Moonriver2, Jcally AP98 Measurements.

[Matias]

Well, they are clearly not the same, though JCally could argue that the extra chips are not needed to get the same measurements. Still it was a bad move from them...

 

[charleski]

It looks like the 6863 output opamps are missing, though of course we're only seeing one side of the board. When I get my AP90 I'll test how it performs into low impedances, which is where any effect would be most evident.

 

[Rusty Shackleford]

Around September, AliExpress found AP90(60$),AP98(100$) that look the same as Moon River 2(161$),
and I purchased them. In this post I will post the results of the RMAA of Moon River 2, AP98 and additionally AP90.

The biggest difference between Moon River 2 and AP98 is that when connected, gain setting is different. High gain is the default for Moon River 2, and low gain is the default for AP98.

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On 4.4 (24/192)
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I also upload the RMAA results of AP90 with the same appearance and different chipsets used. It is a great USB Dongle DAC built using AKM 4493.
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As a mobile headphone amplifier and DAC, Jcally's AP90, 98 are all recommended products. I am using 4.4 to 2XLR cable as a DAC.

Thx you.

Thank you for this. Did you find out what kind of filter (minimum phase, slow rolloff, etc.) that each uses?

 

[Jimbob54]

Well my ap90 arrived. It works!

Sounds fine to my ears. Comes well packaged. Just an FYI for anyone buying, it comes with a little carrying case (nice touch) but no cable (think there may have been options at checkout).

So if you don't have one lying around, make sure you order one with cable.

Not tried to use it with any harder to drive 'phones yet so can't comment on its absolute power.

 

[charleski]

My AP90 arrived despite all the strikes. I was hoping to do some measurements using my antique Emu 1616m (hooked up to an equally antique laptop), but this was acting up previously and now appears to be glitching too much to use without tearing my hair out. If I want to do this properly I should just get a Cosmos I suppose.

Anyway, I managed to get a few useful measurements, all taken from the single-ended 3.5mm output.

Firstly, I can confirm that this uses asynchronous data transfers (which is the optimal route), unlike other dongles like the TempoTec:

Endpoint Descriptor:
------------------------------
0x07    bLength
0x05    bDescriptorType
0x01    bEndpointAddress  (OUT endpoint 1)
0x05    bmAttributes      (Transfer: Isochronous / Synch: Asynchronous / Usage: Data)
0x0308    wMaxPacketSize    (1 x 776 bytes)
0x01    bInterval         (1 microframes)

The output impedance seems impressively low, I got a figure of 0.28ohms. 2.028Vrms across a 314.6ohm load, and 2.001Vrms across 19.6ohms, then you just do some maths. I can confirm that the 3.5mm output maxes at 2Vrms.

I also managed to take a look at the filter, which seems to be set to the 'Short Delay Sharp Roll-Off Filter' option of the 4493, i.e. minimum-phase with fast roll-off and good stop-band rejection. Below is a plot of a 100Hz square wave (44.1kHz signal recorded at 96kHz) and a 96kHz RTA plot when playing 19+20kHz tones, showing good image rejection. The linear phase filter would be optimal, but this will be fine.



The unit has various operating modes and can work as a UAC1 device for compatibility with older computers, as well as giving the option to step down the maximum voltage output. Switching these requires various tricks with pressing the buttons and the mode is indicated via three tiny leds: to see the colour properly I found it easiest to shine it on a white surface as it uses combinations of the leds that don't really cohere, 'yellow' is red + green, 'purple' is red + blue, etc, but you only see one led when looking at it as they have very narrow dispersion.

I'm listening to it now and can confirm that all the requisite veils are lifted and magical pixies are wafting gusts of musical ecstacy at me, i.e. just like any other competently-designed DAC. I use this going from an RPi running moode and plug the output into a Heresy amp. The one thing I did notice is that it's quieter than the TempoTec I was using, and I need to turn the volume up. I'm not quite sure why this is, as both have a 2V output, but maybe I should go back and check things again.

I replaced my TempoTec as it would drop the audio intermittently (about once an hour). Hopefully the asynch transfers mean that this unit won't show the same problem, but it will take time to confirm that.

 

[staticV3]

2.028Vrms across a 314.6ohm load, and 2.001Vrms across 19.6ohms

best to measure the unloaded voltage without dummy load at all, straight into the DMM or Voltmeter. Those usually have Zi in the MΩ range.

 

[Jimbob54]

The one thing I did notice is that it's quieter than the TempoTec I was using, and I need to turn the volume up. I'm not quite sure why this is, as both have a 2V output, but maybe I should go back and check things again.

When I used mine on uapp android and looked at hardware volume settings, the second set of sliders (that aren't controlled by the usual phone up /down) was less than full. Built in safety perhaps?

 

[charleski]

best to measure the unloaded voltage without dummy load at all, straight into the DMM or Voltmeter. Those usually have Zi in the MΩ range.

Well it should but … my multimeter is a rather cheap one, so I thought it best to use a couple of dummy loads.

 

[staticV3]

Well it should but … my multimeter is a rather cheap one, so I thought it best to use a couple of dummy loads.

Whatever your DMM's Zi is, adding an additional load resistor to measure unloaded voltage will make your results less accurate.
You will always get as close to truly unloaded by going straight into the DMM.

 

[alekksander]

question is: is there any reason to choose ap98 over ap90? does anyone have photos of 90's intestines?

 

[charleski]

question is: is there any reason to choose ap98 over ap90? does anyone have photos of 90's intestines?

The Cirrus Logic cs43131 chip used in the AP98 and MoonRiver 2 is capable of perfectly good performance, but it has a bug that’s exposed by full-range multitone signals. See here and here for examples. I experienced the same issue with my TempoTec. It’s easy to work around the bug by ensuring that the signal being sent to the DAC never quite reaches 0dBfs, but the AKM4493 used in the AP90 doesn’t have any bugs and is preferable for that reason.

Using two DAC chips and averaging across the outputs should lead to slightly lower noise figures, but noise from the 4493 is already at the limit of most measurements (as here), so I don’t see this as having any utility.

I can’t really see any reason to pay more for the AP98.

 

[Jimbob54]

The Cirrus Logic cs43131 chip used in the AP98 and MoonRiver 2 is capable of perfectly good performance, but it has a bug that’s exposed by full-range multitone signals. See here and here for examples. I experienced the same issue with my TempoTec. It’s easy to work around the bug by ensuring that the signal being sent to the DAC never quite reaches 0dBfs, but the AKM4493 used in the AP90 doesn’t have any bugs and is preferable for that reason.

Using two DAC chips and averaging across the outputs should lead to slightly lower noise figures, but noise from the 4493 is already at the limit of most measurements (as here), so I don’t see this as having any utility.

I can’t really see any reason to pay more for the AP98.

The 98 and the MR2 both use cs43198 https://shenzhenaudio.com/products/...dac-amp-headphone-amplifier-hifi-device-specs

But Id agree that unless power output differs significantly between the 90 and the 98 not sure why you should choose one over the other. .

 

[alekksander]

The Cirrus Logic cs43131 chip used in the AP98 and MoonRiver 2 is capable of perfectly good performance, but it has a bug that’s exposed by full-range multitone signals. See here and here for examples. I experienced the same issue with my TempoTec. It’s easy to work around the bug by ensuring that the signal being sent to the DAC never quite reaches 0dBfs, but the AKM4493 used in the AP90 doesn’t have any bugs and is preferable for that reason.

Using two DAC chips and averaging across the outputs should lead to slightly lower noise figures, but noise from the 4493 is already at the limit of most measurements (as here), so I don’t see this as having any utility.

I can’t really see any reason to pay more for the AP98.

excellent reply, thank You.

still looking for AP90 pcb, but perhaps i'll be the one posting it after all (if it's possible to disassemble -- wondering about oper. amps., or actually the lack of it). anyhow i'm getting AP90 over 98 and Space.

 

[MCH]

Well, then there is the moral side of it, right. I get the impression from previous posts that this might be a counterfeit and Moondrop (that provides us with cheap items and oder gadgets we adore) is not very happy about it....
Not claiming that this is true, maybe it deserves some research, but I personally would not order for the moment.

 

[Jimbob54]

Well, then there is the moral side of it, right. I get the impression from previous posts that this might be a counterfeit and Moondrop (that provides us with cheap items and oder gadgets we adore) is not very happy about it....
Not claiming that this is true, maybe it deserves some research, but I personally would not order for the moment.

Well - its not a counterfeit- its not purporting to be the Moondrop, use their branding etc. It shamelessly copies the physical design and they seem to be trying to poach MD trade by claiming to be the the OEM manufacturer of the MD devices - their line being their devices are something of a bargain as they are the "same" with a different badge.

 

[charleski]

The 98 and the MR2 both use cs43198 https://shenzhenaudio.com/products/...dac-amp-headphone-amplifier-hifi-device-specs

But Id agree that unless power output differs significantly between the 90 and the 98 not sure why you should choose one over the other. .

Odd, I was sure I read somewhere that it was the 43131, but you're right. Both chips use the same DAC core, but the 43131 has an integrated headphone amp.

 

[charleski]

An update on the volume issue on Linux systems (running moode which is basically a wrapper for mpd and alsa).

I have volume set to “Fixed (0dB)” in moode, but found that amixer -c2 controls listed two devices with volume capability (one of which is probably the RPi’s built in headphone jack they're both linked to the AP90, which was selected by -c2).
amixer -c2 get PCM showed a stereo device set to maximum volume
amixer -c2 get PCM,1 showed parameters for a device it regards as mono with volume set to -20dB.
So I tried amixer -c2 set PCM,1 100% and … boom (literally, make sure to turn down the volume on your amp before doing this) I’m now getting full volume from the DAC.
One thing I’ve also found is that you must restart mpd (in moode you can do this by going to configuration->mpd and simply pressing SAVE without changing anything) after any change to the system settings (or indeed simply unplugging and plugging back in). Otherwise the sound is severely distorted. But after mpd restarts it all works fine.

 

[alekksander]

An update on the volume issue on Linux systems (running moode which is basically a wrapper for mpd and alsa).

I have volume set to “Fixed (0dB)” in moode, but found that amixer -c2 controls listed two devices with volume capability (one of which is probably the RPi’s built in headphone jack).
amixer -c2 get PCM showed a stereo device set to maximum volume
amixer -c2 get PCM,1 showed parameters for a device it regards as mono with volume set to -20dB.
So I tried amixer -c2 set PCM,1 100% and … boom (literally, make sure to turn down the volume on your amp before doing this) I’m now getting full volume from the DAC.
One thing I’ve also found is that you must restart mpd (in moode you can do this by going to configuration->mpd and simply pressing SAVE without changing anything) after any change to the system settings (or indeed simply unplugging and plugging back in). Otherwise the sound is severely distorted. But after mpd restarts it all works fine.

perhaps the gain setting reported as another volume? how does this correlate to "hardware" controlled gain? by the way i've had weird double volume control experience in ALSA before with XU208/ES9038Q2M DAC. i think alsa knows too much

 

[Jimbob54]

An update on the volume issue on Linux systems (running moode which is basically a wrapper for mpd and alsa).

I have volume set to “Fixed (0dB)” in moode, but found that amixer -c2 controls listed two devices with volume capability (one of which is probably the RPi’s built in headphone jack).
amixer -c2 get PCM showed a stereo device set to maximum volume
amixer -c2 get PCM,1 showed parameters for a device it regards as mono with volume set to -20dB.
So I tried amixer -c2 set PCM,1 100% and … boom (literally, make sure to turn down the volume on your amp before doing this) I’m now getting full volume from the DAC.
One thing I’ve also found is that you must restart mpd (in moode you can do this by going to configuration->mpd and simply pressing SAVE without changing anything) after any change to the system settings (or indeed simply unplugging and plugging back in). Otherwise the sound is severely distorted. But after mpd restarts it all works fine.

Looks like a more technical view of my experience on Android with UAPP https://www.audiosciencereview.com/...2-jcally-ap98-measurements.39468/post-1410930

 

[charleski]

perhaps the gain setting reported as another volume? how does this correlate to "hardware" controlled gain? by the way i've had weird double volume control experience in ALSA before with XU208/ES9038Q2M DAC. i think alsa knows too much

It's odd, alsa seems to treat the card as if it has two volume controls. If I set the volume type to "Hardware" or "Null" then I get no sound at all. On these settings the output of amixer -c2 contents is

numid=3,iface=MIXER,name='PCM Playback Volume'
  ; type=INTEGER,access=rw---R--,values=2,min=0,max=127,step=0
  : values=0,0
  | dBminmax-min=-63.50dB,max=0.00dB
numid=4,iface=MIXER,name='PCM Playback Volume',index=1
  ; type=INTEGER,access=rw---R--,values=1,min=0,max=127,step=0
  : values=127
  | dBminmax-min=-63.50dB,max=0.00dB

I.e. the first mixer is set to 0 and there's no sound.

Given that @Jimbob54 is finding a similar result on Android, it seems that this unit is reporting its volume control in a way that's slightly confusing to linux-based systems. Luckily it's easy to fix as long as you have an interface that lets you dig a bit deeper.