Topping L30 Review and Measurements

Now this is kind of super duper funky. The R channel seems totally off. Is Topping suffering from Soncoz syndrome? Did I get a bum unit? Note that we didn't catch this before because the levels in the Triple Sine Dashboard were too low, at the cusp of the deviation between L and R channels.

Topping L30
THD+N vs power
32 ohm load, 1kHz, 90kHz bandwidth


Let's confirm via FFT. Push this up to 2Vrms.

Topping L30
1kHz 2Vrms 32 ohm load


Yep confirmed. At higher voltages, the R channel (red) is completely out of whack with the left channel (blue). This is troubling. I DO NOT RECOMMEND! LOLZ!



To be honest, I really wish I hadn't seen this. These are the kind of things that make people think that gear made in China is cheap or that China cannot make good stuff - which is not true at all. It should be noted that since the Changstar days, everyone knows I've been a magnet for "defective" gear. Or maybe I'm the anti-Amir where stuff he shills happens to have measurement anomalies. Funny how this happens. This is two out of two now with respect to peer-review of ASR measurements of gear the topping of the heap.

 

Well, it turns out that the behavior only happens with the 32-ohm load. The 300-ohm load is perfect. This makes total sense now with respect to the Triple Sine Dash because it doesn't get anywhere near 2Vrms for the 32-ohm headphones. The R channel seems current started for lower impedance loads which ask for the electrons.

Topping L30
THD+N vs power
300 ohm load, 1kHz, 90kHz bandwidth

 

I'm done here. This was a waste of my time. I'd be happy if anyone has another L30 to send to me so I can chalk this off as a defective unit. (Actually I got one more measurement, the potentiometer tracking...)

 

If that's you in the photo, it could be because we are old school have heard things from the past (actually not so recent past) that sounded better than these new trendy "state of the art" designs. It's becoming obvious where the disconnect lies. It's generational - having exposure to certain kinds of gear - and cost cutting, simplification. Also, no one knows how to design discrete anymore.

I didn't see it as calling it out. The point is that confirmation bias works both ways. For certain I am guilty of this - and this is why I really like doing blind tests, mostly informal because of speed and ease, and at times formal double-blind level matched to a mV.

To more seriously answer your question: it's not just the global negative feedback. It's actually the TPA6120 output device in a Nested Composite Feedback loop. We've seen this part used in quite a few other amp designs and they all do sound very similarly to my ears. Contrary to how well a single steady sine wave (or two sine waves) may measure, different parts will sound different.

For example, for fun I replaced the Modi 3+'s output amp OPA1688 with an OPA1656 because I wanted to change the sound from one that "fat" (fun and happy was an intentional voicing) to one which was more neutral (serious). Regardless, the Modi+ still measures with 110db SINAD at 0fbFS and from a cursory look, the same distortion pattern.

 

I have a bone to pick with how ASR does this. The 2V into an HD650 won't be fatal, at least for a short duration. A longer duration could cause the voice coils to heat up and melt. The issue which I have is that transducers pushed to this level will distort massively. Magnitudes. Not one order or two orders. More like six to nine orders of magnitudes higher distortion. That is up to x1000000000. This is going to mask any distortion from the DAC or amp. Despite the defect, at 2Vrms, we would still be under 0.005 THD+N. That's darn low.

ASR is hearing the headphone distort. Not the amp. ASR uses tales of "I cranked it up and heard distortion" as anecdotes to support his narrative. He has also shown no ability to hear the massive THD+N of the plate amps of the JBL LSR305 powered monitors in his very positive review of it.

We do not. Statistics tell us that we should sample more. 30 units for a 90% confidence level? However much I think that Topping rep John Yang at ASR is dickhead because he loves to shit on competitors products and would utterly love to take the low road like Amir, I will not. We need to give Topping the benefit of the doubt. Of course seeing what's happened with the Soncoz DAC's measurement irregularities, this becomes a bit more difficult.

We can laugh, we can shake our heads, we but still need to be fair.

 

No reason at all, especially at these new set of realistic voltage levels per @atomicbob's suggestion: 0dBu, -10dBu, -20dBu. Lemme get back and redo the TripleX Sin Panel with the HD650 and Grado SR225X as the loads. Now at 2Vrms (+8.23dBu) I would hesitate. The drivers of the Focal headphones will slam well before 2Vrms. The Grados would probably catch on fire given their sensitivity.

The board has a nice provision to use real headphones as loads already.


The panel in the first post is still experimental. Maybe I should use real loads? Sorry, I'm such a geek addicted to fun and learning that I can't turn this suggestion down.

 

Just get rid of the current rows and use the four headphones that you suggested. Add a CFA IEM or HE6se row when the amp is suited for it.

Nothing beats using more realistic tests with measurements.