Sales

Weekdays:
8:30 AM- 5:30 PM CDT

832-564-0638

Support

Weekdays:
8:30 AM- 5:30 PM CDT

832-924-0146

The vox in a box roxs

MacroFab Engineering Podcast #145

The Vox in a Box Roxs

Related Topics
Breadboarding for Success

This week we are talking about Breadboards. Is breadboarding a circuit or design still applicable in today's SMT component dominated world?

Datasheet Lore

What lore have you discovered in component datasheets? On this episode, Parker talks about how he picks electrical components and risk management.

The PCB Plague

Ever have PCBs that solder just will not wet and solder to? You probably thought it was improper soldering technique but that was probably not it!

Other Resources

MacroFab Engineering Podcast
Blog
eBooks & Guides
Webinars
Videos
Case Studies
MacroFab Platform Help

November 7, 2018, Episode #145

Stephen gives an in depth update to his Vox in a Box project! 100 Watts of Class D amplification!

Podcast Notes

  • 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.

Visit our Slack Channel and join the conversation in between episodes and please review us, wherever you listen (PodcastAddict, iTunes). It helps this show stay visible and helps new listeners find us.

Vox in a Box Schematic – Page 1

Vox in a Box Schematic – Page 1

Vox in a Box Schematic – Page 2

Vox in a Box Schematic – Page 2

Vox in a Box Schematic – Page 3

Vox in a Box Schematic – Page 3

The Vox in a Box driving the VOX AC30 Tube preamp and speakers!

The Vox in a Box driving the VOX AC30 Tube preamp and speakers!

Stephen has also been modeling parts in electronics in Fusion 360!

Stephen has also been modeling parts in electronics in Fusion 360!

About the Hosts

Parker dillmann
  Parker Dillmann

Parker is an Electrical Engineer with backgrounds in Embedded System Design and Digital Signal Processing. He got his start in 2005 by hacking Nintendo consoles into portable gaming units. The following year he designed and produced an Atari 2600 video mod to allow the Atari to display a crisp, RF fuzz free picture on newer TVs. Over a thousand Atari video mods where produced by Parker from 2006 to 2011 and the mod is still made by other enthusiasts in the Atari community.

In 2006, Parker enrolled at The University of Texas at Austin as a Petroleum Engineer. After realizing electronics was his passion he switched majors in 2007 to Electrical and Computer Engineering. Following his previous background in making the Atari 2600 video mod, Parker decided to take more board layout classes and circuit design classes. Other areas of study include robotics, microcontroller theory and design, FPGA development with VHDL and Verilog, and image and signal processing with DSPs. In 2010, Parker won a Ti sponsored Launchpad programming and design contest that was held by the IEEE CS chapter at the University. Parker graduated with a BS in Electrical and Computer Engineering in the Spring of 2012.

In the Summer of 2012, Parker was hired on as an Electrical Engineer at Dynamic Perception to design and prototype new electronic products. Here, Parker learned about full product development cycles and honed his board layout skills. Seeing the difficulties in managing operations and FCC/CE compliance testing, Parker thought there had to be a better way for small electronic companies to get their product out in customer's hands.

Parker also runs the blog, longhornengineer.com, where he posts his personal projects, technical guides, and appnotes about board layout design and components.

Stephen Kraig
  Stephen Kraig

Stephen Kraig began his electronics career by building musical oriented circuits in 2003. Stephen is an avid guitar player and, in his down time, manufactures audio electronics including guitar amplifiers, pedals, and pro audio gear. Stephen graduated with a BS in Electrical Engineering from Texas A&M University.

Special thanks to whixr over at Tymkrs for the intro and outro!

Related Podcasts

MEP 299 FI

Operation Scope Creep

Multi-layer PCB designs. As an engineer, how do you decide when it is time to increase layer count and how do you decide what goes on those layers?

Design for everything

Design For Everything

DFM, DFT, DFA? What does it all mean to product designers and engineers? Stephen and Parker cover what Designing For really means.

Datasheet lore

Datasheet Lore

What lore have you discovered in component datasheets? On this episode, Parker talks about how he picks electrical components and risk management.

Breadboarding for success

Breadboarding for Success

This week we are talking about Breadboards. Is breadboarding a circuit or design still applicable in today's SMT component dominated world?

The pcb plague

The PCB Plague

Ever have PCBs that solder just will not wet and solder to? You probably thought it was improper soldering technique but that was probably not it!

We have clearance clarence

We Have Clearance, Clarence

On this episode, there are some AND!XOR hints for DC29 and we discuss the difference between PCB DRC specifications for clearance and creepage.