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Topping L30 Headphone Amplifier Review

artburda

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Here we go:

L30.jpgL30-2.jpg

Looks alright to me.
 

solderdude

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Parts can fail without it showing on the outside.
My hunch is the OPA is at fault.

Did you find what was rattling inside ?
I read somewhere it may have been metal coming from one of the rear screws.

When you have a multimeter I am interested in the following thing:
Is the volknob made of metal ?
Does the volpot shaft make electrical contact with the RCA shield ?
 

Dotcha

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Parts can fail without it showing on the outside.
My hunch is the OPA is at fault.

Did you find what was rattling inside ?
I read somewhere it may have been metal coming from one of the rear screws.

When you have a multimeter I am interested in the following thing:
Is the volknob made of metal ?
Does the volpot shaft make electrical contact with the RCA shield ?
On my L30 (not broken), volpot shaft and RCA shield is electrically disconnected.
 

solderdude

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Yes, looked like it.
The bodies of the switches are soldered onto the board.
Are those bodies electrically connected to the ground (RCA shield) ?

The next question is whether or not the volknob is made of metal.
 

Dotcha

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Yes, looked like it.

The next question is whether or not the volknob is made of metal.
1610453895810.png

on my L30 (not broken), knob seems to be partly metallic, but its surface is coated so it's not conductive.
The attachment at the center grabs the D shaft and insulates it at the same time.
 

artburda

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Location
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Parts can fail without it showing on the outside.
My hunch is the OPA is at fault.

Did you find what was rattling inside ?
I read somewhere it may have been metal coming from one of the rear screws.

When you have a multimeter I am interested in the following thing:
Is the volknob made of metal ?
Does the volpot shaft make electrical contact with the RCA shield ?
The rattling comes from the earbud not the L30. After doing the ESD tests and when I played music again with the earbuds attached to the L30, the right earbud got really hot. Later on I noticed that somehow a part inside the earbud must have gotten loose, because it rattles when you shake it.
 

solderdude

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View attachment 105564
on my L30 (not broken), knob seems to be partly metallic, but its surface is coated so it's not conductive.
The attachment at the center grabs the D shaft and insulates it at the same time.

A 20kV ESD jolt can easily spark from the metal around the plastic to the shaft.

If I owned an L30 and it still works I would put some wire around the metal screw part around the shaft and connect the other end of the wire to the groundplane.
When the switches also are not grounded I would ground these to the groundplane as well.

Chances are the ESD problems may possibly be solved this way.
Of course the not (properly ?) functioning DC protection is not solved this way.
 

ragecandy

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Man this is so sad, finally a decent stack that I could buy without spending more on shipping and taxes than the actual thing, I’m #2007 batch so just keeping it seems like a no-go, got it in september in aliexpress so the only chance is for topping to come in and make it right now.
Shipping it back to china is gonna cost like $60 btw...:facepalm:
 

solderdude

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That trace appears to go to the dc detection circuit. So if its blowing that might explain why the amp isnt shutting down when the output shorts.

They are the power supply lines to the OPA.
 
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