Topping L30 Headphone Amplifier Review

[EHC]

No. For an OPA1612 to suffer that kind of damage requires a voltage on the input pins 500mV+ greater than the supply voltage. Section 7.3.2 of the TI data sheet (https://www.ti.com/product/OPA1612) address this specifically. Voltages like that can't come from the output, because that's limited to the supply voltage, unless the schematic is very wrong. The point about ESD is that it can easily be greater than the supply voltage. Which is how the mango hits the fan.

Best practice would be to have two resistors - one grounding, and another in series with the input to limit fault current to less than 10mA.

The resistors in the feedback loop can not limit the current under 10mA. Normally, no voltage difference can develop between TPA output and OPA inverting input, but in an unstable transitory regime, with the noninverting input in the air...

 

[sandymc]

The resistors in the feedback loop can not limit the current under 10mA.

They don't have to. The input connected to the potentiometer is vulnerable to ESD because the potentiometer can be touched.

 

[dgnzcn]

Decided to open my new 201262xxx L30 on a whim to see what the fix looks like even though I heavily suspected it's there, this is what it looks like:

That looks very clean and unlike some of the other photos, I imagine this might be how they come out of the factory so maybe my board was made like this already, which would be cool. Maybe some day when I'm brave enough I'll open the front as well to give you a photo of the revised 2011+ L30 circuit and to try to see if there's anything I can do about that horrendous volume pot is there a possibility of developing larger channel imbalance by removing and putting the pot back on?

I think the yellow metal pin in the front left was just inserted, don't you think it was made very amateur?

 

[companyja]

I think the yellow metal pin in the front left was just inserted, don't you think it was made very amateur?

Not really, the unit is aesthetically the same from the outside and the execution is very clean. Grounding is a simple concept, if you need it grounded just have it touch the outside of the case. It reminds me of record players and their wiring - literally the manufacturer standard solution was and probably still is to have three wires coming out of the record player - two RCA outs and a ground wire with an exposed spade that you jam into the back of the amplifier/reciever to touch its massive case. This pin is much cleaner than if they had soldered a wire in there that goes to the outside of the case and is jammed below one of the screws - that would be amateur.

 

[dgnzcn]

Not really, the unit is aesthetically the same from the outside and the execution is very clean. Grounding is a simple concept, if you need it grounded just have it touch the outside of the case. It reminds me of record players and their wiring - literally the manufacturer standard solution was and probably still is to have three wires coming out of the record player - two RCA outs and a ground wire with an exposed spade that you jam into the back of the amplifier/reciever to touch its massive case. This pin is much cleaner than if they had soldered a wire in there that goes to the outside of the case and is jammed below one of the screws - that would be amateur.

Maybe..., But i would still expect a more original strongest solution, it seems that simple and unsafe.

 

[Quomz]

Maybe..., But i would still expect a more original solution, it seems that simple and unsafe.

This is to provide a ground path via case and therefore RCA shield as far as I understand, not sure if for an EE this is something that needs an "original solution". What's your less simple and less unsafe suggestion?

 

[dgnzcn]

Maybe ... but I would still expect a fabricated powerful solution, it looks so simple and insecure.

 

[companyja]

Modifying the circuit is the last thing you want to do if inserting a pin that touches the chassis is sufficient.

1) All these devices have some sort of grounding protection built-in, the L30's was insufficient. Having the circuit be connected to the chassis is a lot more reassuring than knowing they just redesigned the circuit in hopes it would work this time.

2) Modifying the circuit board can impact performance, on a small amp like this the components are bunched together and the printed board is probably a few layers deep. I don't want them messing with the performance of the amplifier if they can just do this. For example, the DX3 Pro was revised to have better protection and as a result the output impedance of the 6.3mm jack was moved up from 1 to 10 ohm. This has deterred some people from getting a v2 unit.

Now will this be sufficient? I don't know, I hope so, we can see that some L30 have still failed. We'll need to see if the trend continues. At least no more headphones have been reported fried by the L30 to my knowledge since the DC protection fix

 

[half_dog]

No. For an OPA1612 to suffer that kind of damage requires a voltage on the input pins 500mV+ greater than the supply voltage. Section 7.3.2 of the TI data sheet (https://www.ti.com/product/OPA1612) address this specifically. Voltages like that can't come from the output, because that's limited to the supply voltage, unless the schematic is very wrong. The point about ESD is that it can easily be greater than the supply voltage. Which is how the mango hits the fan.

Best practice would be to have two resistors - one grounding, and another in series with the input to limit fault current to less than 10mA.

 

[Jose Hidalgo]

I think the yellow metal pin in the front left was just inserted, don't you think it was made very amateur?

This is the inside of a high-end tube amplifier, with only cabling, almost no PCBs. Don't you think it was made very amateur ?

Maybe ... but I would still expect a fabricated powerful solution, it looks so simple and insecure.

Nobody is ever supposed to open a L30. EVER. So as long as there is contact, the problem is solved, nicely and effectively. You would be surprised at the things you can see when you open supposedly high-end devices.

 

[dgnzcn]

This is the inside of a high-end tube amplifier, with only cabling, almost no PCBs. Don't you think it was made very amateur ?

View attachment 117859


Nobody is ever supposed to open a L30. EVER. So as long as there is contact, the problem is solved, nicely and effectively. You would be surprised at the things you can see when you open supposedly high-end devices.

Haha this is incredible , there is no circuit schema on the ground

 

[EHC]

They don't have to. The input connected to the potentiometer is vulnerable to ESD because the potentiometer can be touched.

ESD vulnerability is just a consequence. There are a lot of devices, including headphone amplifiers, with "potentiometer that can be touched". No problem at all.

The real cause is OPA1612 noninverting input "in the air" when an imperfect contact at the potentiometer cursor occur.

Don't get me wrong, I consider L30 a wonderful amplifier at a good price. The design is simple, elegant and innovative. But you cannot bet on potentiometers reliability. A simple resistor between OPA noninverting input and ground (two, actually, one per channel) could have avoided all this trouble.

 

[FedHal]

I already compensated for Jimbob54's burnt headphones. And he's happy. No other guy has come to me for compensation yet.
What do you know?

Hello, I did not enter the forum for several days, after my last publication I read this that you published.
I have tried to get Aliexpress to honor the warranty on my takstar pro 82 that have been burned from using them with my old L30 unit. I have not been successful asking for the warranty for several months, I have already tired.
You say that it is possible that I will be rewarded for my burned headphones for using them with L30?
I am from Argentina and it is difficult to get my takstar pro 82 again.
I'm using a translator, sorry.
Greetings!

 

[Tup3x]

Just received my replacement unit today. That was a long wait but it's finally back.

I must say that Topping's apology letter probably doesn't help (in fact, it does the opposite...). I'd highly appreciate it if manuals, website and other documents would be translated properly (by actual translator) and use proper langue. This just isn't professional.

I appreciate how Topping handled this but they really should put more thought in their written material.

 

[companyja]

I have an MA in English Language and Literature and will gladly proof-read and correct any and all Topping press statements/advertising material in exchange for a hot new DAC or AMP every once in a while

 

[Wagstaff]

Free worries. Just what we all want

 

[threni]

I'd highly appreciate it if manuals, website and other documents would be translated properly (by actual translator) and use proper langue. This just isn't professional.

Sorry, I had to laugh.

Besides, I often read people saying this or that thing isn't "professional" where it's neither professional or unprofessional. It's irrelevant. They're a small company which makes great products. The grammar/spelling on a letter apologising for a problem will dissuade precisely no-one from buying future products. Imperfect English is fairly common for a lot of stuff from China. Their website has some howlers - the E30 page describes it as:

A "small hot hatch" like DAC

which combines meaninglessness with poor grammar. But it just comes across as charming. The exact same sort of thing I'd do if I had to produce some text in a foreign language!

"Are you sure that's correct and idiomatic?"
"Who gives a **** - it's lunchtime! Let's go"

 

[Vini darko]

My personal favorite from the fun folks at blon.

Newer products have had this fixed unfortunately.

 

[ngs428]

Just received my replacement unit today. That was a long wait but it's finally back.

I must say that Topping's apology letter probably doesn't help (in fact, it does the opposite...). I'd highly appreciate it if manuals, website and other documents would be translated properly (by actual translator) and use proper langue. This just isn't professional.
View attachment 117898
I appreciate how Topping handled this but they really should put more thought in their written material.

I never got a letter.. I didn’t need the free worries anyway.

 

[dgnzcn]

Just received my replacement unit today. That was a long wait but it's finally back.

I must say that Topping's apology letter probably doesn't help (in fact, it does the opposite...). I'd highly appreciate it if manuals, website and other documents would be translated properly (by actual translator) and use proper langue. This just isn't professional.
View attachment 117898
I appreciate how Topping handled this but they really should put more thought in their written material.

What is the serial number about of the L30?,
Even if they have grammatical mistakes, I think it is a gesture for them to think about it and send it.