The Bush WI-1810 is a budget internet radio and Bluetooth speaker sold by Argos. At the time of writing, it was discounted to £25, but at its usual price of £49.99 it still represents the low end of the internet radio market. The radio is based on the Magic Systech platform, which is a popular platform and is found on many internet radios, but more premium brands such as Roberts and Pure use the competing Frontier Silicon SmartRadio platform. Both platforms allow set designers to incorporate a variety of features in a set including but not limited to internet radio, Bluetooth, uPnP streaming, FM, DAB+, CD player, and line in, but this set analysed here only features the first three of those features.
The current consumption of the radio is 0.25A @ 6.0V when in standby and 0.3A when on but nothing is playing. The current goes up by a negligible amount when an internet radio station is playing and the volume is turned down. When the volume is turned up to maximum, the current varies according to the audio and peaks at around 0.5A.
The level of integration in this product is surprisingly low. My original expectation was that there would be a Magic Systech-branded chip inside performing most of the key functions of the radio, much like the Frontier Silicon radios, but all of these functions are carried out by independent ICs and the CPU is an off-the-shelf one not specifically designed for radios. Despite the complexity of the design, components have been carefully selected to lower the cost whilst still delivering a reasonable level of performance where it matters - the audio quality.
Electrolytic capacitors - all off-brand through-hole 10V types, but surprisingly rated for 105 degrees C. Through-hole electrolytic capacitors are still cheaper than surface mount ones for some reason, so the extra assembly effort is often worth it.
CHMC SBE SCA108 Voltage regulator - I couldn't find anything for this part number, but the 0.33R resistor between pins 6 and 7 and the connections to the inductor, schottky diode and timing capacitor point to this being a really cheap Chinese clone of the MC34063, which itself is the cheapest widely available Western switching regulator IC. The 51k and 33k feedback resistors give an output voltage of 3.18V. This IC has a rather high maximum input voltage so this should give good headroom against overvoltage on the input.
The MC34063 is generally a good choice for this application. The only real disadvantage it has is that its switching frequency is low, which means it needs a fairly high-value inductor (typically 220uH), which is physically quite large at the regulator's typical rated current of 0.5A. Large inductors are expensive, so the designer has used a rather small inductor here.
I don't know how much current this design uses at 3.3V, or the current rating of the inductor, so I can't comment on whether it is comfortably adequate or being stressed. However, as both the inductor and chip get rather warm when the set is running, and the set uses 0.3A @ 6V when it's not producing any sound and it runs Linux, I would guess that the current it uses at 3.3V is much closer to 500mA than it is to 0mA, so if the device fails, I would check this inductor.
Nuvoton N32905U3DN main CPU - a surprisingly exotic chip which can run Linux and drive LCDs up to 1024x768. I found some limited information elsewhere on the internet which indicates that the Magic Systech software platform is Linux-based and that it is not exclusive to Nuvoton CPUs. The chip itself is not very old but the ARM926EJ-S CPU core itself is rather dated, which probably keeps costs down and contributes to the general sluggishness of the user interface.
W25Q32JV flash - this 32Mbit capacity (4Mbyte) flash chip will contain the entire program of the product as the CPU does not have any significant program memory of its own.
Super Chip SC2314 audio processor - this applies effects like volume, balance, bass, treble, etc. I'm surprised they didn't integrate these functions into the main CPU and implement them in software. Both channels appear to be in use, so there's an opportunity to mod in a stereo headphone jack to replace the mono jack it comes with. The L and R outputs from this chip go to C15 and C14, the other ends of which are connected together. I haven't tested it to see if the channels are stereo before that point.
CS8509E - Class D amplifier. Rated for operation up to 9.2V, and can deliver up to 8.5W into a 4-ohm load at 8.5V or 3W into a 4-ohm load at 5V. When powered from 6V, the maximum power would only be just over 3W at 1% THD according to a graph in the Chinese-language datasheet, which is probably why the Argos listing says it only has an output power of 3W despite the speaker being rated for 5W.
MT7601 Wi-Fi chip - commonly found in cheap Wi-Fi dongles, and probably selected for availability of Linux drivers. There is no Ethernet port on this set, which keeps the price down, but can result in reception being wiped out if the microwave is used in the kitchen (a common location to deploy a radio like this).
Bluetooth receiver - Beken BK8000 (under the sticker). This chip is commonly used on those Bluetooth-to-3.5mm modules which can be found on Aliexpress for next to nothing. Some of those Aliexpress modules look identical to the module in this radio. The module features a flash chip with a quarter of the capacity of the main processor's flash chip! All the audio decoding is done inside the BK8000, so the main processor just drives the module with some GPIO and presumably routes the audio to the speaker via the SC2314.
Speaker - 5W. This rather hefty speaker is not hi-fi quality but it's much better than that which would typically be found in an entry-level DAB/FM radio or even some entry-level boomboxes and the sound quality is quite reasonable for such a cheap set. I don't have a proper sound level meter so I can only give approximations of the frequency range, but when connected to a phone running a signal generator app via Bluetooth, the volume started to drop off below 80Hz and nothing was heard below 50Hz. At the high end, it sounded fine up to at least 9kHz.
