Old Projects

I have listed these audio projects as ‘old’, compared to ‘new’ projects page. Time-wise the difference is not significant but I feel a lot has happened in my way of doing things.

My newer projects are better thought through, designed, and tested. They contain more information regarding the design and chosen approaches, what could have been done differently, documentation is better quality, and rather comprehensive measurements and test results are provided.

These older projects were carried out with a more straightforward manner – I designed something, build it, tried it, and if everything worked ‘well enough’, that was pretty much it. I also did not have access to state-of-the-art measurement equipment.

All of them have been working and been in use at least for a while. I do not have all of them anymore. I am planning to update the 4-channel system to have newer better boards including all relevant measurements.


4-Channel DSP-DAC-Preamp-PowerAmp System

  • This system consists of the 4 following projects
    • SharcDSP
    • Quad DAC
    • Quad Preamp
    • Hypex Power Amplifier

SharcDSP – 8-Channel Digital Signal Processor

  • 6 digital stereo inputs: 2 toslinks, 2 coaxial RCAs, 1 coaxial BNC and AES/EBU (XLR)
  • 4 coaxial BNC stereo outputs offering 8-channel output where channels are mixed/filtered from two input channels
  • All electrical connectors are transformer-isolated
  • Can be used for crossover filtering for multi-way active speakers, parametric equalisation, digital room correction; filters are given in parameters (PEQ), biquads and/or FIR coefficients; also includes level, delay, polarity, compressor/limiter
  • DSP-solution from miniDSP: miniSHARC OEM/DIY-board and miniSHARC plugin software; CS8406 SPDIF-transmitters

Quad DAC – 4-Channel DA-Converter

  • 4-Channel 192 kHz / 24-bit DAC
  • Two transformer-isolated 4-channel digital inputs: coaxial BNCs and RCAs
  • Balanced and unbalanced analog outputs
  • Wired remote control interface with Quad Preamp
  • PCM1794A DACs, OPA2134/LME49724 op-amps, CS8416 SPDIF-receiver

Quad Preamp – 4-Channel Analog Preamplifier

  • Three 4-channel inputs: two balanced and one unbalanced
  • Balanced and unbalanced outputs
  • Comprehensive software features
  • Remote control possibility with any IR-remote control using NEC codes
  • Controls whole system using wired remote control interface to SharcDSP and Quad DAC
  • PGA2310 volume control, THAT1200 balanced receivers, DRV135 balanced drivers, OPA213 op-amps

Hypex Power Amplifier

  • 2x Hypex UcD180HG HxR audio amplifier modules delivering 2x 180 W @ 4 Ω or 2x 120 W @ 8 Ω
  • Hypex SMPS400A180 switched mode power supply designed for UcD180s with power rating of 400 W

HP DAC – Headphone Amplifier DAC

  • Compact audio digital-to-analog converter and headphone amplifier
  • 2 digital SPDIF stereo inputs: toslink and coaxial (isolated)
  • Analog unbalanced RCA outputs
  • PCM1794A DAC, OPA2134 and LME49724 op-amps
  • TPA6120 headphone amplifier with PGA4311 volume control
  • Powered by wall-wart type AC-adapter

miniD Preamp – Tiny miniDSP-based 4-Channel Preamplifier

  • Very small 4-channel preamplifier with digital signal processor and digital-to-analog converter
  • 4 digital SPDIF stereo inputs and one analog input
  • 4-channel unbalanced analog output
  • DSP-solution consists of miniDSP-board and applicable software
  • Extensive software features: IR-remote code learning, input-/output-wise volume offset and channel balance, input renaming
  • Main components: SRC4392 SPDIF-receiver and sample rate converter, miniDSP-board, PCM4104 DAC, OPA1662 op-amps and PGA4311 volume control

DD Preamp – Compact 4-Channel DSP-DAC-Preamplifier

  • All-in-one compact audio solution including digital signal processor, digital-to-analog-converter and preamplifier
  • 4 digital SPDIF stereo inputs: 2 toslink and 2 coaxial (isolated)
  • 4-channel analog balanced outputs for main speakers and subwoofer(s)
  • Output channels can be independently mixed from input channels, added with versatile filtering options for digital room correction or crossover filters
  • Main components: ADI ADSP21369 based miniSHARC DSP-kit, PCM1792A DACs, OPA2134/LME49724 opamps, PGA4311 volume control and FreeRTOS-based software running on ATmega324A to control everything
  • Extensive software features: IR-remote code learning, selectable DSP-preset, input-/output-wise volume offset and channel balance, DAC filter steepness, input renaming

Boombox Mini – Battery Powered Picnic Speaker

  • Battery powered small and lightweight speaker with long playing time
  • 3,5 mm plug and bluetooth for connecting music source
  • Mostly existing components used – rather cheap and quick to build
  • Audio Pro stage 22, 41Hz AMP32-PS class D amplifier, 12 V 3,2 Ah gel battery

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