Qudelix T71 Portable DSP DAC & HP Amp

[amirm]

Could you please next time measure with the 8 Ohm termination instead of 12? Looking for a good portable DAC to drive Verum 2

My headphone dummy load won't go that low unfortunately.

 

[Grooved]

The 8 channels are exposed through the USB-C “auxiliary” port—see schematics in earlier post. There is a surround downmix (software) feature, but the T71 IEM is not “surround” IMO, it is a 4-way active IEM: it connects onto the USB-C auxiliary port, which enables this 4-way crossover mode in the “SPK PEQ” section. The crossover freq. are fixed (150, 1500, and 6500 Hz I believe), but each driver (1x DD + 3x BAs) has it own set of 10x PEQ filters to choose from Peak, Low-Shelf, High-Shelf, Low-Pass and High-Pass. They are applied to L&R combined or individually and the amp gain can be adjusted for each driver. Each driver can also be muted. If you add the global “USER” 10x PEQ, that’s up to 90x PEQ filters…

It looks more like they can do both, stereo with 4-way outputs, and surround with 7.1 outputs.
The website talks about the 4-way option for 2.0 audio files (first image below), and 7.1 outputs for 7.1 audio files (second image below):

2.0 audio files

7.1 audio files

 

[DanTheMan]

It looks more like they can do both, stereo with 4-way outputs, and surround with 7.1 outputs.
The website talks about the 4-way option for 2.0 audio files (first image below), and 7.1 outputs for 7.1 audio files (second image below):

2.0 audio files

7.1 audio files

As ridiculous and impractical as it may be, this makes me want to DIY a modern set of AKG
K1000--of the 7.1 variety LOL.

 

[CedarX]

It looks more like they can do both, stereo with 4-way outputs, and surround with 7.1 outputs.
The website talks about the 4-way option for 2.0 audio files (first image below), and 7.1 outputs for 7.1 audio files (second image below):

2.0 audio files

7.1 audio files

I don't think this webpage is entirely correct...

With the T71 IEM

Playing 2.0 (stereo) files, I do get the 4-way crossover feature when T71 IEM is plugged in—Low / Mid / Mid /High as in the top picture. Unmuting one driver at a time makes the crossover effect very obvious. So, I believe the top picture is correct for the T71 IEM.

Playing 7.1 channels identification test files, or the Windows "configuration" test from the Control Panel, I can reasonably hear some surround effect. It's pretty obvious between Front Left, Center, and Front Right. But, I'm not sure I could reliably identify Front Left from Rear Left. Again, for me, Side Left appears more obvious and quite distinct from Front Left or Rear Left. Also with the Windows control panel (not the online test files I played...), the T71 LCD shows which channel is actually playing: in the bottom row "BL SL FL C B FR SR BR" of the LCD, the channel being played goes from greyed to bright white, and it matches what channel I test in Windows. However, unmuting one driver at a time makes no difference for the DD (<150 Hz) and the first two BAs (150-1,500 Hz and 1,500-6.500 Hz): the Windows control panel test and 7.1 channels identification test files play normally and are audible. If I only unmute the 3rd BA (>6,500 Hz), the Window control panel test becomes barely audible, and the 7.1 channel identification test files only plays a faint buzz for each channel.
The point here is that these 7.1 tests run fine regardless of which driver is muted or not on the T71. So I believe the bottom picture is incorrect, or at least misleading, in the case of the T71 IEM: the 4 color dots on the IEM circle in the picture should not be understood as being the 4 drivers, with each one of the drivers exclusively associated with one of the 7.1 channels. I believe my earlier comment still stands, it's like: [7.1 channels] > [USR EQ on each channel] > [Downmix SW] > [Crossover + SPK EQ for each IEM driver] > [DAC-Amps] > T71 IEM.

With Something other than the T71 IEM plugged onto the auxiliary USB-C port...

Well... I have not tested this extensively as I don't have a 7.1 device readily available (Errrh, I have an old (Sony) 7.1 AVR, but it's integrated in a cabinet and I'm too lazy to declare war to all the cables and stuff in that cabinet). EDIT: and I’m too lazy to mess with a USB-C test board an a bunch of RCA cables. The T71 IEM does not appear to have an identification feature—like an unused USB-C shorted to ground or something like that: if I cycle between connecting a 3.5mm HP and connecting a random USB-C cable onto the auxiliary USB-C port, the "SPK EQ" view in the app switches accordingly from the regular 10x PEQ view to the 'crossover' view. Nothing indicates you can get the 7.1 individual channels out of the T71. It seems T71 IEM (with crossover) is the only option for now. This also matches the DAC/Amp "OUTPUT" view in the App (I was in AUTO): there is a T71 mode—for T71 IEM—but there is no 7.1 OUTPUT mode...


Pfff... that was a lot of text! Short version: T71 does have a (software) downmix feature used to play 7.1 content on regular 3.5 or 2.5/4.4mm HP/IEMs, or the T71 IEM with its 4-way crossover features (as well as QX-over and its 2-way crossover, although I have not tested it). Each one of the 7.1 channels can be EQ'd individually (10x PEQ). But, in its current state, the T71 cannot output the 8x EQ'd individual channels from 7.1 content; it has to go through the Dow mix SW which outputs two channels. So, not really usable as a 7.1/EQ compact preamp... IMO. I hope to be proved wrong !!!

 

[Merkurio]

I’ve been rocking the T71 since it launched (bought in pre-order with a small discount) and it’s been my endgame ever since, completely replacing any full-featured desktop DAC/amp combo. PEQ alone is no longer enough, and its downmixing capabilities for multichannel audio have become essential for gaming and movies in my case!

I started the official thread on Head-Fi (pretty much the only topic of that forum I actually frequent, along with the Audio Science subforum) and I was always curious to see Amir get his hands on it, but I never imagined the measurements would be this good, even knowing that audibly I wouldn’t notice any difference with a slightly lower SINAD.

My only wish now is for Qudelix to release a small desktop box similar to the Topping DX3 Pro+ (no battery, with a volume knob and with all the functionality of the T71, and if possible Bluetooth as well, for those special occasions when I want to hook up my phone).

 

[jkim]

Could you please next time measure with the 8 Ohm termination instead of 12? Looking for a good portable DAC to drive Verum 2

You don't need actual measurements. The output of this device is current-limited by the INA1620 op-amp wired in balanced mode. So, its maximum output under 8 ohm should be affected by the same current limit as with the 12, 16, 20, and 32-ohm load. Amir's measurements under all these load conditions point to the op-amp's 85 mA RMS limit.

So, under 8 ohm, the max output will be around 0.68 Vrms (or 57.8 mW). Basically, the low-impedance drive capability of T71 is not much better than that of 5K.

Sure, not a lot of output. But the primary design goal of T71 is not to achieve the best 2-channel headphone amplification, but to support unique, multi-channel capability for IEM hobbyists. For this reason, I recommend 5K over T71 if the use case is strictly 2-ch stereo. See my measurements on this page of the 5K thread. It is more than capable of serving most stereo DAC/hp amp use cases.

 

[jkim]

Later on, I realized that unbalanced output actually has a few dB lower noise floor. So here is that with 50 mv output:
View attachment 500886
View attachment 500887
So not the quietest amp but still, above average.

For this 50 mV SNR measurement of a combo device or a headphone amplifier, I wish your standard procedure included setting a device's built-in volume control, if available, to a certain low level (e.g., 200 mV @ 0 dBFS DAC or 4 Vrms HP-amp input), not just using the device's low-gain mode. Then, measure the device's SNR @ 50 mV with the test signal digitally attenuated to precise 50 mV. I am pretty sure (not 100% sure, though) that the T71 uses the ES9219's 24 dB range of analog volume control. And I know, in the case of Qudelix 5K, engaging its onboard volume control significantly lowers its low-level noise performance---see here.

 

[Yevhen]

You don't need actual measurements. The output of this device is current-limited by the INA1620 op-amp wired in balanced mode. So, its maximum output under 8 ohm should be affected by the same current limit as with the 12, 16, 20, and 32-ohm load. Amir's measurements under all these load conditions point to the op-amp's 85 mA RMS limit.

So, under 8 ohm, the max output will be around 0.68 Vrms (or 57.8 mW). Basically, the low-impedance drive capability of T71 is not much better than that of 5K.

Sure, not a lot of output. But the primary design goal of T71 is not to achieve the best 2 channel headphone amplification, but to support unique, multi-channel capability for IEM hobbyists. For this reason, I recommend 5K over T71 if the use case is strictly 2-ch stereo. See my measurements on this page of the 5K thread. It is more than capable of serving most stereo DAC/hp amp use cases.

I don't like any of those. I wanted to see SINAD closer to 110-120. So, basically, there is no reason to buy the 8-Ohm Verum 2 for portable use?

What would you say about Moondrop FreeDSP Mini HiFi Portable USB-C Miniature Decoding Amplifier CS43198 3.5mm CITA Adapter DAC AMP? I just ordered it a couple of days ago.

 

[jkim]

I don't like any of those. I wanted to see SINAD closer to 110-120. So, basically, there is no reason to buy the 8-Ohm Verum 2 for portable use?

What would you say about Moondrop FreeDSP Mini HiFi Portable USB-C Miniature Decoding Amplifier CS43198 3.5mm CITA Adapter DAC AMP? I just ordered it a couple of days ago.

Why do you need SINAD of 110 to 120 dB? On what ground? Our ear cannot perceive the difference b/w 90 and 120 dB SINAD. You may simply pursue measurably higher SINAD, though.

EDIT: Any CS43131/CS43198-based DAC/headphone amp is a step down from the Qudelix 5K or T71. First, it is affected by the Cirrus hump distortion. Second, it's low-level noise performance is far behind ES9219 which supports onboard analog volume control.

 

[Yevhen]

Why do you need SINAD of 110 to 120 dB? On what ground? Our ear cannot perceive the difference b/w 90 and 120 dB SINAD. You may simply pursue measurably higher SINAD, though.

Not sure if I need it with the headphones , but in my home setup, I can hear the difference between good (SINAD 90dB) and excellent speaker amplifiers 110dB. I got used to the sound of the Hypex / Purifi, and there is no way back.

Would Topping G5 perform better with the 8-Ohm?

 

[jkim]

I can hear the difference between good (SINAD 90dB) and excellent speaker amplifiers 110dB.

No, you cannot. The 110 dB SINAD spec should be at its max output. At your normal (even) loud listening level, your speaker amp's SINAD will be lower than that. And more importantly, consider your SPEAKER's distortion and noise, which is far, far higher than generated from any of your electronics.

Would Topping G5 perform better with the 8-Ohm?

Yes, it is a different beast.

 

[Yevhen]

consider your SPEAKER's distortion

You are right that I can't hear that low distortion, but the SINAD 90dB amp creates the IMD (especially in the kHz range of cymbals) that I believe annoys my ears. The 0.1% THD in the speaker does not create such a bad IMD as the power amp

 

[amirm]

For this 50 mV SNR measurement of a combo device or a headphone amplifier, I wish your standard procedure included setting a device's built-in volume control,

That's exactly what I do. I do this in combination with gain setting to get the best performance.

 

[jkim]

That's exactly what I do. I do this in combination with gain setting to get the best performance.

Great to know this. I assumed you just use a device's gain setting. I hope you make clear exactly what you did for each device, though.

 

[amirm]

Great to know this. I assumed you just use a device's gain setting. I hope you make clear exactly what you did for each device, though.

That's for every headphone amp.

 

[jkim]

That's for every headphone amp.

Sorry I wanted to make it clear. So, you do that even for DAC/HP amp devices? The reason why I raised this point was mainly because of your Qudelix 5K's 50 mV SNR measurement. If you had used its on-device volume control, the SNR would never have been that low at 81.7 dB which would make sense only with digital attenuation. With the 5K's volume control, the 50 mV SNR is greater than 90 dB even with CCIR-2K weighting.

 

[Rottmannash]

For just one Aux port the 5K performs just as well for <½ the price.

But yeah that is a great use case and Qudelix have created a Car power mode just for that.

Is the "Car power" mode for this device for for the 5k as well?

 

[staticV3]

Is the "Car power" mode for this device for for the 5k as well?

The 5K has it. The T71 I don't think so.

 

[Rottmannash]

The 5K has it. The T71 I don't think so.

k. thanks. I wonder if a newer version of the 5K will be released anytime soon.... I lost my 5K somewhere between the gym and home a couple weeks ago and grieved over that loss for a bit. Want to replace it but would wait for a newer version if one's coming down the pike.

 

[CedarX]

Is the "Car power" mode for this device for for the 5k as well?

The 5K has it. The T71 I don't think so.

A "Car mode" doesn't really make sense for the T71: it has no Bluetooth, so you need to connect it to some USB source... which also powers it on.