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Addon BalOut v2 – Balanced output board

by nihtila
written by nihtila
  • Simple balanced buffer with very high performance
  • Noise level: -117 dBV A-weighted (v2.0B)
  • THD+N ratio at 2 Vrms output signal: -119 dB (v2.0B)
  • Two versions can be populated:
    • v2.0A – traditional balanced output with inverted signal on cold lead
    • v2.0B – simplified output with ground on cold lead

Original Addon BalOut was designed for H-DAC but as there has been interest in those boards, this new version is easier to use in other applications:

  • No filter components
  • Normal opamps instead of fully differential opamp
  • Separete input signal pinheaders
  • Mounting holes
  • Reference designators on silk screen and cheaper 2-layer board
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Devices

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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Modular HP AmpObsolete

HP Buf – High-current buffered amplifier board for HP MoBo

by nihtila
written by nihtila

Amplifier daughterboard for HP MoBo modular headphone amplifier

  • High-power high-performance balanced headphone amplifier daughterboard for HP MoBo
  • Balanced input, balanced output
  • Jumper link for two gain options, default 0/10 dB
  • Jumper link for two output impedance options
  • OPA2134 opamps followed by BUF634 or LME49600 buffers
  • SNR: 113-121 dB A-w depending on the buffer, load, and gain
  • THD+N ratio at 100 mW (LME49600)
    • 300 Ω: 0.0004 % / -108 dB
    • 32 Ω: 0.0007 % / -103 dB
    • 16 Ω: 0.0012 % / -98 dB
  • Max power around 1 W (<0.1 % THD+N)
  • Update: get even higher performance with LM4562 opamps
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Modular HP AmpObsolete

HP TPA – Simple IC amplifier board for HP MoBo

by nihtila
written by nihtila

Amplifier daughterboard for HP MoBo modular headphone amplifier

  • TPA6120A2-based simple-IC headphone amplifier amplifier
  • Balanced input, balanced output
  • Jumper link for extra gain option; default 0/10 dB
  • SNR: 116-122 dB A-w depending on the gain and load combination
  • THD+N ratio at 100 mW
    • 300 Ω: 0.0015 % / -96 dB
    • 32 Ω: 0.006 % / -84 dB
    • 16 Ω: 0.009 % / -81 dB
  • Max power around 0.5 W (16 / 32 Ω)
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Modular HP AmpObsolete

HP MoBo – Modular headphone amplifier motherboard

by nihtila
written by nihtila

Motherboard for modular headphone amplifier system

  • Motherboard with inputs, outputs, power distribution, and signal routing for amplifier daughterboard
  • Balanced input
  • Balanced and unbalanced outputs
  • Output mute circuit
  • Requires separate amplifier board

HP MoBo is the basis of a modular headphone amplifier design. It provides input and output connections and simple power supply components (external power supply required), and connections for stackable amplifier daughterboard.

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H-DACObsolete

Addon H-MCU – Microcontroller addon for H-DAC

by nihtila
written by nihtila
  • Provides microcontroller interface to H-DAC jumper-link pinheader
  • Can be made Arduino-compatible with external USB-serial interface board

Addon H-MCU is designed to help use H-DAC in projects where I use microcontroller for selecting input and filter settings. It makes it possible to switch input and DAC filter with external remote signals.

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H-DACObsolete

Addon H-Filter – Simple through-hole balanced preamplifier addon for H-DAC

by nihtila
written by nihtila
  • High performance; H-DAC + H-Filter system performance measured with fixed resistors:
    • SNR: 119 dB (A-weighted)
    • THD+N ratio (1 kHz / 2 Vrms): -100 dB
    • Crosstalk: -112 dB at 1 kHz, -100 dB at 10 kHz
  • I/V-stage, filters, output stage, and opamps implemented with through-hole components for easy experimentations
  • Balanced outputs (XLR) on-board, uses unbalanced connectors (RCA) on H-DAC board
  • Potentiometer for volume control to transform H-DAC into preamplifier, or resistors for fixed output level
  • Takes voltage supplies and audio signals directly from H-DAC via pinheaders
  • 5×10 cm 2-layer PCB, through hole resistors and capacitors, placeholders for DIP8 sockets for opamps

Addon H-Filter is a simple filter and output addon for H-DAC with a possibility for a potentiometer to transform H-DAC into a preamplifier. In contrast with other designs of mine, it has been designed with through-hole components to allow easy experimentations with opamps and passive components. It offers high performance with low BOM cost and easy solderability.

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ObsoletePSU

Simple PSU 3 – 3-channel linear DC power supply

by nihtila
written by nihtila
  • Three linearly regulated voltage outputs
    • One dual supply for analog voltage supply
    • One single supply for digital voltage supply
    • Separate grounds
  • Fuses, rectifier bridges, filter capacitors, and regulator circuits
  • 2x LM317, LM337 (or any pin-compatible)

SimplePSU3 contains three simple 3-pin adjustable regulator circuits. Its one dual (analog) supply and one single (digital) supply suits especially well mixed signal audio circuits. Regulators are placed on the edge of the board for mounting on heatsink or chassis.

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ObsoletePSU

Smart PSU 3 – 3-channel linear DC power supply with monitors

by nihtila
written by nihtila
  • Three linearly regulated fixed outputs
    • One dual supply intended as analog supply
    • One single supply intended as digital supply
    • Common ground
  • Undervoltage, overcurrent, and overtemperature monitor and protection
  • Maximum 1 A per channel, depending on the design and cooling
  • Output relays
  • Software-controlled monitors (Arduino compatible)
    • Can also be used without microcontroller
  • 2x LT3081, LT3091, ATmega328P

SmartPSU3 provides three fixed relay-switched regulated and monitored low-power voltage outputs. As it has one positive and one dual positive/negative supply, it fits well for mixed signal audio applications, such as DACs, where dual analog supply and single digital supply are required. All channels use linear regulators for low-noise output.

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