New Topping L70 is just insane.

[Veri]

If we plot Amir's load sweep measurements of headphone Amps as Max voltage before clipping vs impedance, we see some seriously sketchy behavior indicative of either some strange limiting system in the amp, or an erroneous measurement setup.
Since this happens with every single headphone amp Amir measures this way, we can conclude that it's his setup.
See here. Red shows how we expect a headphone amp to behave (it's what Wolf measured), blue is what Amir got.

Doesn't Amir use Neurochrome's dummy load system? I always thought Amir's headphone amp measurements were actually more indicative of real-world, rather than synthetic measured performance. Not sure what kind of load @WolfX-700 uses..

 

[staticV3]

@WolfX-700 what dummy load are you using for your headphone Amp reviews?

@amirm when using your Neurochrome HP-Load to test headphone Amps, are you using it as purely resistive load, or do you enable some parallel load capacitance?

 

[Biovexo]

On the L70 as a pre (and only on the L70), have you swapped the left and right cables (input and output)? So that the left channel is on the right on the volume control and vice versa?.
If the popping goes along with it, meaning it's still audible on the left speaker, the L70 isn't the problem.
If you now hear the popping on the right loudspeaker, the L70 is unfortunately the problem and a complaint should be made.

I had to read your response multiple times, it finally made sense. The pop is now on the right side, I guess it's a return for both e and l 70. Not sure I'm up for second chances with this series. Thanks for your help.

 

[Roland68]

I had to read your response multiple times, it finally made sense. The pop is now on the right side, I guess it's a return for both e and l 70. Not sure I'm up for second chances with this series. Thanks for your help.

That's a shame, because the L70 is actually one of the most well thought-out devices on the market. Probably just a simple problem with ground or a solder joint.
Is the pop always the same loud or does it change with the volume?

 

[Biovexo]

That's a shame, because the L70 is actually one of the most well thought-out devices on the market. Probably just a simple problem with ground or a solder joint.
Is the pop always the same loud or does it change with the volume?

The pop's intensity fluctuates, often louder with increased volume but not always. I'm really disappointed. This stack had checked off my needs, now my only option now is to go the d and a 90 route but wanted to avoid that. I don't need the added cost for more power.

 

[Roland68]

The pop's intensity fluctuates, often louder with increased volume but not always. I'm really disappointed. This stack had checked off my needs, now my only option now is to go the d and a 90 route but wanted to avoid that. I don't need the added cost for more power.

There can always be a problem with a device.
Write to Topping's service and include JohnYang1997. Maybe they can tell you something about the problem.
Maybe you just wait 2 weeks until more devices are on the market and there is more experience and order a new L70.

 

[pseudoid]

...@amirm , would you like to respond?...

 

[Atanasi]

Because Amir's SNR measurements are consistently 2dB worse than both manufacturer spec and what Wolf measures

Does Wolf measure SNR at 4 V? Using 5 V would explain the 2 dB difference.

 

[staticV3]

Does Wolf measure SNR at 4 V? Using 5 V would explain the 2 dB difference.

Mojo2: 4.3V vs 4.3V
M500 MKIII: 4.2V vs 4.2V
SU-10: 4.2V vs 4.2V
E70: 4.25V vs 4.25V

As far as I can tell, voltages were the same between Amir and Wolf.
You'll see the same 2-3dB difference with DACs that are limited to 2V btw:


Same voltage, almost 3dB worse DR.

 

[August]

Mojo2: 4.3V vs 4.3V
M500 MKIII: 4.2V vs 4.2V
SU-10: 4.2V vs 4.2V
E70: 4.25V vs 4.25V

As far as I can tell, voltages were the same between Amir and Wolf.
You'll see the same 2-3dB difference with DACs that are limited to 2V btw:
View attachment 245388 View attachment 245389
View attachment 245387 View attachment 245386
Same voltage, almost 3dB worse DR.

With the amirm measuring 22.4khz and the wolfx measuring 20Khz, the extra ultrasonic noise can make a big difference.

 

[staticV3]

With the amirm measuring 22.4khz and the wolfx measuring 20Khz, the extra ultrasonic noise can make a big difference.

That would make sense if all DACs tested by Amir had noise shaping that begins at or below 20kHz.
I don't think even one of the DACs I used for comparison meets that criterion.

 

[Atanasi]

That would make sense if all DACs tested by Amir had noise shaping that begins at or below 20kHz.
I don't think even one of the DACs I used for comparison meets that criterion.

These differences show that practicing science is more than just measuring things. Science includes reporting the methods and ensuring as far as reasonably possible that the results can be replicated by others and make sense with respect to their intended interpretation.

 

[A_T_O_M_I_C_Rooster]

The pop's intensity fluctuates, often louder with increased volume but not always. I'm really disappointed. This stack had checked off my needs, now my only option now is to go the d and a 90 route but wanted to avoid that. I don't need the added cost for more power.

Did you update the firmware on the DAC? There is new firmware for it.

 

[Biovexo]

Sure

Did you update the firmware on the DAC? There is new firmware for it.

Sure did, first thing I did. I've returned both, will have to decide my next move.

 

[AnalogSteph]

Sure sounds like one E70 channel had excessive DC offset for some reason. If the L70's signal path is all DC-coupled from input to volume control, that would result in pops upon changing the volume.

 

[kekotron]

Is there any information out there about the input impedance of this thing? While SMSL pretty much always shares this information in their specs, topping is not that eager to have it in their specsheets.

if anyone is wondering about the input impedance like I did, here's the Topping support response:

 

[Nordling]

Today I received my Topping L70 (ordered at Audiophonics). It is now acclimatizing. What strikes me is that the label on the bottom of the L70 reads "Audio Amplifier Model: TP70A". The box does state that it is "Model L70 BK EU".

 

[DRuszaT]

Today I received my Topping L70 (ordered at Audiophonics). It is now acclimatizing. What strikes me is that the label on the bottom of the L70 reads "Audio Amplifier Model: TP70A". The box does state that it is "Model L70 BK EU".

Read the user manual, Model: TP70A. Solution: the colour of the device and the type of cable vary from package to package.

 

[Nordling]

if anyone is wondering about the input impedance like I did, here's the Topping support response:
View attachment 247002

Thank you. I was wondering what the input resistance is. Especially the balanced single ended input resistance is much lower than the Topping A90, A90D, Pre90.

Model	SE	BAL
Topping A90	10k Ohms	2.0k Ohms
Topping A90D	10k Ohms	2.0k Ohms
Topping Pre90	10k Ohms	2.2k Ohms
Topping L30	2.5k Ohms	-
Topping L70	2.0k Ohms	2.0k Ohms

 

[Veri]

Especially the balanced input resistance is much lower than the Topping A90, A90D, Pre90.

Model	SE	BAL
Topping A90	10k Ohms	2.0k Ohms
Topping A90D	10k Ohms	2.0k Ohms
Topping Pre90	10k Ohms	2.2k Ohms
Topping L30	2.5k Ohms	-
Topping L70	2.0k Ohms	2.0k Ohms

SE input resistance. Right?