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USBHI – USB-interface for headset

by nihtila
written by nihtila

Simple USB audio interface for headset

  • Based on PCM2912A reference design; single IC providing:
    • USB-interface
    • 2-channel DAC and headphone amplifier
    • 1-channel ADC and microphone bias
  • TRRS jack for headset, or headphones and microphone can be wired out separately
    • CTIA or OMTP type jack can be selected with jumper link
  • Not for higher end audio but perfectly adequate for gaming, podcasts, calls, etc.
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DevicesObsolete

miniD Preamp – Tiny miniDSP-based 4-Channel Preamplifier

by nihtila
written by nihtila

This is an updated version of my old miniD preamp from 2014 combining miniDSP and 4-channel DAC-preamplifier

  • Small 4-channel preamplifier with digital signal processor and digital-to-analog converter
    • DSP can be used for crossover for 2-way speaker or between speaker and subwoofer, and/or digital room correction
  • 4 digital SPDIF stereo inputs and one analog input
  • 4-channel unbalanced analog output
  • DSP-solution consists of ADAU1701-based miniDSP-board and applicable software
  • Atmel AVR-based firmware with extensive features such as IR-remote, balance, offset for inputs and outputs, DSP bypass, selection between analog or digital volume control, etc.
  • Main components: SRC4392 SPDIF-receiver and sample rate converter, miniDSP-board, PCM4104 DAC, OPA1662 op-amps and PGA4311 volume control
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DevicesObsolete

HP Pre 2016 – DAC-preamplifier with headphone amplifier

by nihtila
written by nihtila
  • H-DAC and Addon H-PreAmp encased and used along with PSU Pre 2016 external power supply
  • Very high performance DAC-preamplifier with headphone amplifier
  • Compact and simplified design yet extensive list of features
    • Coaxial, optical, and USB inputs
    • DAC filter response switch
    • Balanced (XLR) and unbalanced (RCA) outputs, approximately 2 Vrms output level
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PSU Pre 2016 – External power supply for DAC-preamplifier

by nihtila
written by nihtila
  • Dual Trafo Board and SmartPSU3 modules
  • Two 3-channel power outputs for DAC-preamplifiers, total current capability being approximately:
    • +14 V, 250 mA
    • -14 V, 250 mA
    • +7 V, 500 mA
  • Over-current, under-voltage, and over-temperature protection provided by SmartPSU3
    • Error codes blinked by the front LED

This is the device where Dual Trafo Board and SmartPSU3 were originally designed for – external power supply that is simple yet provides some protection in case something goes wrong in the target device. Its current output capabilities are somewhat limited but enough for small DAC and preamplifier. It was designed for HP Pre 2016 although headphone output power may be somewhat restricted with this power supply.

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SharcDSP – miniSHARC-based 8-Channel Digital Signal Processor

by nihtila
written by nihtila

Digital signal processor designed for my 4-channel DIY system.

  • 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; outputs with CS8406

Note that this is one of my “old” projects and is kind of obsolete. I do have bare PCBs if someone wants but I have no intentions to further develop the design, documentation, or measurements, which are not really comprehensive. However, the device was fully functional so feel free to pick tips for your own implementation.

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