Topping L30 Headphone Amplifier Review

[EHC]

I just completed (it was in a long queue !) adding my own ESD fix to the "retired" early batch unit I was left with after the Amazon seller replaced my L30 last year. Very simple; just dremeled away the paint inside the inner case where the volume pot nut screws down, added a solder lug and washer to the pot shaft, soldered a short wire between it and the ground point via beside the rear RCA and screwed everything back together tightly. Measured and now seeing dead short between RCA shields and the aluminum case or pot shaft.

Works perfectly...absolutely no difference between sound of this one and my "factory fixed" unit with the pogo. 20 mins of work and 2 X L30's for the price of one......I won't ever sell the DIY fixed unit of course, but I'm quite happy to run my HD650's off it in my home office....it will be totally fine now.

I think your headphones are still at risk. In my humble opinion, ESD vulnerability is just a consequence. The fundamental cause is OPA1612 noninverting input "in the air" when an imperfect contact at the potentiometer cursor occur. The cure is a simple resistor between OPA noninverting input and ground (two, actually, one per channel, 22k-100k). The replacements come with modified protections to, wich is nice.

 

[JohnYang1997]

I think your headphones are still at risk. In my humble opinion, ESD vulnerability is just a consequence. The fundamental cause is OPA1612 noninverting input "in the air" when an imperfect contact at the potentiometer cursor occur. The cure is a simple resistor between OPA noninverting input and ground (two, actually, one per channel, 22k-100k). The replacements come with modified protections to, wich is nice.

Not necessarily true.

 

[Roland68]

An ESD safe design doesn't require ground earthing of connected input and output devices as you imply, it generally means ensuring that introduced ESD pulses are directed away from paths which could take them into the most sensitive circuits (like the output opamps).

Maybe I wasn't paying attention somewhere, do you have more information?
So far, I was only aware of protective grounding, functional grounding and equipotential bonding systems. Alternatively, the best possible insulation against the voltage breakdown.
Maybe you have a link to it?

 

[JohnYang1997]

Maybe I wasn't paying attention somewhere, do you have more information?
So far, I was only aware of protective grounding, functional grounding and equipotential bonding systems. Alternatively, the best possible insulation against the voltage breakdown.
Maybe you have a link to it?

Basically. The earth connection is from the upstream. So the ESD current flows from hand to chassis to input ground to the upstream device to the earth.

If the upstream is also isolated. Then there shouldn't be any discharge before very high ESD voltage. Then the ESD current will likely flow through the transformer and to the mains.

 

[Roland68]

If the upstream is also isolated. Then there shouldn't be any discharge before very high ESD voltage. Then the ESD current will likely flow through the transformer and to the mains.

I don't really know that much about ungrounded devices, we don't have anything like that. That would also be too dangerous.
I assumed if no ground exists, the ESD strike would follow the path of gerinsten resistance or the greatest potential difference and inject capacitive and inductive to the electronics.

 

[JohnYang1997]

I don't really know that much about ungrounded devices, we don't have anything like that. That would also be too dangerous.
I assumed if no ground exists, the ESD strike would follow the path of gerinsten resistance or the greatest potential difference and inject capacitive and inductive to the electronics.

If there's no ground to flow to then there's no issue. The harm of ESD is basically the dissipation of energy in the wrong place. You either cut the flow or direct the current to the safe route.
Think of planes, were there any issue in operation?

 

[Roland68]

If there's no ground to flow to then there's no issue. The harm of ESD is basically the dissipation of energy in the wrong place. You either cut the flow or direct the current to the safe route.
Think of planes, were there any issue in operation?

In fact, the ESD problems in aircraft have become significantly greater in recent years, as more and more composites and plastics are used.
As a result, the test criteria for our customers' products have been tightened up. Fortunately not for our products .
But that's another topic.
Thanks for the explanation John, I like to learn.

 

[SaberCat]

In fact, the ESD problems in aircraft have become significantly greater in recent years, as more and more composites and plastics are used.
As a result, the test criteria for our customers' products have been tightened up. Fortunately not for our products .
But that's another topic.
Thanks for the explanation John, I like to learn.

Further to all the above, static charges (i.e. excesses or deficiencies of electrons on one thing relative to another) accumulate on insulated bodies due to friction thjrough movement (mainly)...ie the so called triboelectric effect. They will simply redistribute across what is now a connected system when one charged object touches another which has a conductive capability unless a ground path exists ; if no current flows towards ground then the total charge on the system remains the same but spreads to reach equilibrium across the two connected bodies. Hence if I walk around in rubber shoes in summer, then touch my car I will get a "zap" due to charge movement even though the car sits on rubber tires and there is no direct ground path. Think about connecting two capacitors together - same thing.

As John says - in reality perfect insulation rarely exists and so this ESD which builds up on us through movement usually flows via a short sharp pulse towards "earth" if it can find a route or it leaks to the environment more slowly; this is just like the principle behind corona discharges from high voltage generators like Tesla coils where the charge jumps into the air by ionising it (causing a purple glow) and then redistributes among air molecules on the way to ground.

The damage ESD causes to semiconductors by the way is often related to the super fast pulses of a discharge....a really fast rise time in just a few nS from zero to several kV, followed by a slower exponential shaped tail off back to 0V. This short pulse generates RF waves up to GHz range which propagate randomly around and the metal layers of modern IC's as well as the traces on a PCB can all become antennas receiving it and creating induced currents - so chaos especially for digital circuitry can abound. For analog chips unlucky enough to lie in the path of a pulse current, short but massive heating events can happen and/or electrostatic voltage overstressing for semiconductor junctions....end result = BANG.

It's a fun topic, but engineers hate it when otherwise excellent product designs can be derailed - it's not getting easier as we shrink our semiconductor devices ever smaller. It can be very hard to recreate particular failure events also.

 

[Azathoth]

I seem to have channel imbalance issues (center skewed to the right) with my L30/E30 stack, I think its the L30 because the red RCA in is a bit bent. Could this be it? I tried the DAC alone with another amp, and it was fine.

 

[JohnYang1997]

I seem to have channel imbalance issues (center skewed to the right) with my L30/E30 stack, I think its the L30 because the red RCA in is a bit bent. Could this be it? I tried the DAC alone with another amp, and it was fine.

I don't think bent RCA jack could cause it. But if you have channel imbalance issue that affecting your use in low gain, just ask the seller for a replacement.

 

[LexSombra]

Hey everyone!
I've been reading the thread regarding the ESD problems with the L30.
It seems like it was fixed, right?
I just wanted to be sure that the current L30/E30 combos on Shenzenaudio will be fixed.
Any batch number I should look for?

Thanks in advance!

 

[JohnYang1997]

Hey everyone!
I've been reading the thread regarding the ESD problems with the L30.
It seems like it was fixed, right?
I just wanted to be sure that the current L30/E30 combos on Shenzenaudio will be fixed.
Any batch number I should look for?

Thanks in advance!

All unit currently sold are fixed. You want 2012+ eg 2101, 2102 etc.

 

[LexSombra]

All unit currently sold are fixed. You want 2012+ eg 2101, 2102 etc.

Thanks @JohnYang1997!
I just ordered it.
I think my HD 600 will be glad to have this combo instead of the integrated laptop audio.

 

[peniku8]

@JohnYang1997 Is there anything like a L30 balanced planned?
Would love to see a compact headphone amplifier in that price range for my D10b

 

[Roland68]

@JohnYang1997 Is there anything like a L30 balanced planned?
Would love to see a compact headphone amplifier in that price range for my D10b

Isn't the L30 already a simplified SE headphone amplifier with the same NFCA modules as in the A90?

 

[peniku8]

Isn't the L30 already a simplified SE headphone amplifier with the same NFCA modules as in the A90?

Well I'm kinda hoping there would be an L30B model like 30$ more expensive than the L30. A 500$ headphone amp like the A90 is not in my price range.

 

[half_dog]

Buy two L30 and feed each one with a balanced signal from a DAC which has pre mode (preferably) following this: positive to left side and negative to right side, ground to ground. Then modify each side of the headphone cable with a TRS 6.35mm connector following this pinout: tip = positive, ring = negative and sleeve = not connected. Put both amp potentiometers at maximum and control the volume via DAC or software

 

[Bleib]

I seem to have channel imbalance issues (center skewed to the right) with my L30/E30 stack, I think its the L30 because the red RCA in is a bit bent. Could this be it? I tried the DAC alone with another amp, and it was fine.

Shouldn't this be easy to try by switching left and right RCA?

 

[selthier]

hi.. im new here... and have some question..

so i can get both L30+E30 with some discount coupon at more or less $170 ... its a new batch version, but i heard they still didnt put the dc protection thing in newer L30 (forgot the name) , so is it still safe to buy? ... fyi schiit & jds is much more expensive because of higher shipping rate

well , the other option is tempotec serenade idsd at $100, looks great on paper but not sure in real life

i plan to pair it with iem & headphone + speaker as pre amp .... does the standby mode work well? is it safe to always turn it on? because i will use it at my home office, and i stay there 8-10 hour a day

 

[somebodyelse]

its a new batch version, but i heard they still didnt put the dc protection thing in newer L30 (forgot the name) , so is it still safe to buy?

I don't know where you heard that. DC protection was fixed in the batch with serial numbers starting 2012, so all units currently on sale should be safe.
https://www.audiosciencereview.com/...-headphone-amplifier-review.15226/post-821877
https://www.audiosciencereview.com/...-headphone-amplifier-review.15226/post-882068