This is a review and detailed measurements of the Qudelix T71 multichannel/stereo DSP portable DAC and balanced headphone amplifier. It was kindly drop shipped by a member and cost US $229.
While larger than the typical "dongle," the T71 is still quite light and portable despite having a built-in batter. Four LED buttons control navigation which at first seems a bit confusing but then makes sense. As far as information, the T71 blows away any other device in its class. Notice for example the one view above where it shows the voltage of the USB bus and amount of current it is using! Some temperatures are provided as well.
Much more capability is exposed through portable apps and a Chrome browser extension which I used to easily change settings.
As the name kind of indicates, the T71 is actually a multichannel DAC with mix down capabilities! I am assuming gamers will like this as probably movie watchers.
Myriad of outputs are available:
I focused my testing on balanced 4.4mm output but in some tests I also tested the 3.5mm unbalanced.
Quadelix T71 Measurements
Let's treat the unit as a balanced DAC and see how it performs starting with our dashboard:
This is nice! Distortion is near threshold of inaudibility. SINAD of 110 dB as a result is desktop-class and easily lands in upper tier of all portable DACs tested:
Since so many ask, I turned on all the user DSP filters but left them all at gain of 0 and ran the dashboard again:
I even boosted one of the above zero and it made no difference to overall performance. So don't fear about the general impact of DSP.
Max output is a whopping 8 volt (!) so I measured performance all the way up to that:
At least into this 600 ohm load that I used, best performance is around 4 volt. The higher output however, will coming handy as you mess with DSP (i.e. headroom).
Dynamic range is again desktop class:
Later on, I realized that unbalanced output actually has a few dB lower noise floor. So here is that with 50 mv output:
So not the quietest amp but still, above average.
Multitone performance again lands in the same branch of excellence:
As does jitter:
Frequency response and that of the filter is a function of the option you choose:
Wideband distortion+noise vs frequency again impresses, keeping up with best desktop DACs:
A bit of miss is signs of "ESS DAC IMD Hump" which we discovered a few years ago:
Hope the company sees this and searches for the solution that is documented on ASR.
The main event for a device like this is amount of output power. Courtesy of internal battery and great implementation, we have more than almost any portable device:
As noted above, the standard gain setting just gives you lower output levels. It has no benefit as far as lower again (hence the reason it did not do better in 50 mv test).
With so much voltage on tap, current is the limiting factor when driving headphones:
Conclusions
After testing hundreds of audio devices, not much surprises me. But then comes this T71. Across its capabilities and measurement performance, my smile and surprise factor kept getting larger and larger! Company has no business pushing the boundaries so much but I appreciate that they have. We have a tiny portable DAC & Amp which keeps up with most desktop products yet blows them away in functionality with DSP, auto-eq, multichannel support. Yes, there is a minor miss in IMD ESS DAC response but other than that, the T71 is faultless for its class and then some.
It is my pleasure to recommend the Qudelix T71.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
While larger than the typical "dongle," the T71 is still quite light and portable despite having a built-in batter. Four LED buttons control navigation which at first seems a bit confusing but then makes sense. As far as information, the T71 blows away any other device in its class. Notice for example the one view above where it shows the voltage of the USB bus and amount of current it is using! Some temperatures are provided as well.
Much more capability is exposed through portable apps and a Chrome browser extension which I used to easily change settings.
As the name kind of indicates, the T71 is actually a multichannel DAC with mix down capabilities! I am assuming gamers will like this as probably movie watchers.
Myriad of outputs are available:
I focused my testing on balanced 4.4mm output but in some tests I also tested the 3.5mm unbalanced.
Quadelix T71 Measurements
Let's treat the unit as a balanced DAC and see how it performs starting with our dashboard:
This is nice! Distortion is near threshold of inaudibility. SINAD of 110 dB as a result is desktop-class and easily lands in upper tier of all portable DACs tested:
Since so many ask, I turned on all the user DSP filters but left them all at gain of 0 and ran the dashboard again:
I even boosted one of the above zero and it made no difference to overall performance. So don't fear about the general impact of DSP.
Max output is a whopping 8 volt (!) so I measured performance all the way up to that:
At least into this 600 ohm load that I used, best performance is around 4 volt. The higher output however, will coming handy as you mess with DSP (i.e. headroom).
Dynamic range is again desktop class:
Later on, I realized that unbalanced output actually has a few dB lower noise floor. So here is that with 50 mv output:
So not the quietest amp but still, above average.
Multitone performance again lands in the same branch of excellence:
As does jitter:
Frequency response and that of the filter is a function of the option you choose:
Wideband distortion+noise vs frequency again impresses, keeping up with best desktop DACs:
A bit of miss is signs of "ESS DAC IMD Hump" which we discovered a few years ago:
Hope the company sees this and searches for the solution that is documented on ASR.
The main event for a device like this is amount of output power. Courtesy of internal battery and great implementation, we have more than almost any portable device:
As noted above, the standard gain setting just gives you lower output levels. It has no benefit as far as lower again (hence the reason it did not do better in 50 mv test).
With so much voltage on tap, current is the limiting factor when driving headphones:
Conclusions
After testing hundreds of audio devices, not much surprises me. But then comes this T71. Across its capabilities and measurement performance, my smile and surprise factor kept getting larger and larger! Company has no business pushing the boundaries so much but I appreciate that they have. We have a tiny portable DAC & Amp which keeps up with most desktop products yet blows them away in functionality with DSP, auto-eq, multichannel support. Yes, there is a minor miss in IMD ESS DAC response but other than that, the T71 is faultless for its class and then some.
It is my pleasure to recommend the Qudelix T71.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
thanks for the review, 
