Topping DX7 Pro DAC and Headphone Amp Reviewed

[Veri]

I was actually using Bluetooth (gasp!). I usually use the USB connected to Raspberry Pi, but my wife was using Spotify, so I couldn't make use of SpotifyConnect running on Raspberry Pi.

I see, could you check if the noise is there on both bluetooth and USB? If the 4.4mm balanced is noisy with all inputs, that would indicate there's something wrong with it :/

 

[GentleEars]

I see, could you check if the noise is there on both bluetooth and USB? If the 4.4mm balanced is noisy with all inputs, that would indicate there's something wrong with it :/

Thank you for suggesting that. I switched to USB, the noise seemed to disappear from the 4.4mm balanced output. And I began to appreciate the difference between the balanced playback and the unbalanced playback.

The big discovery came next. While I switched a few more times between USB and Bluetooth sources, I noticed some of the same noise creep in even when I'm listening on USB. This made me realize, that Bluetooth signal may be the cause of the noise. Sure enough, when I turn-off Bluetooth on my phone (which was no longer needed as I was listening via USB), it improved the noise to the level where I could no longer hear it. So the source of the noise is definitely interference from Bluetooth. I am very surprised the 4.4mm balanced output is so susceptible to the low-power waves of Bluetooth.

MDR-1AM2 has a very low impedance of 16 ohms. DX7 Pro has a relatively high impedance, although I'm not sure what the value is on the 4.4mm balanced output. Do these numbers make the headphones more susceptible to this kind of noise than say 30 or 60 ohm headphones?

 

[Veri]

MDR-1AM2 has a very low impedance of 16 ohms. DX7 Pro has a relatively high impedance, although I'm not sure what the value is on the 4.4mm balanced output. Do these numbers make the headphones more susceptible to this kind of noise than say 30 or 60 ohm headphones?

Your low-impedance headphones are more susceptible to showcase this noise, yes; however I don't really understand why 3.5mm doesn't show the same problem. I suppose the bluetooth is somehow polluting the 4.4mm output!

 

[GentleEars]

Now I'm curious if other owners experience the same problem. Or there is something wrong with the 4.4mm balanced output on my particular sample of DX7 Pro...

 

[GentleEars]

Is it the cable that pickup interference from Bluetooth? Or the internals of DX7 Pro? If I get a fancy braided balanced cable, can I avoid the interference? I am curious, because I'm sure there's lots of Bluetooth waves in my crowded condominium, aside from my own Bluetooth devices.

 

[GentleEars]

Is it the cable that pickup interference from Bluetooth? Or the internals of DX7 Pro? If I get a fancy braided balanced cable, can I avoid the interference? I am curious, because I'm sure there's lots of Bluetooth waves in my crowded condominium, aside from my own Bluetooth devices.

I think it's not the cable. Here's what I did:

I switched DX7 Pro's input to USB, played music from Raspberry Pi over USB, listening with MDR-1AM2 connected to DX7 Pro's 4.4mm balanced headphone out. Within a few inches to this, I turned on Bluetooth on my smartphone, and connected to DX7 Pro. As soon as I did this, I start hearing noise in MDR-1AM2. The noise amplifies when I play music on my smartphone.

Second, on the smartphone, I disconnect Bluetooth connection to DX7 Pro, and connect to another SONY Bluetooth headphone (WH-1000XM2). I place the smartphone and WH-1000XM2, right close to both the 4.4mm balanced cable and DX7 Pro's Bluetooth antenna, and I don't hear any noise. I even moved WH-1000XM2 to a far corner of my house to see if Bluetooth transmission power gets stronger and I can detect interference on the 4.4mm cable. I can't hear any difference, and hear no noise.

This leads me to suspect, the interference on 4.4mm balanced headphone out comes from the Bluetooth circuitry on DX7 Pro itself.

 

[Veri]

Is it the cable that pickup interference from Bluetooth? Or the internals of DX7 Pro?

Internals, looks like :/ hardware issue.

 

[mundee]

Three more days before i can finally own this, I’m looking forward to it. Anyhow not sure if this has been asked, but is it possible to connect to both balanced 4.4 and unbalanced 6.3 at the same time? Also, if i connect my L30 via RCA out, can i still use the headphone outs of the dx7 pro? TIA

 

[Veri]

Anyhow not sure if this has been asked, but is it possible to connect to both balanced 4.4 and unbalanced 6.3 at the same time?

For easy loads this will work, but don't drive both a planar like Verum/other current-suckers together with another headphone or you'll run into trouble. Two efficient headphones at the same time will work.

Also, if i connect my L30 via RCA out, can i still use the headphone outs of the dx7 pro? TIA

Yes, absolutely.

 

[SRKRAM]

As my DX7 pro had an issue with the volume control I contacted Topping support for help. It's still under warranty but instead of sending it back to China for repair I asked if they would be able to send me a replacement part so I could replace it myself. They took a little persuading but they sent me the part and it arrived today.

I just performed the replacement and now I have a volume control which works perfectly.

 

[renoxd]

Why so many say that topping Dx7 pro has weak preamp section? Of course no one says why.
I don't understand that. Is there any reason for this?

 

[SRKRAM]

Why so many say that topping Dx7 pro has weak preamp section? Of course no one says why.
I don't understand that. Is there any reason for this?

I haven't heard anybody criticising the DX7 Pro's preamp, possibly because it isn't a preamp.

 

[renoxd]

DX7 Pro isn't preamp but can act as a preamp when changing volume is possible. I have heard that using Topping in this mode is not recommended.

 

[ELberto]

I was scratching my head... Probably referring to the hp amp.

 

[renoxd]

 

[peanuts]

they can design a reasonable product, yet cant find anyone who knows english

 

[ELberto]

Translation aside, I'm not sure what they're referring to. I'm not experiencing any weirdness using both the balanced and unbalanced outputs (simultaneously) to feed 2 pairs of powered speakers.

 

[BDWoody]

Why so many say that topping Dx7 pro has weak preamp section? Of course no one says why.
I don't understand that. Is there any reason for this?

No idea. Not even sure what that means.

It can certainly act as a preamp in the sense of volume control. No issues with that.

 

[GentleEars]

I use DX7 Pro as a pre-amp, connected to a power-amp, AUDIOPHONICS MPA-S250NC XLR Class D Stereo Amplifier via a pair of XLR cables. It works great. On the other hand, I'm not an experienced audiophile, and don't have another quality amplifier with pre-amp output to compare. In my mind, it makes a very simple set-up with minimal room for signal degradation.

 

[renoxd]

Is it possible that DAC mode has better dynamics or overall sound quality than Pre mode?

"At this mode, in order to achieve the best performance and cooperate with other devices in the system, headphone amp will be turn off and the volume will be uncontrollable"

Why they are connecting volume controlling with performance? Or maybe my English is not good enough and I understand this in a bad way.
They are some opinions, not only about DX7 Pro regarding pre amp, that digital control volume need to be very good made to not affect sound.