Slightly less than a year ago I reviewed the AudioPhonics RaspTouch, a Raspberry Pi based
streamer with touch screen that uses an audio board based on the ES9028 DAC chip.
Now that the ES9038 became available, it replaced the 9028 in the AudioPhonics program.
The I-Sabre ES9038Q2M on review here is AudioPhonics' top model Raspberry Pi DAC, costing 129 Euros.
As said it is designed to be used with Raspberry Pi computers, less the first model and the Zero.
But if you want to use it stand-alone, that's possible too: just connect an SPDIF or
I2S signal to either input and add a 5 volt DC power supply.
You can also add a small screen, a volume control and an electronic power switching
unit that lets you safely power down the Raspberry Pi as with ATX computers.
The first thing to notice is that the RCA audio outputs and the Micro USB power input
are on the short side of the board so that they end up above the USB and network sockets
on the Raspberry Pi.
That might seem trivial but if you want to mount it all in a nice housing, this is far
more convenient that having the audio outputs and the power input above the power input
of the Raspberry Pi on the long side.
Indeed, you can power the DAC and the Pi through the DAC board.
On the board we see the local voltage stabilisation and a DC/DC converter that up-converts the
voltage to 9 volts DC for the analogue audio.
An Altera programmable Logic device and a Nuvoton micro-controller do the housekeeping.
The ESS ES9038Q2M takes the central position with close by the clock crystal.
The high quality op-amps, NJM 2114's, provide the current to voltage conversion to drive
the analogue outputs.
The best way to describe the sampling rate specs is: more than the Raspberry Pi can handle.
The board can playback anything PCM up to 32 bit 768 kHz but the Pi is 'limited'
to 384 kHz.
The same goes for DSD: the board can handle DSD512 but on the Pi the max is DSD128.
I wouldn't loose any sleep over it; there is hardly interesting music available at those
extreme sampling rates.
I hardly ever mention measurements since they can only proof if the design is poor but never
if the sound is excellent.
In this case measurements of both DAC's are virtually identical, showing the same
fingerprints for distortion, impulse response and noise.
Only the last was about 2 dB's lower, which is an achievement in the technical sense but
I wonder if that is audible.
It certainly isn't in the direct sense.
It makes you wonder if there is an audible difference, but I'll get back to that later.
The similarity also means that they prolonged the use of linear phase filters.
These offer a sharper edge detail as where I prefer the milder character of minimum phase filters.
I know, that's personal.
The DAC will play as is, but if you want to dress it up, AudioPhonics offers not only
all kinds of housings but also the modules I mentioned earlier.
These four pins can be connected to a rotary encoder with push function.
Rotating will vary the output volume, pressing will switch between the I2S and SPDIF input.
Nowadays digital volume control - when done properly - can be as good or even better than
analogue volume control.
See my video "Does Digital Volume Control Really Suck?".
The SPDIF input is on the pcb as are solder terminals for I2S if you want to use the board stand-alone.
Normally the I2S connection to the Pi is made over the GPIO connector.
A small OLED screen can be connected to these pins and will show the input chosen, the volume
setting from 0 to 100 and the sampling rate.
Replacing the 9028 board in my RaspTouch for the 9038 board was a breeze since they are pin compatible.
Only the SPDIF input needed to be desoldered from the 9028 and soldered to pin connectors
for the 9038 board.
Like the 9028, the 9038 on test here functioned well with Volumio, PiCorePlayer, DietPi - and
thus all programs it can install - and Ropieee.
These players were all functionally tested but for the listening test I used Ropieee
on two Raspberry Pi's, one with the old 9028 and one with the 9038 DAC.
Both were initially powered by standard 5V switching mode power supplies that were later
on replaced by an sBooster linear power supply.
The reason for this was that there was hardly any difference between the boards using the
cheap power supplies.
Using the linear power supplies not only improved the sound quality on both boards, it als made
the difference easier to identify.
Just a short remark for those that have mailed me in the past, saying that there is no difference
between a Raspberry Pi DAC using either a switching mode power supply or a linear power
supply: I believe you; I don't question your judgement.
I do question your equipment and the way it is set up though.
For even on my sub-one thousand euro setup 1 the difference is clearly audible.
Less audible on setup 3 is the difference between the two DAC's.
On the new DAC the lows are somewhat more defined, there is less colouration on voices
and the midrange in general opened up somewhat.
On my 4000 euro setup 2 these differences were more apparent.
Not that I would prefer it over the Chord Mojo in that setup, of course.
But even in my 20k setup 1 the 9038 sounded pleasant.
It obviously lacked a lot of qualities the SOtM/Mytek combination has, but it never sounded
harsh or glassy.
AudioPhonics apparently wants to keep in the forefront of the high quality DAC boards for
Raspberry Pi.
And they manage quite good: I called the 9028 DAC the best Pi-DAC I know, that position
is more PR less taken over by the 9038 that, by the way, comes at the same price: 129 euros
including VAT.
A disclaimer: I haven't reviewed all Raspberry Pi DAC's there are, so if a manufacturer
is convinced they make an even better product: just let me know and we can setup a review.
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I am Hans Beekhuyzen, thank you for watching and see you in the next show or on theHBproject.com.
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