New .wav player from Aune looks very interesting

Thanks to jambul for alerting me to this one - ÕÔÓîΪ×÷Æ· - Aune M1 ±ãЯʽ²¥·ÅÆ÷²âÆÀ±¨¸æ [Soomal¡¤ÊýÂë¶à] (link is in Chinese but its mainly for the pics).

Notice that although its using the PCM1793 chip the D/A and analog circuits are all on a daughter board. This gives rise to the possibility of engineering a daughter board with a much better DAC chip (think TDA1387) and improved head-amp...

Street price here is around 800rmb (£80, $130) so I shall be ordering one to have a play.

Update - looks like I'm rather slow to catch on, Taobao already has somebody's alternative DAC-AMP card, which appears to be selling fairly well, here : https://item.taobao.com/item.htm?spm=...cket=13#detail

I've now placed the order for the M1, hopefully it'll arrive tomorrow and then I'll follow Dave (EEVBlog)'s advice : 'don't turn it on, take it apart'. The main question I want an answer to is how much space is available inside. Ideally for the best dynamics a transformer is called for, but they're bulky so there may well be no option but to do without, or design to use an external pair of trafos.

Reading the blurb (that's not in Chinese) it seems the battery life is quoted as 8hrs, the battery capacity is 2200mAh so this translates to a draw of 275mA from 3.6V. The PCM1793 takes 6.5mA @ 3.3V and 14mA @ 5V. The STM32 looks to run around 30mA (depending on peripherals enabled) and WM8805 is 17mA. I would guess that the large clock module in the centre might be a power-guzzler, other than that there's the Xilinx FPGA and the screen backlight. Eyeballing the daughter card from the pics available seems to show a number of screened inductors which suggests switching supplies are being used to generate higher voltage rails - two of which probably power the OPA2134 (8mA). This is certainly going to need higher rails than a single 5V simply because it can't swing at all close to the rails when heavily loaded. The DS shows the performance at 600R load (the highest likely headphone impedance) and that's only showing a possible 300mV swing from 5V. Its output current is spec'd at 35mA - which gives 20mW into 32R (the impedance the blurb mentions) - however only 1V peak is needed for this. So if the 8hrs is specified playing music into 32R phones, chances are the inefficiency of the amp has a large bearing on the battery life given that 35mA peak current is coming from the output of a boost reg. To reach 20mW into 600R needs a swing of 3.5VRMS so the rails need to be +/-7.5V minimum to the opamp, a step-up of 4X. Thus 35mA from those rails requires 140mA from the battery.

While waiting for my M1 to arrive, I've been studying the 'Choir' module (3rd party DAC-AMP) linked to above. They seem to be generating a balanced +/-9V supply from a single boost converter (SOT23-5 package) with a bridge of diodes and CLC filtering. Local decoupling for the drivers comes from 10uF/16V Elnas. With space at such a premium I can't understand why they'd use electrolytics when ceramics can pack so much more capacitance in to a smaller space. Perhaps its the street cred of Elma whereas ceramics carry no logos or come in fancy colours.

Ah - on translating some of the Chinese at Hifidiy I see its (the Choir) really designed as a companion to the B1 discrete headamp. Not for driving headphones direct. Some investigation of the B1 is now in order.... Taobao has just one seller, but trade looks to be fairly brisk - aune B1 È«·ÖÁ¢¼×Àà±ãЯHIFI¶ú»ú·Å´óÆ÷-ÌÔ±¦Íø
After translating some of the text I later found out that this is not yet a released product (hence only one seller) but the launch is intended to be CES in Jan next year. The earliest versions will be in machined aluminium but later ones they plan to be plastic cased. The orders are only pre-orders at this stage - still there's a lot of interest for something which is still vapourware

I have the device in my hands now - its reassuringly heavy and they've included a 8GB card with it. No included phones though - which tells me this is marketed at those who want something above baseline quality in their transducers. Teardown report to follow.

OK so I did do a quick listen first, before ripping it apart. A side-by-side comparison against the Ozone mobile (tea container) feeding the 50k input load of the active speakers. Music being the Missa Criolla (on Decca) by Ramirez. The M1 brings voices further forwards due to some unnatural accentuation of the upper mids. Carreras sounds much closer on the M1, a little bit sibilant. The choir sound OK (but not so well located in space) until there's a crescendo but then they become reminiscent of the choir on 'The Mission' soundtrack, shouty and rather unruly. There's quite a bit less space evident, and at higher levels there's going to be listening fatigue eventually. Generally the LF is fine (except for the reduction of depth), the problems are from the mids upwards - for example the harpsichord's attack sounds more smeared and timbrally more 'jangly'. Overall not at all bad for the price - if your preference wasn't for classical (which is spectrally more dense than more contemporary music) then you may well be quite satisfied with this as a DAC.

Some technical details concerning the DAC daughter board. Low-pass filtering of the PCM1793 is carried out by an OPA2134 which then feeds into an NE5532 with discrete current booster output stage. Power is supplied (on the reverse side of the board) from an LT1930 1.2MHz boost regulator rigged with voltage doubler diode strings to get a bipolar pair of rails around 9V. The twin rails then get LC filtered (10uH/47uF tantalums). There's a second LT1930 but I've not yet figured out what its powering. A third regulator looks to be an LDO (linear) reg, probably powering the S/PDIF output driver.

I've buzzed out all but one of the pins on the 10way connector now. Referring to the pic of the underside of the board, from the left the functions are : GND, GND, VCC, X, SHDN, S/PDIF, SCK, WS, BCK, DATA

where X = don't know yet
SHDN = shutdown signal to LT1930 regs
SCK = system clock (master clock not required by TDA1387)

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