Topping DX7 Pro DAC and Headphone Amp Reviewed

[NielsMayer]

By the pictures, there is NO WM8804/8805 on optical circuit.

WM8804 SSOP has 20 pin.
WM8805 SSOP has 28 pin.

The only thing I saw was that HEX inverter.

"IMHO pics from a different model are irrelevant and show no similarities... "

There are a lot sections pretty close (>90%) to the DX7 Pro.

Ooops. nevermind.. apparently i was confused. Yes these are 20 and 28 pin chips.

 

[Alou]

Here is the official answer from TOPPING on headphones :

Thank you for contacting TOPPING support. We are happy to assist.

Actually DX7Pro is able to drive 600ohm headphones, the specifications we write are conservative. The headphone is not driven by LME49720, but by the more powerful AD8397.

Best Regards,
--------------------

TOPPING SERVICE

 

[NielsMayer]

Here is the official answer from TOPPING on headphones :

Thank you for contacting TOPPING support. We are happy to assist.

Actually DX7Pro is able to drive 600ohm headphones, the specifications we write are conservative. The headphone is not driven by LME49720, but by the more powerful AD8397.

Best Regards,
--------------------

TOPPING SERVICE

So would this mean that the Lme49720 just inverts the input to AD8397 ? If so couldn't the Lme49720 socket be jumpered to eliminate one op amp if one cares not about inversion? Assuming previous circuit doesn't need buffering to AD8397.

 

[Alou]

I cant really say unless i have a circuit diagram ,but thats what they replied.

 

[MediumRare]

So would this mean that the Lme49720 just inverts the input to AD8397 ? If so couldn't the Lme49720 socket be jumpered to eliminate one op amp if one cares not about inversion? Assuming previous circuit doesn't need buffering to AD8397.

Why would you mess with something performing so well already?

 

[Alou]

I agree ,in my days as an engineer i found out that its better to built something from scratch to your tastes then spends 1000 of hours to modify something with unknown results.
Besides what the point if something is allready good.

 

[Bjoran]

Here is the official answer from TOPPING on headphones :

Thank you for contacting TOPPING support. We are happy to assist.

Actually DX7Pro is able to drive 600ohm headphones, the specifications we write are conservative. The headphone is not driven by LME49720, but by the more powerful AD8397.

Best Regards,
--------------------

TOPPING SERVICE

Ok, then I have a theory.
I might be totally wrong but maybe one half of the LME49720 is inverted to create a differential stage, feeding the dual AD8397 with a signal for the balanced headphone output, for each channel.

 

[Gradius]

AD8397 is a Rail-to-Rail, High Output Current Amplifier:
The AD8397 comprises two voltage feedback operational amplifiers capable of driving heavy loads with excellent linearity. The common-emitter, rail-to-rail output stage surpasses the output voltage capability of typical emitter-follower output stages and can swing to within 0.5 V of either rail while driving a 25 Ω load. The low distortion, high output current, and wide output dynamic range make the AD8397 ideal for applications that require a large signal swing into a heavy load. Fabricated with Analog Devices, Inc., high speed extra fast complementary bipolar high voltage (XFCB-HV) process, the high bandwidth and fast slew rate of the AD8397 keep distortion to a minimum.


While LME49720 is a High Fidelity Audio Operational Amplifier (Dual High Performance):
The LME49720 device is part of the ultra-low distortion, low noise, high slew rate operational amplifier series optimized and fully specified for high performance, high fidelity applications. Combining advanced leading-edge process technology with state-of-the-art circuit design, the LME49720 audio operational amplifiers deliver superior audio signal amplification for outstanding audio performance. The LME49720 combines extremely low voltage noise density (2.7nV/√Hz) with vanishingly low THD+N (0.00003%) to easily satisfy the most demanding audio applications.

So AD8397 is an all around purpose amp, while LME49720 is more of a headphone amp.

 

[Gradius]

Ok, then I have a theory.
I might be totally wrong but maybe one half of the LME49720 is inverted to create a differential stage, feeding the dual AD8397 with a signal for the balanced headphone output, for each channel.

It really could be. A diagram would be nice thought.

 

[harleyguy07]

*NO* otherwise how do you expect to change the OPAMPs in case you want in first place ?

That is what I thought about when i took the resistor out of mine. They build these things with op amp rolling in mind and to do that you have to take the front panel off, disconnect the ribbon cable and pull the circuit board out of the back. If they know that people are going to roll then I would not think it would void anything

 

[harleyguy07]

I have read on other forums people talking about Sabre dac chips being fatiguing after a while. I have been listening to this dac for hours now and I will say that it holds it own with some damn expensive upper level dac's I've heard over the years. And would say that it at least stands up to the best I have heard at any price. It has nothing to be ashamed of that's for sure. But I have not had one moment of fatigue out of this thing the whole time. I know people talk about AKM chips in the Topping dacs being warmer and the Sabres having more detail but to me this dac has killer detail while not being fatiguing. Maybe its just me

 

[Bjoran]

Here is the official answer from TOPPING on headphones :

Thank you for contacting TOPPING support. We are happy to assist.

Actually DX7Pro is able to drive 600ohm headphones, the specifications we write are conservative. The headphone is not driven by LME49720, but by the more powerful AD8397.

Best Regards,
--------------------

TOPPING SERVICE

I am a bit confused about their answer that the headphone is not driven by LME49720, because in their own product information they say that it is (except the typo 47920):
http://www.tpdz.net/products_detail/productId=44.html
I still think there is a combination of the LME49720 and the AD8397.

 

[Bjoran]

I have read on other forums people talking about Sabre dac chips being fatiguing after a while. I have been listening to this dac for hours now and I will say that it holds it own with some damn expensive upper level dac's I've heard over the years. And would say that it at least stands up to the best I have heard at any price. It has nothing to be ashamed of that's for sure. But I have not had one moment of fatigue out of this thing the whole time. I know people talk about AKM chips in the Topping dacs being warmer and the Sabres having more detail but to me this dac has killer detail while not being fatiguing. Maybe its just me

No, it is not just you. You can count me in, I totally agree with you about the good sound of the DX7 Pro. The choice of DAC chip is only one of several parts. One of the most important parts is the analogue stage after the DAC and here has Topping really succeeded.

 

[evrial]

Not sure this was mentioned anywhere, does it auto turn on/off like dx3 pro?

 

[Category 5]

I am a bit confused about their answer that the headphone is not driven by LME49720, because in their own product information they say that it is (except the typo 47920):
http://www.tpdz.net/products_detail/productId=44.html
I still think there is a combination of the LME49720 and the AD8397.

They may be using Ad8397 as a current amp in combination with lm49720 as a voltage amp. I’ve seen this configuration in another headphone amp at some point, but can’t for the life of me remember where. It was 8397 and another op-amp though.

I agree about the performance of this DAC. It sounds great, and I do not subscribe to the “all DACs sound the same” camp. I do think ESS has a sound, and it’s working well for me in this new DAC.

 

[MediumRare]

Not sure this was mentioned anywhere, does it auto turn on/off like dx3 pro?

Yes.

 

[NielsMayer]

Is there a cheaper or better device to plugin to the IIS-LVDS (HDMI) input on the DX7 Pro, than say
https://shenzhenaudio.com/products/matrix-x-spdif-2-32bit-768khz-dsd512-hifi-audio-usb-interface ??
To get the same or similar levels of USB performance (low jitter, so nothing to "dejitter") as you'd get with the internal USB interface.
(no, i don't want a USB switcher, i want three "live" USB inputs switchable by remote, the other is a NVIDIA Shield->ToppingD10->SPDIF).

The main issue I see with all the cheap USB->IIS converters ( https://www.amazon.com/gp/product/B07R8138XL/ ) is they output single-ended IIS, not IIS-LVDS (low voltage differential signalling as needed by DX7Pro). I was happy to wire up an HDMI port myself ( https://www.amazon.com/gp/product/B07FYGPFR5/ ) but adding an LVDS chip and expecting the entire potschky job to perform in any decent way is wishful thinking. Bad enough if the wires are not short in length or improperly paired and twisted before crossing another radiating wire, in a hand-built IIS-LVDS cable.

 

[dmac6419]

Not sure this was mentioned anywhere, does it auto turn on/off like dx3 pro?

YUP

 

[Bjoran]

Is there a cheaper or better device to plugin to the IIS-LVDS (HDMI) input on the DX7 Pro, than say
https://shenzhenaudio.com/products/matrix-x-spdif-2-32bit-768khz-dsd512-hifi-audio-usb-interface ??
To get the same or similar levels of USB performance (low jitter, so nothing to "dejitter") as you'd get with the internal USB interface.
(no, i don't want a USB switcher, i want three "live" USB inputs switchable by remote, the other is a NVIDIA Shield->ToppingD10->SPDIF).

The main issue I see with all the cheap USB->IIS converters ( https://www.amazon.com/gp/product/B07R8138XL/ ) is they output single-ended IIS, not IIS-LVDS (low voltage differential signalling as needed by DX7Pro). I was happy to wire up an HDMI port myself ( https://www.amazon.com/gp/product/B07FYGPFR5/ ) but adding an LVDS chip and expecting the entire potschky job to perform in any decent way is wishful thinking. Bad enough if the wires are not short in length or improperly paired and twisted before crossing another radiating wire, in a hand-built IIS-LVDS cable.

Why not this one:
https://shenzhenaudio.com/collectio...k-dsd512-dop-and-native-dsd-digital-interface
Only one USB-input but it has differential I2S signal with LVDS output level.

 

[Veri]

Why not this one:
https://shenzhenaudio.com/collectio...k-dsd512-dop-and-native-dsd-digital-interface
Only one USB-input but it has differential I2S signal with LVDS output level.

Read many reports of this one being rather buggy