I bought a second hand M-DAC a while ago to have a well-known commercial reference in terms of measurements and sound. After teardown it is time for measurements. This first part consists of basic performance measurements.
Small sealed subwoofer stands for desktop monitor speakers
- Tang Band W6-1139SIF 6.5″ woofer
- Sealed cabinet with around 10 litre volume
- Form factor to fit behind computer monitors; white paint and black fabric finish to fit desktop environment
- Linkwitz Transform and digital room correction on miniDSP
- Woofer size and cabinet size limit performance but gives solid boost for small speakers
I bought a second hand M-DAC to have a well-known commercial reference in terms of measurements and sound. Obviously I needed to open it and see what’s inside. This is not a detailed reverse-engineering report but a glance inside with plenty of photos. Measurements are coming later.
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.
- 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
- 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:
- 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.