Khadas Tone2 Pro

I just received a Khadas Tone2 Pro DAC/Amp in the mail today. It’s a diminutive USB, I2S, S/PDIF DAC based on the ES9038Q2M DAC chip and XMOS XU216 processor. It sports both single-ended and balanced outputs for both headphones (3.5mm TRS and 4.4mm Pentaconn) and fixed line out via novel hybrid balanced RCA jacks. It’s the smallest and least expensive full MQA Decoder DAC that I’m aware of.

I’ll reserve judgement on sound quality until I’ve had more time with it. I also want to try it in a couple of different systems with the recommended balanced RCA to XLR cables. However, so far, I’m certainly not hearing anything objectionable. Perhaps a little dark sounding fresh out of the box, that could be my ears today too (feeling a little stuffy).

This is not (yet) a Roon Tested DAC, but compatibility with Roon is great. The knob on the DAC can be used for play/pause/skip. I’ve verified that this works with Roon on macOS, but I’ve not attempted to set that up on my VitOS endpoint (probably requires Roon Extension Manager). I’ll be surprised if this does not work “out of the box” on RoPieee.

The rotary volume knob / controller only attenuates output from the headphones jacks; the RCA outputs are always fixed output. This seems like a reasonable decision, but it’s something to be aware of if you want to use it with powered monitors.

This is the first time that I’ve seen a USB-C style I2S input on a DAC. I’m not a huge fan of external I2S, but in the unlikely event that I can find a transport with compatible output, I’ll give it a try.

Fit and finish of the Tone2 Pro is very good. The volume knob is lightweight but has a nice feel. Pulling it forward twice to cycle through modes is a bit funky, as is the kaleidoscope of colors that indicate various operational settings and filters, but it all works as advertised.

The Tone2 Pro runs a bit warm. I measure a current draw of about 420 mA, so in spite of its small size, it will not be the best choice for a long flight (or even a long walk) as it will run down the battery in your phone rather quickly. Apart from that, it works fine as an OTG DAC with the supplied USB-C cable and USB Audio Player PRO, including MQA Decoding and Rendering.

The headphone amp has two gain settings, but with my 25Ω E-MU Wood Series headphones, I’m only able to raise the level up to 50% in low-gain mode before it’s thunderously loud. In spite of that, the amp is dead silent at low levels, so even high-efficiency IEMs should be fine.

Driving my 300Ω Sennheiser HD650 via the 4.4mm balanced output, I do have to rotate the volume knob past 50% in low-gain to achieve satisfying levels, but there’s still plenty of range remaining. I would not want to listen at 100% for more than a few seconds! In high-gain, it feels like there’s endless headroom. The manual does say that the maximum headphone impedance supported from the 3.5mm is 150Ω (300Ω via the 4.4mm Pentaconn). I’ve not tried my HD650s with a single-ended cable, but I’d be surprised if high-gain failed to provide adequate levels.

I’ll report back later once I’ve had a chance to try the DAC with the balanced RCA cables, but if you’re looking for a Roon compatible DAC/Amp with full MQA decoding, the Khadas Tone2 Pro seems like a solid choice based on my hour or two of playing with it.

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Balanced from usb power that will be a draw on a pi for sure?

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Yes. But I do have an iFi Audio micro iUSB3.0 between the VitOS RPi4 and the Tone2 Pro. This alleviates the need for the RPi to provide power to the DAC.

I learned today that the “I2S” input on the Tone2 Pro may be used as an auxiliary power input. I’ll share measurements this evening to see how much that reduces current draw from the RPi4. Probably quite a bit.

In the “transportable” use case, I suppose that a portable charger could be used to power the Tone2 Pro so that it does not run down an attached smartphone.

Update: I’m now using an iFi Audio iPower X to power the Tone2 Pro via the “I2S” input. In this configuration, I measured 0.00 A of current draw from the host computer, so if you’re taking the Tone2 Pro on a long trip, plan on powering it separately so that it does not run your device’s battery down.

It’s a very low-noise device now matter how it’s powered, but I have to imagine that there are sonic benefits to feeding it independent, clean power. Wish I had a way to measure and confirm, but Amir over at ASR will get to that soon enough. Preliminary measurements from the manufacturer are impressive:

If verified, the number of $200 MQA Full Decoder DACs that match this performance is zero and likely to stay that way for sometime. :slight_smile:

Think about to buy this and usen in my Roon chain as an dac/amp. Got a laptop and using v40 as endpoint now. Is the Khadas good? Thought also about Ifi Zen Dac an Zen Can combo or iDSD micro BL. But this little piece seems good! Only IEMs/Oppo Pm3

My V40 quad dac sadly has limitations cause of Android

Yes. I have the LG V35. It’s fine on its own, but does not play well with Roon thanks to the Android O/S mixer. Nice as the quad DAC is, the Khadas Tone2 Pro is quite an upgrade.

In a Roon setup, I’d pair the Tone2 Pro with an RPi4 running VitOS or RoPieee. Consider one of the two Allo power supplies to separately power the DAC (basic, fancy, or very fancy).

Just be aware that you won’t be able to control the volume in Roon (unless you resort to DSP volume). Also, as I previously mentioned, the RCA output levels are fixed, so if you use the DAC with an external amplifier, it will need its own volume control.

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After letting this thing run-in overnight, it seems to have opened up a bit (or my sinus congestion is somewhat alleviated). Either way, I’m enjoying the heck out of it. :slight_smile:

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Im a Roon noob! Im learning and researching all the time now since i want to build my self a setup for iem/ headphones. Why do u use RPi4 with Vitos or RoPieee Khadas? What does that do?

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For best sound quality, Roon Labs recommends using physically distinct, networked devices for Core, Outputs, and Controls. The RPi4 is a network bridge, making a USB DAC network-accessible by Core without directly connecting it to Core or a Control. More info about this here: https://help.roonlabs.com/portal/en/kb/articles/sound-quality

It’s not super critical, but there more benefits to this than potentially nicer sound quality. The real power of Roon comes from managing multiple Outputs, Controls, and Displays. It’ addicting. :slight_smile:

Thanks for sharing your experience with the Tone2!

I’m not sure whether this is the right place to ask this, but I’ll give it a shot anyway.

I own a pair of Sennheiser HD 560s cans and recently purchased a second-hand Atom amp. To finish the stack, I have ordered the Tone Board 1 DAC straight from the Khadas website. However, I just realized that the Tone Board 2 might be a better solution since I primarily use Tidal.and full MQA would be nice. I’m worried about the capabilities of the integrated amp, which would be fine for my headphones, but it wouldn’t be as future proofing as having the Atom + KTB1 stack instead. (I will definitely upgrade in the next 2 years so that’s what I am worried about.)
The KTB2 on its own would be also cheaper a bit.

Any thoughts?

Thanks!

Hi @Pavel_Nemecz. I’ll share some measurements of the Tone1 vs Tone2 Pro this weekend that may help you decide. The reason I’m interested is because the Tone1 has some aberrations in response at the top end when decoding PCM content. I’m curious to know if the Tone2 Pro is different. For example, here’s a plot of the amplitude response of the Tone1 with a 48 kHz PCM sweep vs. a DSD64 sweep:

Now, the vertical scale is very tight, so I can’t imagine that any of this is audible, but my other DACs don’t exhibit this behavior…or certainly not to this degree.

As I type this, I’m listening to psytrance (Infected Mushroom) via Sennheiser HD 650 with a balanced cable. Some folks claim the internal amp in the Tone2 Pro lacks dynamic punch, but I’m not experiencing any of that here. As mentioned earlier, I’m powering it with an iFi Audio iPower X 5V via the I2S input, so perhaps this enhances performance a bit over just relying on USB bus power.

With the HD 560S’ 120Ω impedance, you’ll be riding the Tone2 Pro at near the top of the volume range for satisfying levels from the single-ended output–even in high-gain mode. Unlike the HD 600 family of headphones, there does not seem to be a way to mod the 560S to use a balanced connection (without major surgery), as this requires independent negative leads for both channels.

Honestly, if I was in your situation, I’d still order the Tone2 Pro and plan on pairing it with an external amp, especially if MQA decoding matters to you. It does a great job in this regard. The play/pause/skip features are nice too. It’s just a wonderful all around product. The difference in quality and function is greater than the $120 difference in price, IMHO.

I have the THX AAA 789 amp and will put that in front of the Tone2 Pro once my balanced RCA to XLR cables arrive. I do expect this amp to elevate the performance, but I’m not sure to what degree.

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Thanks for your reply. What I’m trying to achieve here is the “best bang for buck” solution as I’m a UNI student and any sort of savings are more than welcome under nowaday’s circumstances.

According to the Hifiguides thread, these cans can be easily run balanced by simply using, for example, this balanced cable along with a 2.5mm to 4.4mm adapter (can’t link more than 2 links)

What is your opinion on this, if I may ask?

If that is true, as per the mentioned discussion, I’ll have to cancel the KTB1 order and pull the trigger on the KT2pro instead.

Regarding the MQA, I have no idea if it brings any sort of a better listening experience or not, but since I’m paying for the Tidal Master subscription, it would be a nice touch indeed.

Thank you

If you can run your 560S balanced, this is a no-brainer. Even if you can’t, I’d drop the Tone1 and go with the Tone2 Pro. You’ll be glad you did.

Thank you very much, I’ll cancel the order then and order the Tone2pro instead. Or should I wait for your measurements first? :smile:

Don’t wait. Worst case, the measurements are identical, but the Tone2 Pro is still so much nicer. You won’t regret it.

Pulled the trigger today, it should arrive in 2 weeks, hopefully earlier. Can’t wait!

I was also wondering whether this brick would be able to run the KT2pro by any chance?

Thanks :slight_smile:

Says output is 5V, 2A, which is plenty of current for the Tone2 Pro. Highest I measured was 420 mA. Congrats.

BTW, I’m working on creating updated plots today. Here’s my fresh measurements of the Tone1 at different sampling frequencies.

Tone2 is next…

Before I run sweeps on the Tone2 Pro at various frequencies, I thought I’d try the seven different filters at 48 kHz. the good news is that the response looks much better than the Tone1. Bad news is that the filter selection does not seem to be working. I have a number of other DACs that support different filters, and cycling through them significantly changes the response, especially at lower sampling frequencies. Here, the results are EXACTLY the same, regardless of filter selection. I suspect this is a bug.

Okay. Wait is over. Here are plots for the Tone 2 Pro:

Since most of our music is still redbook format (44.1 kHz), here’s a comparison of the Tone1 vs Tone2 Pro at that sampling rate:

As you can see, this looks like a significant improvement. Not sure how audible this is.

Oh, I should also mention that the single-ended RCA output on the Tone1 is 1.14 dB hotter than the Tone2 Pro. So, if you are doing your own listening tests, you’ll need to account for this difference in volume. Add -1.14 dB of attenuation in Roon’s Headroom Management DSP to the Tone1 zone.

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Hey! How high DSD can the Khadas 2 do? Seems like there is ALOT of features for 199! What is you opinion about it?

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