14 Okt 201630min

EP#36: Cloud Net

EP#36: Cloud Net

Podcast NotesFirst podcast and the first recording in the "Bomb Shelter" (name pending). See Figure 1.Parker is working on an adjustable fixture to work along with the Jig Of Destiny that is currently...

7 Okt 201630min

EP#35: Surgical Synthesizers

EP#35: Surgical Synthesizers

Podcast NotesParker got the bootloader on the  EFM8 working. The  Errata shows that EFM8 chips younger then data code 1601 do not have a working bootloader. Should have an article out next week about ...

30 Sep 201635min

EP#34: Ghost Hunting with Centex Paranormal

EP#34: Ghost Hunting with Centex Paranormal

Podcast NotesMichael Lyons of Centex Paranormal pays us a visit. Centex Paranormal is based out of Austin, Texas. They design ghost hunting equipment. See Figure 1.New product out, EDI+. Has SD card d...

23 Sep 201628min

EP#33: The Macro Hour Mashup

EP#33: The Macro Hour Mashup

Podcast NotesCo-Podcast time with The Amp Hour's Chris Gammell.Parker finds new ICs through the subreddit /r/nicechips and subscribing to manufactures mailing lists.Chip manufactures should just adver...

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