Our team member Andy has written a step-by-step guide how to use the HiFiBerry DAC together with Volumio for music playback. Have a look at it!
Category Archives: Information
A HiFiBerry DAC installation using a linear power supply
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Here comes another nice HiFiBerry DAC installation. Jens from Germany doesn’t like switching mode power supplies for audio. Therefore he created a HiFiBerry setup with a huge linear power supply. Note that the power supply needs to provide at least 5V/1A for a stable operation of the Raspberry Pi. Depending on the input voltage this means heat. He uses a large heat sink and a small ventilator to get rid of the heat.
A spanish HiFiBerry Digi user has written a guide how to configure XBMC. If you are spanish-speaking, have a look at it.
A standalone streaming media device based on Raspberry Pi and HiFiBerry DAC
This is the most advanced HiFiBerry DAC setup we have seen so far. A German user integrated not only the Raspberry Pi and the DAC in a nice enclosure, but also a switching power supply. Power is connected using the onboard header on the HiFiBerry DAC and a USB WiFi Dongle is used for wireless connectivity.
Cheat sheet: sample rates and clock frequencies
I2S audio connections usually use 3 different clocks: a frame clock, a bit clock and a master clock that must be synchronized. This is just a small sheet showing different sample rates for the standard sample rates. One thing that is important for anybody designing I2S audio interconnects: The frequencies can be relatively high. Make sure, you keep the traces as short and use countermeasures against ringing. Otherwise your circuit might interfere other devices.
| Sample rate | 32xfs | 64xfs | 128xfs | 256xfs | 512xfs |
|---|---|---|---|---|---|
| 44.1kHz | 1.4112MHz | 2.8224MHz | 5.6448MHz | 11.2896MHz | 22.5792MHz |
| 48kHz | 1.536MHz | 3.072MHz | 6.144MHz | 12.288MHz | 24.576MHz |
As we start looking into Class-D audio, we want to see what’s going on above the audio band. Now, a new instrument arrived – a spectrum analyzer with integrated tracking generator. It is the Rigol DSA815. For its price, the build quality is very good. Unfortunately we have to get some test cables with N-plugs first. Therefore we can’t say much about it now.
Stacking headers
Some HiFiBerry users asked how to connect other devices to the Raspberry Pi with HiFiBerry DAC installed. An easy solution are stacking headers. It took us some time to find a supplier for these headers, but finally we got a few. A HiFiBerry DAC with the stacking header instead of the normal 26-pin connector looks like this:
The headers are now available in our HiFiBerry shop.
Comparisson IIR and FIR filters
There are lots of discussion in the DIY loudspeaker community, if digital loudspeaker crossover filters should be designed using IIR (infinite impulse response) or FIR (finite impulse response) filters. As IIR-capable DSPs are usually cheaper, many people use them.
This short article should give some information about advantages and disadvantages of both filter types.
Comparison of IIR and FIR filters
| IIR | FIR | |
|---|---|---|
| Feedback | yes | no |
| Latency | low | high |
| Processing complexity | low | high |
| Comparable to analog circuits | yes | no |
| Linear phase filtering | no | yes |
One argument often used pro FIR and contra IIR filters is the phase response. It is possible, to design FIR filters, that change the frequency response, but not the phase response – so-called linear phase filters. However, have a look at real circuits and even a loudspeaker. No real circuit with capacitors or inductors used for filtering is a linear-phase system. Also a loudspeaker chassis changes its phase response depending on the frequency. Even in high-end speakers, passive LC-crossovers introduce phase shifts. It seems, that a changing phase response is not the worst thing in the world.
There are two major disadvantages of FIR filters: the need a lot of processing power and they introduce a longer delay than IIR filters. Depending on the hardware used, the first issue might not be a disadvantage. But the delay can be a problem in many use cases.
Are FIR filters bad? No, but you should understand the differences of IIR and FIR filters and then decide what kind of filtering you need. For loudspeaker crossovers, IIR filters often work well – as the old school passive filters did before.