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Topping L30 Headphone Amplifier Review

tvih

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Man, I just really wish I could try out this thing without buying to see if it'd be worthwhile. I mean I don't at all doubt that it's good, I just doubt if my ears are good enough to appreciate the difference to my current setup. Drooling at the EX5 too as per my post on that thread but I think in the end the DAC side of that raises the overall cost too much compared to the L30, given my finances and not-very-critical listening - even with my current DAC being around a decade old and cheap (HotAudio DAC Destroyer - corny names for the win; based on the PCM2705 chip), I never noticed any problems with it. Though being able to test that too alongside the L30 would be even better, of course.
 

Blaze_NY

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Just picked this unit up and wow it drives my hd600's nicely i tend to listen to my music at really high volumes and this unit definitely does that. To my ears it sounds better than my previous amp the jds atom
 

Jave

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I went through a lot of the thread, but didn't see whether Topping checked how the different ESD\DC fixes affected the audio performance of the device?
 

solderdude

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Grounding the enclosure using a pogo-pin (that's all that has been done) is not affecting/changing performance.
There was a DC protection change as well but this is not in the audio path so again no influence.
 

SaberCat

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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.
 
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fun

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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 bolt 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.
That's nice. May I ask where did you get the power supply for the 2nd unit?
 

SaberCat

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I had a spare wall wart with 15V 1.5A AC output and with a power plug which fits the L30 very nicely (luckily, though it would not be hard to solder a new one on had it not fitted - the AC input socket is a common one).

I suspect anything in the range 12-16V AC, 1A or higher will likely work fine....anything much higher in voltage will risk overheating of the internal regs. You can find them if you ask around the electronics parts stores......be careful though - mostly what is sold online are DC adapters which might appear to work (I haven't tried it) but I would not use them as it's not what the unit was designed for and even if it did work, it may cause the internal bridge rectifier to overheat as two of the diodes won't be seeing any use.
 

JohnYang1997

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I had a spare wall wart with 15V 1.5A AC output and with a power plug which fits the L30 very nicely (luckily, though it would not be hard to solder a new one on had it not fitted - the AC input socket is a common one).

I suspect anything in the range 12-16V AC, 1A or higher will likely work fine....anything much higher in voltage will risk overheating of the internal regs. You can find them if you ask around the electronics parts stores......be careful though - mostly what is sold online are DC adapters which might appear to work (I haven't tried it) but I would not use them as it's not what the unit was designed for and even if it did work, it may cause the internal bridge rectifier to overheat as two of the diodes won't be seeing any use.
DC adapters will not work. And any 3rd party AC adapters will not have guaranteed performance. They can work ok. But that's all.
It's required to asked to destroy the "faulty" unit before the replacement sent out. If you really don't want to, then good for you. But it's not endorsed.
 

Roland68

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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.
But you already know that you can still blow up your HD650?
If the device connected via chinch also has no earthed ground ...?
And the old DC protection circuit was also modified in the new devices, maybe there is a reason?

There is more than one reason why topping demands that the old equipment be destroyed.
 

SaberCat

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DC adapters will not work. And any 3rd party AC adapters will not have guaranteed performance. They can work ok. But that's all.
It's required to asked to destroy the "faulty" unit before the replacement sent out. If you really don't want to, then good for you. But it's not endorsed.
That's cool and you are quite right John - however I can confirm that the seller absolutely did not ask me to destroy the old unit, and as long as I do not resell it (I won't) then I'm not harming anyone by modding and recommissioning it. Also the AC adapter I am using is just a transformer in a plug pack - as with the original PSU. Of course it might not be as nice from an audio perspective, but it's a heavy chunky unit rated 1.5A @15V, I cannot hear any difference and am not about to put it onto an audio analyzer.
 

JohnYang1997

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That's cool and you are quite right John - however I can confirm that the seller absolutely did not ask me to destroy the old unit, and as long as I do not resell it (I won't) then I'm not harming anyone by modding and recommissioning it. Also the AC adapter I am using is just a transformer in a plug pack - as with the original PSU. Of course it might not be as nice from an audio perspective, but it's a heavy chunky unit rated 1.5A @15V, I cannot hear any difference and am not about to put it onto an audio analyzer.
That's ok.
 

SaberCat

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But you already know that you can still blow up your HD650?
If the device connected via chinch also has no earthed ground ...?
And the old DC protection circuit was also modified in the new devices, maybe there is a reason?

There is more than one reason why topping demands that the old equipment be destroyed.

It's OK dude - I do appreciate the advice, which is of course well meant. FYI I am an EE who has worked for a big US semi manufacturer and have a reasonably good understanding of ESD risks and mitigations in semiconductor electronics, and so feel comfortable with the solution I have implemented for myself. 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). Of course I cannot implement any PCB layout or component changes Topping may have added to further improve ESD safety but I can still reduce the key risk factor which is a charge jumping from me, to the vol pot and thence onto the PCB.

Connecting the chassis to the ground plane (as Topping has done with their pogo pin), and also doing the most to ensure an electrical connection of the front panel control shafts to this grounded chassis provides a much easier route for ESD discharges to dissipate safely than by flowing through the semiconductor devices on the PCB causing chaos. We are talking about many KV but very tiny currents in these discharges, and they can behave in really strange ways so this is not always simple to predict. Anyway you cannot eliminate ESD risk entirely whatever you do - it's a probability game.
 

JohnYang1997

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It's OK dude - I do appreciate the advice, which is of course well meant. FYI I am an EE who has worked for a big US semi manufacturer and have a reasonably good understanding of ESD risks and mitigations in semiconductor electronics, and so feel comfortable with the solution I have implemented for myself. 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). Of course I cannot implement any PCB layout or component changes Topping may have added to further improve ESD safety but I can still reduce the key risk factor which is a charge jumping from me, to the vol pot and thence onto the PCB.

Connecting the chassis to the ground plane (as Topping has done with their pogo pin), and also doing the most to ensure an electrical connection of the front panel control shafts to this grounded chassis provides a much easier route for ESD discharges to dissipate safely than by flowing through the semiconductor devices on the PCB causing chaos. We are talking about many KV but very tiny currents in these discharges, and they can behave in really strange ways so this is not always simple to predict. Anyway you cannot eliminate ESD risk entirely whatever you do - it's a probability game.
The other protection he mentioned is revised output DC protection.
 

JohnYang1997

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So overvoltage protection on the rails after the LDO regs in case of LDO failure due to ESD or other factor ?
Amplifier output at headphone terminal. So that it will open the relay to protect headphones if the amplifier failed.
 

SaberCat

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Amplifier output at headphone terminal. So that it will open the relay to protect headphones if the amplifier failed.
That's a good additional safety measure for sure John; was there no DC protection at all on the output in the earlier design ?

I'll not sweat about it since my HD650's are ancient anyway....and I reckon I've reduced the major risk of DC getting to the output through the TPA6120a's detonating due to ESD. If they fail for any other reason, well that's bad luck but pretty unlikely to happen.....famous last words I know !
 

JohnYang1997

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That's a good additional safety measure for sure John; was there no DC protection at all on the output in the earlier design ?

I'll not sweat about it since my HD650's are ancient anyway....and I reckon I've reduced the major risk of DC getting to the output through the TPA6120a's detonating due to ESD. If they fail for any other reason, well that's bad luck but pretty unlikely to happen.....famous last words I know !
There was a circuit but due some oversight in the design process, the protection circuit didn't work as intended. Related to protection opamp stability and input protection diodes as well as the threshold. It was a bit complex issue. The chance of getting the disastrous result similar to that caused by ESD is minimal.
 
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