Topping L30 Headphone Amplifier Review

[Doodski]

Any thump, pop or crack at startup, shutdown, or loss of power?

Yes, and how about some pics of the PCB and layout.

 

[JohnYang1997]

Wow, nice!

Can it handle 16 ohm load? How much power at 16 Ohm?

Any thump, pop or crack at startup, shutdown, or loss of power?

3.5W 16ohm dual channel driven.
No pop on startup and shutdown.
The indicator LED is gentle and warm white color that's visible at all angles.

 

[wwenze]

I remember people criticized nwavguy's design for using half-wave rectification saying it creates more ripple

Well... what ripple?

 

[JohnYang1997]

I remember people criticized nwavguy's design for using half-wave rectification saying it creates more ripple

Well... what ripple?

Simply.

 

[Bamboszek]

Chapeau bas! Stunning performance in affordable package.
I had somewhat similar idea with my composite headphone amplifier. TPA6120A2 nested inside feedback loop and half wave PSU.
I wish I could own APx555B and be able to optimize my amplifier to such high SINAD levels.
Do you also observed increased distortion from thermal feedback effect at TPA6120A2? It happens with heavy loads like 16-50Ω at low frequencies.
johnc from Texas Instruments introduced me to this distortion mechanism here.
Is L30 DC-coupled? I see some relays, only power-on delay or maybe there is DC protection too?

 

[urfaust]

That looks more inline with what we got

 

[JohnYang1997]

Chapeau bas! Stunning performance in affordable package.
I had somewhat similar idea with my composite headphone amplifier. TPA6120A2 nested inside feedback loop and half wave PSU.
I wish I could own APx555B and be able to optimize my amplifier to such high SINAD levels.
Do you also observed increased distortion from thermal feedback effect at TPA6120A2? It happens with heavy loads like 16-50Ω at low frequencies.
johnc from Texas Instruments introduced me to this distortion mechanism here.
Is L30 DC-coupled? I see some relays, only power-on delay or maybe there is DC protection too?

L30 doesn't show that behaviour.
AC coupled using a large electrolytic cap. Has DC protection implemented. Low frequency distortion is still under 0.00003% (4 zeros after decimal point).

 

[boXem]

Thanks for the review @amirm!
Did you have time to look at the input impedance?

 

[Veri]

Low frequency distortion is still under 0.00003% (4 zeros after decimal point).

. Congrats John, this is one great amp

 

[JohnYang1997]

Thanks for the review @amirm!
Did you have time to look at the input impedance?

2.5k for mid and high gain setting. 7.5k for low gain setting.

 

[amirm]

9V for mid gain, 3V for high gain. Internal works at 15V.

Oh I was asking about input voltage.

 

[boXem]

2.5k for mid and high gain setting. 7.5k for low gain setting.

That's very low. Why?

 

[JohnYang1997]

Oh I was asking about input voltage.

Yes, those are input voltages required for max power outputs. 9V for mid gain, 3V for high gain.

 

[JohnYang1997]

That's very low. Why?

Rejection to interference. And I directly use pot at the input. Pot value has to be small in order to get low noise at all volume position (50% position).

 

[Bamboszek]

To keep thermal noise down.
Thermal nosie of 10kΩ resistor in 20°C with 20kHz BW is already 1.8µV.
IMHO any DAC with comparable performance to this amplifier would drive 2k5 without any problems. If we want compatibility with worse gear 10k or more would be preferable.
EDIT
John was a bit faster

 

[tecnogadget]

OUTSTANDING !! I can’t believe one can get such reference performance at $130. It feels like yesterday when you needed to spend 4 figures and no objetive data...

 

[Doodski]

OUTSTANDING !! I can’t believe one can get such reference performance at $130. It feels like yesterday when you needed to spend 4 figures and no objetive data...

Even today one could spend 4 figures to meet it or beat it!

 

[boXem]

To keep thermal noise down.
Thermal nosie of 10kΩ resistor in 20°C with 20kHz BW is already 1.8µV.
IMHO any DAC with comparable performance to this amplifier would drive 2k5 without any problems. If we want compatibility with worse gear 10k or more would be preferable.
EDIT
John was a bit faster

Thermal noise depends the way the input is implemented. You can have high impedance low noise input.
I would be curious to see M400 RCA -> L30 bode plot...
More generally, I don't think that consumers should pay attention to such details. An input stage should work well with whatever it's fed (the same for a line output BTW). Else the door is open to BS like "synergies" between gear.

 

[JohnYang1997]

Thermal noise depends the way the input is implemented. You can have high impedance low noise input.
I would be curious to see M400 RCA -> L30 bode plot...
More generally, I don't think that consumers should pay attention to such details. An input stage should work well with whatever it's fed (the same for a line output BTW). Else the door is open to whatever BS like "synergies" between gear.

M400 RCA output supposedly have buffer but they fked up the LPF. It pairs with E30 and D10s so no issue from my point of view. 2.5K is low in your book. But higher than 600ohm means high to me.

 

[pos]

3.5W 16ohm dual channel driven.
No pop on startup and shutdown.
The indicator LED is gentle and warm white color that's visible at all angles.

Nice!
What about 8 ohms then?