Topping NX7 announced

[Tortie]

One last question. Has anyone purchased an NX7? I've seen scarcely any impressions on this product.

 

[Atanasi]

One last question. Has anyone purchased an NX7? I've seen scarcely any impressions on this product.

I have one. I could do some measurements with a Cosmos ADC and its load adapter someday, if you are interested.

 

[Tortie]

So I found a photo of the NX4 DSD DAC. That device used TI opamps. It has three TI1653 for the LPF stage and the driver is TI1688

I have one. I could do some measurements with a Cosmos ADC and its load adapter someday, if you are interested.

So how does it sound and perform? There was an Amazon reviewer that said the NX7 sounded dull and narrowed the stereo field.

 

[Veri]

It's interesting how Topping likes to conceal/hide what's under the hood. The company and it's cherry picked reviewers

It's also peculiar that the NX7 never received a review on ASR. Nearly every Topping product is reviewed here, even previous portable releases.

complain about cherry picked reviews, also complain that it's not reviewed here? Also the op-amps they tend to use are standard choices and more often than not TI, I feel what you're saying there has no real basis unless you have some concrete examples of 'bad' parts used...?

I understand them not showing a lot on their NFCA (Nested Feedback Composite Amplifier) products. Loxjie A10h/A20h are almost exact clones of the Topping L30 circuit. I understand them wanting to protect their intellectual property. If anyone wants to reverse engineer it it's only a matter of time, might as well make it a bit harder to do. Fiio has no real ground breaking amplifier tech to steal lol

 

[Glitch]

The Topping NX7 has a warning that removing the cover automatically voids the warranty. I kinda get the company not wanting customers to tinker with the components and having its designs plastered over the Internet. I don't care if they use cheap components because it measures in the state of art category and is relatively cheap.

Subjectively the NX7 does sound kinda dull until you get used to it because there are no distortions. I have an old headphone amp that sounds more "musical" but it doesn't have the fine detail resolving capabilities of the NX7. The more you crank up the volume on the NX7 the more little details it brings up, there's no resolving wall.

 

[audiofun]

complain about cherry picked reviews, also complain that it's not reviewed here? Also the op-amps they tend to use are standard choices and more often than not TI, I feel what you're saying there has no real basis unless you have some concrete examples of 'bad' parts used...?

I understand them not showing a lot on their NFCA (Nested Feedback Composite Amplifier) products. Loxjie A10h/A20h are almost exact clones of the Topping L30 circuit. I understand them wanting to protect their intellectual property. If anyone wants to reverse engineer it it's only a matter of time, might as well make it a bit harder to do. Fiio has no real ground breaking amplifier tech to steal lol

Topping's NFCA is exactly JDS Element I's headphone amplifier circuit released in 2015, whose layout was significantly improved later and released as the EL Amp and the Atom Amp in 2018. Topping just replaced the buffer from LME49600 to different ones, TPA6120A2 in A90/L30/L50 or OPA1656 in A30Pro, in different products and change the supporting resistor values to make them stable. You can search forum posts of the topping designer johnyang and see how he reverse engineered JDS's products and copy that circuit to his own products. In NX7's case it's buf634a, as mentioned in earlier threads by one owner. I asked the owner for teardown photos and as far as I can see, the circuit is exactly the same as Atom's. Loxjie/SMSL/Sabaj's circuits are also based on Atom's as well. Saying Loxjie/SMSL/Sabaj steal from Topping is not fair, and IMHO is probably just disinformation coming from the latter.

I once emailed JDS boss, John Seaber, and asked what's his opinion about this. He replied "The entire industry shifted and began copying our work after 2018. That's okay. Imitation is flattery." Such kind attitude towards his competitors.

 

[Tortie]

Topping's NFCA is exactly JDS Element I's headphone amplifier circuit released in 2015, whose layout was significantly improved later and released as the EL Amp and the Atom Amp in 2018. Topping just replaced the buffer from LME49600 to different ones, TPA6120A2 in A90/L30/L50 or OPA1656 in A30Pro, in different products and change the supporting resistor values to make them stable. You can search forum posts of the topping designer johnyang and see how he reverse engineered JDS's products and copy that circuit to his own products. In NX7's case it's buf634a, as mentioned in earlier threads by one owner. I asked the owner for teardown photos and as far as I can see, the circuit is exactly the same as Atom's. Loxjie/SMSL/Sabaj's circuits are also based on Atom's as well. Saying Loxjie/SMSL/Sabaj steal from Topping is not fair, and IMHO is probably just disinformation coming from the latter.

I once emailed JDS boss, John Seaber, and asked what's his opinion about this. He replied "The entire industry shifted and began copying our work after 2018. That's okay. Imitation is flattery." Such kind attitude towards his competitors.

Wish I knew what this meant. The BUF634A is just one piece of the puzzle. I don't think its even a driver opamp. It's just used in the boost/buffer stage and with an OPA+BUF topology can deliver a significant amount of current output.

Are you suggesting that the now retired JDS Element I and the NX7 essentially share the same topology with the exception of the BUF634A?

 

[audiofun]

Wish I knew what this meant. The BUF634A is just one piece of the puzzle. I don't think its even a driver opamp. It's just used in the boost/buffer stage and with an OPA+BUF topology can deliver a significant amount of current output.

Are you suggesting that the now retired JDS Element I and the NX7 essentially share the same topology with the exception of the BUF634A?

You are right. BUF634A or other buffers (TPA6120A2, OPA1656) in Topping's other products are just buffers. It can be anything and is not even a main factor. It can even be discrete BJTs. The configuration is OPA+BUF architecture (nested feedback topology or composite amplifier in this case) is the real key factor to make it performs well.

The similarity does not end here. Some other products also use OPA+BUF as composite amplifier, such as Matrix Element X, Benchmark DAC3, THX based amps, or Geshelli products. JDS' topology is very special in that it's the first time transitional miller compensation (TMC) is applied to a headphone amp to make it super well performing. The TMC is configured in a way that the compensation is also enclosing the input stage. Topping copied JDS' TMC topology entirely. JDS ELAmp/Atom/Elements, Topping A90/L30/A30Pro/NX7/DX5/EX5/DX3Pro+, SMSL's M500MKII, Sabaj's A10d/A20d/A10a/A20a share the same circuit (TMC that enclosing input stage) except the buffer used.

JDS' performance is not achieved in one day. Original Element I (2015) has the same circuit as JDS Atom (2018) but the former performs much worse than the latter, although in 2015 it was super, super good already. The key to make TMC performs well, according to JDS, is the new layout that achieved super low noise and distortion. Topping largely copied JDS Atom's layout as well.

Another way to understand the situation --- Benchmark DAC3 and JDS Atom both use the LME49600 buffer wrapped with an op amp and formed a composite amplifier. They are both OPA+Buf but have very different topology. Topping/SMSL/Sabaj on the other hand, use the same circuit and layout as JDS Atom. The only thing different is the buffer used by Topping/SMSL is not LME49600, which could be anything and not important, as proofed by topping's various NFCA products.

 

[Tortie]

You are right. BUF634A or other buffers (TPA6120A2, OPA1656) in Topping's other products are just buffers. It can be anything and is not even a main factor. It can even be discrete BJTs. The configuration is OPA+BUF architecture (or nested feedback topology) is the real key factor to make it performs well.

The similarity does not end here. Some other products also use OPA+BUF, such as Matrix Element X, Benchmark DAC3, THX based amps, or Geshelli products. JDS' topology is very special in that it's the first time transitional miller compensation (TMC) is applied to a headphone amp to make it super well performing. The TMC is configured in a way that the compensation is also enclosing the input stage. Topping copied JDS' TMC topology entirely. JDS ELAmp/Atom/Elements, Topping A90/L30/A30Pro/NX7/DX5/EX5/DX3Pro+, SMSL's M500MKII, Sabaj's A10d/A20d/A10a/A20a share the same circuit (TMC that enclosing input stage) except the buffer used.

JDS' performance is not achieved in one day. Original Element I (2015) has the same circuit as JDS Atom (2018) but the former performs much worse than the latter, although in 2015 it was super, super good already. The key to make TMC performs well, according to JDS, is the new layout that achieved super low noise and distortion. Topping largely copied JDS Atom's layout as well.

Another way to understand the situation --- Benchmark DAC3 and JDS Atom both use the LME49600 buffer wrapped with an op amp and formed a composite amplifier. They are both OPA+Buf but have very different topology. Topping/SMSL/Sabaj on the other hand, use the same circuit and layout as JDS Atom. The only thing different is the buffer used by Topping/SMSL is not LME49600, which could be anything and not important, as proofed by topping's various NFCA products.

@audiofun, this is an incredibly detailed overview of the design history and topologies of these various devices. Thank you for sharing this information.

 

[tifune]

Hoping someone can clarify for me, input sensitivity on this is 4V for M gain and 13V for L gain. But, it looks like input is a 3.5 SE connection. The vast majority of devices outputting 4v+ are balanced, so presumably I'd need a converter cable? I'd like to use my Qudelix's balanced out, 2.5mm. so would that be a 2.5 to 3.5 balanced, or a 2.5 balanced to 3.5 SE cable?

I emailed topping already, but historically sometimes they answer, sometimes they don't, so thought I'd ask here, too.

 

[staticV3]

The vast majority of devices outputting 4v+ are balanced, so presumably I'd need a converter cable?

All passive Bal->Unbal converters will cut the output voltage in half. There are some active converters which will do 4Vrms Bal -> 4Vrms SE, but I doubt they'd be practical for an on-the-go setup.

I'd like to use my Qudelix's balanced out, 2.5mm.

Only Bal sources with a GND pin can be converted to SE (by just leaving out- disconnected and using the GND as signal return instead.

You may be able to use the 5K's 2.5's Out+ as Signal and its 3.5 GND as signal return (such Adapters exist), but you'd be left with a signal amplitude no stronger than the 3.5 out on its own.
In fact, there's a good chance that performance would even be worse than just using the 3.5 out.

 

[Veri]

Hoping someone can clarify for me, input sensitivity on this is 4V for M gain and 13V for L gain. But, it looks like input is a 3.5 SE connection. The vast majority of devices outputting 4v+ are balanced, so presumably I'd need a converter cable? I'd like to use my Qudelix's balanced out, 2.5mm. so would that be a 2.5 to 3.5 balanced, or a 2.5 balanced to 3.5 SE cable?

I emailed topping already, but historically sometimes they answer, sometimes they don't, so thought I'd ask here, too.

The 4.4mm is there for convenience and minimal gain in crosstalk. The input is 3.5mm single ended, you can't route a balanced output into that since there aren't enough pins in a standard 3.5mm to make that possible (there exists a niche 3.5mm balanced connector but that's not what is used here).

 

[wacomme]

Yes.


Make sure you have the A2049 version of the dongle with the full 1.0Vrms and make sure you're getting the full 1.0Vrms with a 60Hz, 0dBFS sine wave audio file and a basic multimeter.

Is model A1619 lacking? That's what I received from Amazon.

 

[staticV3]

Is model A1619 lacking? That's what I received from Amazon.

?
This is Apple A1619:

 

[wacomme]

?
This is Apple A1619:
View attachment 208432

Correct. That is what I'm using for my iPhone or iPad connection.

 

[tifune]

The 4.4mm is there for convenience and minimal gain in crosstalk. The input is 3.5mm single ended, you can't route a balanced output into that since there aren't enough pins in a standard 3.5mm to make that possible (there exists a niche 3.5mm balanced connector but that's not what is used here).

Given that, just for my on curiosity, any idea which device(s) output 13v SE? I would think if you already have such a device, the NX7 wouldn't be needed in the first place

 

[wacomme]

How does the Qudelix K5 and the Hidezs S9 Pro, also portable devices, compare to the NX7? For overall performance, which is most useful? I presume it's the Qudelix K5 since it has PEQ. Now, for portable desktop use, that may change to be the NX7.

 

[Tortie]

Topping has non-existent customer support. I emailed them too with a question on the NX7. Never heard back from them.

Poor customer support and a failure to respond to inquiries doesn't sit well with me. And who can forget the L30 debacle?

With JDS, Schiit and Geshelli I've always received prompt replies to my emails.

 

[Veri]

Given that, just for my on curiosity, any idea which device(s) output 13v SE? I would think if you already have such a device, the NX7 wouldn't be needed in the first place

Correct. But you ask because the specs say maximum 4V for M gain and 13V for L gain right? It is just to indicate when the output stage is overloaded, it's not a contest to then actually overload it

I have an older device at home with pre-amp that goes up to 5Vrms in single ended. So that would make it clip in M at maximum voltage in. I think the Drop THX 789 overloads in high gain at 4V or so, so at balanced input high gain starts to clip at the end of its range. It's just good info to know.

 

[Tortie]

If you look at AliExpress, eBay and Amazon Marketplace it is evident that sales for the NX7 are soft as Charmin. The product is not selling. On AlliExpress NX7 listings show the number of units sold and their extremely low compared to other Topping products. eBay has similar metrics that paint a similar picture of poor sales for the NX7. Amazon also shows very few reviews for the NX7 compared to other Topping products.

It's clear that this product is not selling well. In fact you could deem the NX7 as Dead On Arrival.

This could be th result of a number factors:

1) general weak demand for amp only portables
2) bulkiness
3) overpriced
4) accelerated trend of work from home