Topping L30 Headphone Amplifier Review

[JohnYang1997]

@JohnYang1997
Can you please explain which improvements were made on the board?
This to know if I can sleep calmly on my post-2012 L30 (if I get the replacement) or if I should wait for february batch to be out.

Plus: is the E30 completely free from issues or ESD problems that could be trasmitted to the amp through RCA ports?

I'll be waiting for your reply for the final decision.

Unfortunately John still doesn't know what is causing these issues. The december protections have been implemented "in the blind", because nobody has been able to replicate the ESD issues in a lab. So nobody can say that the L30 is completely free from these issues. I for one will wait for the february batch, unless John clearly states otherwise.

As for the E30, AFAIK there haven't been any fried E30s yet, so I guess we can safely say that the E30 is completely free from these issues.

The point is to prevent headphones from being damaged. If headphones are safe, that's what matters right?

 

[Pdxwayne]

I received your PM, but we have purchased testing equipments.
The thing is the whole thing is floating/isolated from earth on its own. But when the RCA is connected the thing is earthed. This way creats a path for ESD current to flow. There are two potential fixes. One is to beaf up the inputs. Another is to manually creat a predetermined ESD current path. Maybe a combination of both.

What if the laptop and DAC have no earth either? Will L30 still earthed if connected via RCA to DAC?

 

[JohnYang1997]

What if the laptop and DAC have no earth either? Will L30 still earthed if connected via RCA to DAC?

That should be better will have to test about that.

 

[JohnYang1997]

I fully agree with solderdude here.

According to a schematic of the input circuit, which someone put on the web some time ago, the wipers of the potentiometer go straight to the OPA1612 inputs. This is good for noise reasons, but dangerous in terms of ESD. Especially since the metal part around the shaft is not connected to ground.
If only Topping had used a potentiometer from the RK09L series and connected the ground pins to ground on the PCB.

Some have suggested to ground the L30. This may actually make the problem worse, since it will provide a solid return path for the ESD spark. The ESD spark can easily find a path around the volume knob, hit the shaft, move further to the wipers of the potentiometer with a small spark (internally in the potentiometer or externally) and thereby hit the inputs of the OPA1612.

The OPA1612 has ESD ratings of +/- 3 kV (human body model) and 200 V (machine model), which should be OK for handling what it will be subjected to during production, but far from sufficient if it is hit by a high voltage ESD spark.
I have been involved in a lot of electronic designs, which were tested with 8 kV contact discharge and 16 kV air discharge. This is fairly standard.

It is very disappointing that Topping has not done ESD tests before releasing the product. I agree with JohnYang1997 that the ESD test equipment is relatively expensive, as he wrote "It's neither cheap nor easy to get". I don't think it it too hard to get though and it could be a lot more expensive not to buy it and do proper testing.

I also did wonder about the old fashioned transformer and whether that was leagal at all, as someone hinted at previously. The standby consumption is way higher than it should be.

So where did the CE-mark come from?

I own an L30 and I do like the performance, but these basic flaws should have been eliminated before it was released to the market.

I have addressed this issue. But here we are.
In house testing and out sourced testing are different. Everything is tested for parameters and regulations before released. That's true.
But when we are talking about ESD problem in real world and reproduce it in our own lab. It's very different. The thing is from the regulation it only needs to pass 4kV to 8kV. When in real world it can go up to 20kV to 50kV.
And we have to understand these are not basic stuff. You can just ground the chassis and call it a day. But in some cases like this one is not that simple. To get to the end of this, it requires a lot of deeper knowledge and investigation. But on the other hand you can prevent this using some extra components willy nilly. But how many things are like this? You can't just foresee all the issue and just smash everything onto the board. That doesn't happen.
The main issue is not ESD but the potential harm to headphones. Preventing that from happening, and everything else don't really matter that much do they?

 

[Roland68]

I received your PM, but we have purchased testing equipments.
The thing is the whole thing is floating/isolated from earth on its own. But when the RCA is connected the thing is earthed. This way creats a path for ESD current to flow. There are two potential fixes. One is to beaf up the inputs. Another is to manually creat a predetermined ESD current path. Maybe a combination of both.

As long as the housing has no electrical contact with the device, that shouldn't be a problem. This is the solution for many devices (e.g. Atom).

I think that this special constellation with the screwed potentiometer and the anodized aluminum housing parts (anodized is good insulation) is the real problem.

If the potentiometer happens to have electrical contact with the housing parts (nut, scratches, anodized too thin), an ESD pulse could penetrate the signal lines and suddenly overdrive the 1612.

That would explain why it only affects so few devices, no headphones have to be connected and no audio signal had to be present.

I may be wrong, but an enclosure should either be properly grounded or completely isolated.

If the L30 is connected to an E30 with chinch and the E30 with Toslink, there is also no grounding.

 

[ninetylol]

That should be better will have to test about that.

Can i order a A50s or should i wait for another revision there too? Thanks in regards!

 

[JohnYang1997]

Can i order a A50s or should i wait for another revision there too? Thanks in regards!

A50s is mostly fine. No issue reported.

 

[Vini darko]

@SHENZHENAUDIO thankyou for the fast response and dispatch of my replacment L30 through amazon. Great service I won't hesitate to buy from you again

 

[JohnYang1997]

As long as the housing has no electrical contact with the device, that shouldn't be a problem. This is the solution for many devices (e.g. Atom).

I think that this special constellation with the screwed potentiometer and the anodized aluminum housing parts (anodized is good insulation) is the real problem.

If the potentiometer happens to have electrical contact with the housing parts (nut, scratches, anodized too thin), an ESD pulse could penetrate the signal lines and suddenly overdrive the 1612.

That would explain why it only affects so few devices, no headphones have to be connected and no audio signal had to be present.

I may be wrong, but an enclosure should either be properly grounded or completely isolated.

If the L30 is connected to an E30 with chinch and the E30 with Toslink, there is also no grounding

Thanks for the reply. First get to the E30 part. Yes the toslink will isolate the thing. And if the pc is isolated like some laptops it's fine too.
You are correct about properly grounded or completely isolated. Yet it's apparent some picture showed the input trace got jumped. But when I measure the metal part on the pot is also not connected to the pins electrically. Well sure the isolation must be poor but you get the idea.
ESD will find its way through the shortest path to the earth right? If you think about it, it takes quite a lot to travel through 1612. Another issue is mentioned by @solderdude, input resistance is quite low for best noise performance. If I increase the resistance the current may find another way to flow. Hence the second solution I mentioned. Creating a predetermined path for ESD current such that the current won't flow through the components.
The other thing is, if you take things like this out and focus on it, a lot of engineering can be done to it. Were it not for yhe failure, such investigation will not happen.
As a side note, O2, El Amp, El dac series, magni, magnius and a few others all have similar design yet no major issue. I wonder why that's the case.

 

[ninetylol]

A50s is mostly fine. No issue reported.

So the changes to L30 in 2012 badge in regards to dc protection is already made to A50s? I just want to be sure. Also want to keep supporting Topping for your transparency!

 

[JohnYang1997]

So the changes to L30 in 2012 badge in regards to dc protection is already made to A50s? I just want to be sure. Also want to keep supporting Topping for your transparency!

Yes. And the fact that many products don't have dc protection circuit and people still use them and love them, to me if there's no reported issue it's fine.

 

[jei]

Ordered L30 on 23 November from Shenzen Audio thru Amazon.de. Serial 2010. After reading about the problems here I was a bit afraid for my headphones and also for connected active monitors. It's -20°C here atm and static electricity is par for the course. If DC-protection is working with 2012 models that's good enough for me in this price category I guess. Shenzen Audio sent a replacement in less than 24 hours after contact, thumbs up for that.

 

[ninetylol]

Yes. And the fact that many products don't have dc protection circuit and people still use them and love them, to me if there's no reported issue it's fine.

Thanks i just ordered a A50s. Hope to pair it with the New D30pro if it comes soon

 

[SHENZHENAUDIO]

@SHENZHENAUDIO thankyou for the fast response and dispatch of my replacment L30 through amazon. Great service I won't hesitate to buy from you again

That's what we should do. Thank you as well, mate.

 

[Jose Hidalgo]

The point is to prevent headphones from being damaged. If headphones are safe, that's what matters right?

The point is to prevent headphones AND L30 from being damaged.
If the 2012 revision prevents headphone damage but ESD can still damage my two L30 and I need to buy two new ones, I guess that's not OK.
I don't know if I should exchange my two L30 (which I love) or pay a bit more and get two A50s instead. I need to think.

 

[JohnYang1997]

The point is to prevent headphones AND L30 from being damaged.
If the 2012 revision prevents headphone damage but ESD can still damage my two L30 and I need to buy two new ones, I guess that's not OK.
I don't know if I should exchange my two L30 (which I love) or pay a bit more and get two A50s instead. I need to think.

You can get replacement if it fails. That has always been the case.

 

[Roland68]

Thanks for the reply. First get to the E30 part. Yes the toslink will isolate the thing. And if the pc is isolated like some laptops it's fine too.
You are correct about properly grounded or completely isolated. Yet it's apparent some picture showed the input trace got jumped. But when I measure the metal part on the pot is also not connected to the pins electrically. Well sure the isolation must be poor but you get the idea.
ESD will find its way through the shortest path to the earth right? If you think about it, it takes quite a lot to travel through 1612. Another issue is mentioned by @solderdude, input resistance is quite low for best noise performance. If I increase the resistance the current may find another way to flow. Hence the second solution I mentioned. Creating a predetermined path for ESD current such that the current won't flow through the components.
The other thing is, if you take things like this out and focus on it, a lot of engineering can be done to it. Were it not for yhe failure, such investigation will not happen.
As a side note, O2, El Amp, El dac series, magni, magnius and a few others all have similar design yet no major issue. I wonder why that's the case.

I think it could be because of this particular pot.
The housing of the potentiometer has no contact with ground, but the potentiometer housing and axis are in contact.

You can simply connect an L30 to the power supply unit and introduce an ESD pulse into the thread or the axis of the potentiometer.

If that is the mistake, your other efforts will not work. As long as you don't have a "real" grounding (on the housing), where should the ESD path lead?
If you have a grounding, use a potentiometer with a ground connection on the housing.
Safe isolation of the potentiometer from the housing and a plastic potentiometer knob would then also protect the current devices.

As I said, I'm only talking about the case of the ESD impact in the potentiometer.
Perhaps the signal lines from the potentiometer to the 1612 are the least resistance. It would just explain all the phenomena, including the broken conductor tracks. The 1612 will probably burn down at this point because it is drawing too much current from the power supply due to the high DC voltage at the inputs.

Our devices, and those of our customers, all run in the range of kV and kA. The devices that are operated on the mains are completely earthed. All devices with batteries or external power packs are completely isolated.

 

[JohnYang1997]

I think it could be because of this particular pot.
The housing of the potentiometer has no contact with ground, but the potentiometer housing and axis are in contact.

You can simply connect an L30 to the power supply unit and introduce an ESD pulse into the thread or the axis of the potentiometer.

If that is the mistake, your other efforts will not work. As long as you don't have a "real" grounding (on the housing), where should the ESD path lead?
If you have a grounding, use a potentiometer with a ground connection on the housing.
Safe isolation of the potentiometer from the housing and a plastic potentiometer knob would then also protect the current devices.

As I said, I'm only talking about the case of the ESD impact in the potentiometer.
Perhaps the signal lines from the potentiometer to the 1612 are the least resistance. It would just explain all the phenomena, including the broken conductor tracks. The 1612 will probably burn down at this point because it is drawing too much current from the power supply due to the high DC voltage at the inputs.

Our devices, and those of our customers, all run in the range of kV and kA. The devices that are operated on the mains are completely earthed. All devices with batteries or external power packs are completely isolated.

That's all correct. But every case is a little special.
To reply to my efforts will not work. If the upstream and downstream devices are all isolated it's fine. If there's ground, isn't it best to lead the ESD to reservoir cap to absorb all the energy? There will always be solutions, some dirty ways, some cleaner ways. Thank you for your reply, I'll share when I make it ESD proof.

 

[Azeendeen]

So ummm guys, coming from a commercial buyer with no knowledge of anything electronic and not understanding all the jargon. What topping says is basically units with S/N 2012 and higher won't have any problems right? Because my Amazon seller just asked me if I wanted a replacement or refund. Im assuming go for the replacement, since the newer units are safe right?

 

[JohnYang1997]

So ummm guys, coming from a commercial buyer with no knowledge of anything electronic and not understanding all the jargon. What topping says is basically units with S/N 2012 and higher won't have any problems right? Because my Amazon seller just asked me if I wanted a replacement or refund. Im assuming go for the replacement, since the newer units are safe right?

Basically, yes.