Last year and this spring I spent a lot of free-time on DIY electronics and as my full-time job is also electronics related, I needed to take a few-month break. I just didn’t feel interested, inspired, or motivated anymore. During the time off I focused a bit more on my photography hobby. I hoped that after a break I would feel motivated to do more electronics again. While even I had my doubts, the inspiration is back! I am designing new boards again. There will be a new DAC plus addon boards; the design and ideas are based on the H-DAC. I will also try to make assembled boards available to buy at some point.
Author
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
Easy and quick way to check new footprints, that you definitely read all datasheet measures correctly when drawing the footprint, is to print the layout on paper and fit components on it.
- 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
- 6-channel analog output module for Roland MV-8000/8800; mimics analog part of Roland MV8-OP1 module
- Digital signal and supply connector with identical pinout to the original
- Same output level as the original
- High performance
- SNR: 118 dB (A-weighted)
- THD+N ratio: -103 dB min, -93 dB max
- Crosstalk: -112 dB max
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.
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)
- Modular headphone amplifier based on HP MoBo motherboard and changeable amplifier daughterboards:
- Balanced input
- Balanced and unbalanced headphone output
- Output mute circuit
- Part of multi-component system with external power supply
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
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)