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Audio Theory

Benefits of balanced headphones interconnection

by nihtila
written by nihtila
  • In balanced connection both speakers are individually connected to amplifier using two wires for each channel
  • Crosstalk can be improved by tens of dB by using balanced interconnection
  • Common-impedance coupling seriously limits crosstalk in conventional unbalanced headphones
  • Balanced output can be easily and cost-effectively added on designs; inverted signal is not required
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Audio Measurements

HP Buf improvements – 500 mW into 32 Ω headphones with 0.00015 % THD+N!

by nihtila
written by nihtila

HP Buf headphone amplifier’s already excellent THD+N figures can be pushed extremely low by replacing OPA2134s with LM4562s. This gives huge performance boost:

  • 5-8 dB lower noise floor, depending on gain setting
  • Up to 12 dB better THD+N
  • For example, THD+N at 100 mW into 32 Ω went down from 0.00065 % (-104 dB) to 0.00017 % (-115 dB)
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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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