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Electronic design and prototype development.

These are some selected examples of products, that I have been involved in designing, manufacturing or modifying for different manufacturers of consumer Hi-Fi equipment and High End Hi-Fi equipment.
The examples includes CD players, adc (analogue to digital converter), dac (digital to analogue converter) evaluation circuit, external clock input for CD player, integrated stereo amplifiers, active loudspeaker crossover network for laboratory use, class A active loudspeaker crossover network, 6 * 150 W power amplifier evaluation circuit, 2 * 100 W High End class A power amplifier, low cost universal power amplifier circuit, balanced preamplifier with MM/MC pick-up input.

CD player
Hi-Fi CD player
Hi-fi CD player with volume control, headphone output and remote control utilizing a low-cost mechanism.
This CD player has been in production in the Far East in a volume of 5000 units/year for some years and was updated mainly for cosmetic reasons, but a few bugs, that had been discovered through the years, were also fixed.
I have designed a new PCB and built and tested a prototype.
Due to better ground routing on the new PCB, the CD player's THD was reduced by 3 dB.
High performance Hi-Fi CD player
This CD player is designed around a Philips CD7 mechanism combined with a 24 bit D/A converter with class A analogue filters and balanced output stages.
Some key features are:
  • Discrete class A circuitry.
  • Unbalanced SPDIF and balanced AES/EBU digital outputs.
  • Unbalanced and balanced analogue outputs.
  • Separate power supplies for digital and analogue circuits.
  • 2nd. order harmonic distortion < 107 dB.
  • 3rd. order harmonic distortion < 114 dB.
I have designed the circuits and PCBs and manufactured and tested 4 prototypes.
D/A converter
Audio ADC/DAC test circuit
Test system for testing audio A/D and D/A converter modules at a hi-fi manufacturer's development laboratory. The board contains power supplies and logic for miscellaneous housekeeping signals.
High performance D/A converter for CD player
D/A converter with Pacific Microsonics HDCD decoder, Crystal Semiconductor 24 bit DAC, low-jitter crystal clock oscillator module and class A analogue stages for balanced and unbalanced outputs.
This DAC has a 2. harmonic distortion of -105 dB at 1 KHz full scale output and will drive 2.5 V peak into 50 ohms.
I have designed the circuit, PCB and built a prototype for evaluation by manufacturer.
External clock input for CD player
This small module, that can be installed in most CD players, allows the CD player's internal clock frequency to be synchronized to an external clock, so that digital data can be transferred to an external D/A converter without a sample rate converter. The module consists of a crystal clock oscillator, a PIC microcontroller and a PLL. The clock oscillator uses the crystal that was originally installed in the CD player to provide the clock when an external clock is not present. When an external clock is applied, the microcontroller calculates the ratio between the internal and the external clocks, programs the PLL dividers for this ratio and switches to the PLL clock.
I have designed the circuit, microcontroller code and PCB and made some prototypes for the manufacturer.
Integrated amplifier
2 * 20 W integrated amplifier
Low cost integrated amplifier with 5 line inputs, volume, balance and tone controls. This amplifier has been in production in the Far East in very high volumes for several years and was updated mainly for cosmetic reasons.
I have made a few circuit modifications, mainly to allow for the use of more modern components, and designed a new PCB, so the entire unit could be assembled without use of any wires.
2 * 150 W integrated amplifier
Integrated amplifier with 6 line inputs, volume, balance and tone control.
This is a combination of an existing pre-amplifier and power amplifier.
Some key features are:
  • Best value for money.
  • Remote control.
  • Motorized volume control.
  • Discrete only circuit.
The unit is produced in the Far east in a volume of 3000 units per year. Schematics for the existing products were available from the manufacturer.
I have finished circuit design, designed PCB and built and tested 2 prototypes.
Loudspeaker crossover network
High End class A loudspeaker crossover network
Active stereo 3 way crossover network.
Some key features are:
  • Discrete class A circuits.
  • No overall feedback except as required by the filters.
  • External power supplies for each channel.
I have designed circuits in cooperation with manufacturer, designed the PCBs, developed a PC controlled test procedure and tested 40 units.
Stereo 3 way loudspeaker crossover network experimental board
Experimental cross over network designed for use in a loudspeaker manufacturer's development laboratory. The crossover network's PCB is mounted on a 3 mm aluminum base plate and contains the power supply and amplifiers required to build a 2 channel 3 way 24 dB/oct crossover network. All filter components are mounted on solder pins to allow easy replacement.
I have designed the circuit, PCB and manufactured and tested 3 units.
6 * 150 W surround sound power amplifier
Surround sound amplifier in a 80 * 350 * 300 mm enclosure. The amplifier contain s 1200 W switch mode power supply for the 6 channels. Each channel has a separate signal controlled step down switch mode regulator to optimize the systems efficiency.
I have designed the circuits in cooperation with the manufacturer, designed the PCBs and built and tested a prototype.
2 * 100 W class A High End power amplifier
Discrete components only class A power amplifier with no global feedback.
Some key features are:
  • Discrete class A circuits.
  • No overall feedback.
  • Separate power supplies for each channel.
  • Separate, regulated power supplies for the voltage amplifier section.
  • Balanced and unbalanced inputs.
  • Continuous output power is 2 * 100 W into 8 ohms.
  • Continuous output power is 2 * 200 W into 4 ohms.
  • Dynamic output power is 2 * 1600 W into 0.5 ohms.
The audio circuits were designed by the manufacturer for best possible audio performance.
I have made some minor modifications to the audio circuits so they were easier to manufacture. I also designed the balanced input stage, the protection circuitry and the power supply regulators, designed the PCBs, developed a PC controlled test procedure and have tested 20 amplifiers.
Low cost universal power amplifier circuit
Universal power amplifier module that will operate with supply voltages from 30 V to 80 V. To lower the manufacturing cost, all components, except output transistors and driver transistors, are SMD types.
To simplify the module's integration in a product, short circuit protection, thermal protection and soft turn on is part of the module. Electrically the module's use is simplified by a 120 dB power supply rejection ratio and balanced input.
I have designed and tested the circuit.
Balanced preamplifier
Preamplifier with 7 balanced line inputs, 1 MM/MC pick-up input and 4 balanced outputs.
Separate buffers for each input provides a low drive impedance for the relay controlled signal source selector, so that a cross talk figure in excess of 120 dB can be achieved.
Some key features are:
  • Separate record source selector.
  • Electronically balanced line inputs.
  • 4 separate, transformer like, electronically balanced outputs.
  • Separate level adjustment for each input and output.
  • External power supply.
  • High power headphone amplifier.
  • Ultra low noise MM/MC pick-up input.
I have designed the circuits and the PCBs and manufactured and tested 2 prototypes.
Low cost preamplifier
Simple preamplifier with 6 line inputs, 1 MM/MC pick-up input and headphone output.
Some key features are:
  • Best value for money.
  • Remote control.
  • Motorized volume control.
The amplifier is produced in the Far East in a volume of 3000 units per year. A partial schematic were supplied by manufacturer. I have finished the circuit design, designed the PCB and built and tested 2 prototypes.
V Line
Product design
PCB lay-out
V Line
Hi-Fi products
PA products
Recording & studio equipment
Test & measurement equipment

Poul Petersen, C/Faya 14, 35120 Arguineguín, Las Palmas, Spain.
Tel/Fax: (+34) 928 152 807, Skype: poul.petersen.gc.
http://www.poulpetersen.dk, E-mail: pp@poulpetersen.dk
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