Topping L50 Review (Headphone Amp)

[JohnYang1997]

As always, input impedance is missing. They show only "nice" numbers.

2.5k for SE, 2k for Bal. Thank you very much.

 

[pma]

2.5k for SE, 2k for Bal. Thank you very much.

Thank you.

 

[Labjr]

Back to an AC transformer.

 

[Matias]

Would be interesting to see how the stack measures, that is, dashboard FFT, multitone, THD+N x frequency etc of the E50+L50 together. Will they remain the same?

 

[audio_tony]

2.5k for SE, 2k for Bal. Thank you very much.

And once again, way too low, 10k being an absolute realistic minimum, and even better 22k / 47k

It's already been proven in this very forum that very a low input impedance is not required for good SINAD figures.

 

[JohnYang1997]

And once again, way too low, 10k being an absolute realistic minimum, and even better 22k / 47k

It's already been proven in this very forum that very a low input impedance is not required for good SINAD figures.

Yeah. It's also proven that "low" input impedance is not to achieve high SINAD figures.

 

[audio_tony]

Yeah. It's also proven that "low" input impedance is not to achieve high SINAD figures.

So why such a low input impedance then?

Genuine question.

 

[JohnYang1997]

So why such a low input impedance then?

Genuine question.

If I add input buffer for each input I would need 3 extra high performance opamps. Where I only have one now in the device. Or I have to increase the pot resistance which will affect noise performance after attenuation. At -6dB attenuation point 2.5k pot will have 625ohm equivalent noise resistance. I wouldn't accept higher than that.
2k - 2.5k is not really low impedance in the sense of actual engineering. Opamps can drive 600ohm even 300ohm for decades. At level of 2-2.5V is even less of an issue.
There are also components of noises that are low energy current sources. High input resistance will let these noises into the system. Often people use 1kohm to cure this, 2-2.5k ohm is a good compromise point.
This is also ridiculous since people are only seeing this because it's showing as an input. Internally in many DAC's output stage the equivalent input impedance would be around 1kohm or even lower in a low noise design.
The low impedance can cause issue if the output of the DAC is capacitor coupled with low capacitance value like 2.2u or 1uF. Or transformer output (may or may not). Resistive output impedance only would have a bit of attenuation which is a non issue unless the output impedance is way too high.

 

[pma]

At -6dB attenuation point 2.5k pot will have 1.25k equivalent noise resistance

No. It will be 625 ohm if driven from near to zero impedance - Thevenin theorem.

 

[JohnYang1997]

No. It will be 625 ohm if driven from near to zero impedance - Thevenin theorem.

Corrected.

 

[Lithovox]

Which Opamp does the new L50 amp use? 6120A2 like the L30 and A90, or OPA1656 like the A30Pro, or something different?

One of the L50 product images is captioned "a circuit based on the same working principle as the one in the A30 Pro" but the picture itself shows a 6120. Judging from the image I'm guessing it's a nested 6120 like the L30, but now with a power supply bootstrap for more output range like in the A30 Pro.

 

[Theriverlethe]

No measurements of the SE output?

 

[JohnYang1997]

No measurements of the SE output?

Two outputs are the same.

 

[Theriverlethe]

Two outputs are the same.

In distortion or output power?

 

[JohnYang1997]

In distortion or output power?

Everything. Two outputs are directly connected to each other.

 

[andrewskaterrr]

@amirm thank you very much for this review.

@Topping, please enter the Audio & Video Receiver /Audio & Video Processor market!! or at least the multichannel DAC market!

This is what I want so bad. I'm to the point where I wish there was some way to split apart the Post Atmos processing signal (maybe via PC?) and send it out to multiple E30s via multiple Toslink (stereo) or USB cables, then send to my amps.

 

[thin bLue]

WoW! lower gain than L30, sweeeeeet
Soooooooo seductive to IEM users

nice job, JohnYang you did it again!

 

[tential]

Price =/ performance - Topping

 

[infinitesymphony]

If the SINAD is the same, is there any practical reason to go for the L50 over the L30 other than the peace of mind of knowing your signal chain is balanced from beginning to end, i.e. is anyone really reaping the benefits of staying balanced at this stage with such short distances in home or studio environments?

 

[TheTalbotHound]

One of the L50 product images is captioned "a circuit based on the same working principle as the one in the A30 Pro" but the picture itself shows a 6120. Judging from the image I'm guessing it's a nested 6120 like the L30, but now with a power supply bootstrap for more output range like in the A30 Pro.

yeah i guess it would undercut the point of the A30pro somewhat since that is internally single ended too.