Fosi Audio DS2 Portable DAC & Amp Review

[AJAPE]

First of all, just a quick heads-up to those considering getting the DS2 specifically through Aliexpress: I bought one that was advertised as the DS2 DS512 model, which comes with the ESS9018K2M chip, presumably the older version. What arrived was clearly the newer dual CS43131 configuration. It says so in the included user manual, and I've manually confirmed that pressing both volume buttons at the same time does nothing (no separate low/high gain modes). Now, for me this is not really a drawback; however, those specifically wanting one version over another should take the information listed by third-party vendors with a big grain of salt! As for the power output, it is listed in the included manual as SE 128mW (32Ω) / BAL 170mW (32Ω). (The ESS version I thought I bought was advertised as having a balanced output of 510mW, but who knows if that was ever really the case?)

Finally, I have a question that I hope someone here can answer. If the balanced output merely offers 170mW compared to 128mW SE, how much additional headroom are you realistically getting in terms of volume? I’m another 490 Pro owner, and my EQ settings have a preamp gain of -6.8 dB. Will going balanced make much of a difference?

About hd490pro I've seen one post somewhere forgot where that guy tested the Fosi ds2 the CS version with sundara (measures 300ohm~) balanced vs his macbook pro (silicon) and got comfortable volume of 89% on macbook and 55% volume on ds2 balanced. Since hd490 pro is half the impedence 130ohm should be good enough I think.

(EDIT: I found the review)

Fosi Audio DS2 (2024 Cirrus Version) - Reviews

www.head-fi.org

 

[Jim Creek]

I just bought a Fosi Audio DS2 (Cirrus version) on Amazon, $60. It’s curious that the older DS1 is more expensive, $72 on sale. The DS2 gets the best reviews.

 

[fws]

About hd490pro I've seen one post somewhere forgot where that guy tested the Fosi ds2 the CS version with sundara (measures 300ohm~) balanced vs his macbook pro (silicon) and got comfortable volume of 89% on macbook and 55% volume on ds2 balanced. Since hd490 pro is half the impedence 130ohm should be good enough I think.

Sundara has 32Ohm specified, and 38Ohm measured, not 300Ohm. This further means that if his Macbook Pro was 2021+, then the Mac's output into such low impedance would be limited to 1.25Vrms (about 50mW at 32Ohm). Also you can't just compare 2 headphones by impedance without accounting their sensitivity.

 

[Jim Creek]

So, does the DS2 exhibit the Cirrus Logic distortion ‘hump’?

 

[torgeirs]

If the balanced output merely offers 170mW compared to 128mW SE, how much additional headroom are you realistically getting in terms of volume?

The output can be current limited or voltage limited dependent on headphone impedance.
Power = current x voltage
current is typically 100 mA max
Voltage 5 volt se max, 10 volt bal max.
So bal can be 6 dB more than se or just about 2 dB if the output is current limited.

 

[torgeirs]

So, does the DS2 exhibit the Cirrus Logic distortion ‘hump’?

Yes, but way down in the noise

 

[Jim Creek]

Yes, but way down in the noise

I’m curious why that distortion hump didn’t show up in Amirs review?

 

[CedarX]

I’m curious why that distortion hump didn’t show up in Amirs review?

Amir standard set of measurements is a proxy for “good engineering”. It doesn’t mean it covers everything… As @jkim showed in their measurements, the CS hump is relatively easy to detect if you know what to look for, but it’s true audibility is debatable.
It doesn’t invalidate Amir’s assessment at all. The disappointing part IMO are the OEMs: they should know better and pay attention to these “details”.
Not sure about Fosi…

 

[jkim]

So, does the DS2 exhibit the Cirrus Logic distortion ‘hump’?

According to the measurements made by RAA, the DS2 has no "Cirrus hump" by the definition given by my review. However, I strongly suspect that it must exhibit the distortion at the initial rising part of the test signal shown in Part II of my review, just like the JCally JM20 or JM20 Max.

 

[Broccoli]

Thanks for weighing in everyone! @AJAPE @fws @torgeirs

So, please correct me if I'm wrong about any of the points below:

In the review quoted above the DS2 and the Sundara needed 70.8% volume for SE to reach 90+ dbSPL, and 55.7% volume for balanced. This amounts to roughly a difference of 2dB, which is a fair bit of extra headroom; and the Sundara therefore benefits from balanced. A 2dB difference suggests the Sundara (32Ω–92dB/mW) is current limited, correct?

In contrast, the HD 490 Pro (130Ω–96dB/mW) would be voltage limited? However, the stated specs for the DS2 (balanced: 170 mW/32Ω) implies that the dongle is not delivering the full 2× voltage swing in balanced mode, and the 490 Pro would therefore gain less from going balanced than the Sundara?

 

[torgeirs]

In contrast, the HD 490 Pro (130Ω–96dB/mW) would be voltage limited? However, the stated specs for the DS2 (balanced: 170 mW/32Ω) implies that the dongle is not delivering the full 2× voltage swing in balanced mode

Yes that will be voltage limited and current limited.
So between 2 and 6 dB the voltage in balanced. In theory it will reach 170mW with 130ohm.
Volt = Ampere x Impedance, ish
10 volt = Ampere x 130 ohm
So current is under about 70 mA.
Then maybe it is a thermal problem that all amps reach at some point.

To complicate things the crest factor of the music may give room for more voltage within the thermal limits

 

[Jim Creek]

The DS2 works with my iPad and Macbook M1. When I use a USB-C to Lightning adapter on my iPhone XR I get nothing. The DS2 doesn’t power on, no LED light, nothing.

Any ideas why the DS 2 does not work with my iPhone XR with an USB-C to Lightning adapter?

 

[Somafunk]

The DS2 works with my iPad and Macbook M1. When I use a USB-C to Lightning adapter on my iPhone XR I get nothing. The DS2 doesn’t power on, no LED light, nothing.

Any ideas why the DS 2 does not work with my iPhone XR with an USB-C to Lightning adapter?

View attachment 461221

You will need to get a suitable lightning to usb c cable with pass through audio functionality, such as the cable below which I own and occasionally use with my iPhone XS/Aful Snowy Night dac/amp dongle

SHANLING L3 Neotech Pure Silver Audio Cable Type-C / Lightning to Type-C Interface for UA3 UA5 DAC iOS Android

https://www.aliexpress.com/item/1005004708692659.html?spm=a2g0o.order_list.order_list_main.16.461518025RDkI7

 

[torgeirs]

For the noise and/or hump

Fosi Audio DS2 Portable DAC & Amp Review

Hello =) Can I buy a cable from 4.4mm to 2 XLR (R + L) and use FOSI DS2 with active XLR studio monitors for example? You absolutely can. Just be careful about software volume control.

www.audiosciencereview.com

 

[torgeirs]

Way, way below the cans

 

[torgeirs]

Oops estimated poorly max rms voltage for differential.
42mW at 300 ohm acording to amir
That is little over 3,5volts rms

 

[torgeirs]

172mW at 33 ohm is 2,4 volts rms and 72mA rms

So 3,5 volts max and 72mA max
That puts the 130 ohm cans closer to 6dB gain at full volume with ballanced versus SE

 

[torgeirs]

And about 120 mW balanced vs 30mW unbalanced.
Then 96dB/mW
3dBs gain per doubling of watts.
Amir tests his speakers at 86, 91 and 96 dBs. Most home speakers start to struggle at 96 dBs

 

[Broccoli]

172mW at 33 ohm is 2,4 volts rms and 72mA rms

So 3,5 volts max and 72mA max
That puts the 130 ohm cans closer to 6dB gain at full volume with ballanced versus SE

Thanks for elaborating! If 130 ohm headphones get anywhere close to 6dB gain with balanced, then it is absolutely worth it to go balanced!

I just read through this entire thread, and there was someone who actually measured the performance for both balanced and single ended. I'm not qualified to make sense of the measurements themselves, but I'll link them since the question of output power seems to come up regularly!

Balanced power measurements: https://www.audiosciencereview.com/...ble-dac-amp-review.57063/page-20#post-2102639

Single ended power measurements: https://www.audiosciencereview.com/...ble-dac-amp-review.57063/page-30#post-2133032

 

[torgeirs]

Yes those measurements and comments are from a real professional. RME is pro gear.
I think the consensus is that distortion from amp can’t be heard. Just the artifacts that annoys a few.
If it is loud enough with SE then balanced is overkill. If it is not loud enough, go balanced.
My 600ohm old cans with this amp are way loud enough with SE