Help with Topping A30Pro Review (Balanced Headphone Amp) problems

[Alalla]

still humming

 

[rcstevensonaz]

Try the following in order and re-check noise each time:

• Unplug DX3 from wall (leaving rest of cable as it is)
• Unplug power cable from DX3 and remove the power cable from the area
• Unplug the audio cable out of DX3 (leaving rest of cable as it is)
• Unplug the audio cable from the A30Pro (leaving rest of cable as it is)
• Remove the audio cable from the area (so only A30Pro plugged in and headphones are now in the picture)

Reset back to the picture you posted above:

• Unplug audio cable from DX3 (leaving rest of cable as it is; power connected)
• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected)
• Remove audio cable from area entirely
• Unplug power cord into DX3 (leaving rest of cable as is)
• Keeping DX3 power plugged in, move the cable so that it is moved away from the DX3

Now, replace the DX3 with the L30 II and repeat both of the scenarios above.

 

[Alalla]

DX3 + A30 (high gain) = Humming

• Unplug DX3 from wall (leaving rest of cable as it is) = no humming
• Unplug power cable from DX3 and remove the power cable from the area = no humming
• Unplug the audio cable out of DX3 (leaving rest of cable as it is) = no humming
• Unplug the audio cable from the A30Pro (leaving rest of cable as it is) = no humming
• Remove the audio cable from the area (so only A30Pro plugged in and headphones are now in the picture) = no humming

Reset back to the picture you posted above:

• Unplug audio cable from DX3 (leaving rest of cable as it is; power connected) = humming / when i unplug it and leave it by the dx3 i hear humming but if i move the cable away from it the humming stops
• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no humming
• Remove audio cable from area entirely = no humming

L30II (high gain) + A30 (high gain) = Hissing

• Unplug L30 from wall (leaving rest of cable as it is) = no noise
• unplug power cable from L30 and remove the power cable from the area = no noise
• Unplug the audio cable out of L30 (leaving rest of cable as it is) = no noise
• Unplug the audio cable from the A30Pro (leaving rest of cable as it is) = no noise
• Remove the audio cable from the area (so only A30Pro plugged in and headphones are now in the picture) = no noise

Reset back to the picture you posted above:

• Unplug audio cable from L30 (leaving rest of cable as it is; power connected) = no noise
• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no noise
• Remove audio cable from area entirely = no noise

 

[rcstevensonaz]

DX3 + A30 (high gain) = Humming

• Unplug DX3 from wall (leaving rest of cable as it is) = no humming
• Unplug power cable from DX3 and remove the power cable from the area = no humming
• Unplug the audio cable out of DX3 (leaving rest of cable as it is) = no humming
• Unplug the audio cable from the A30Pro (leaving rest of cable as it is) = no humming
• Remove the audio cable from the area (so only A30Pro plugged in and headphones are now in the picture) = no humming

Reset back to the picture you posted above:

• Unplug audio cable from DX3 (leaving rest of cable as it is; power connected) = humming / when i unplug it and leave it by the dx3 i hear humming but if i move the cable away from it the humming stops
• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no humming
• Remove audio cable from area entirely = no humming

One last permutation here... Reset back to the picture you posted above:

• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = ??? / ???
• Unplug audio cable from DX3 (leaving rest of cable as it is; power connected) = no humming
• Remove audio cable from area entirely = no humming

And one other test: reset as picture shown above:

• Remove the audio cable entirely and push the DX3 and A30Pro so that they are close together (but not touching)

L30II (high gain) + A30 (high gain) = Hissing

• Unplug L30 from wall (leaving rest of cable as it is) = no noise
• unplug power cable from L30 and remove the power cable from the area = no noise
• Unplug the audio cable out of L30 (leaving rest of cable as it is) = no noise
• Unplug the audio cable from the A30Pro (leaving rest of cable as it is) = no noise
• Remove the audio cable from the area (so only A30Pro plugged in and headphones are now in the picture) = no noise

Reset back to the picture you posted above:

• Unplug audio cable from L30 (leaving rest of cable as it is; power connected) = no noise
• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no noise
• Remove audio cable from area entirely = no noise

Where is the volume control set on the A30Pro?

• Is the hissing very slight or significant?
• Do you hear the hiss at all audio volume levels or only after the volume knob is turned up higher?
• And if only when turned up higher, is the hiss present at levels on the volume knob that you normally listen or only at levels much higher?

 

[Alalla]

• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no humming
• Remove the audio cable entirely and push the DX3 and A30Pro so that they are close together (but not touching) = no humming
  
  Its about 2/3 on the dial when it starts to make noise. (high gain)
  its quite noticeable not extremely loud, more like someone whispering into your ears.
  At the volumes i listen at it just becomes noticeable.
• 

 

[rcstevensonaz]

• Unplug audio cable from A30Pro (leaving rest of cable as it is; power connected) = no humming
• Remove the audio cable entirely and push the DX3 and A30Pro so that they are close together (but not touching) = no humming
  
  Its about 2/3 on the dial when it starts to make noise. (high gain)
  its quite noticeable not extremely loud, more like someone whispering into your ears.
  At the volumes i listen at it just becomes noticeable.

Thanks. I think this will be my last of questions: do you get any hissing or other noise when it is just the A30Pro by itself and nothing else connected to it?

 

[Alalla]

Thanks. I think this will be my last of questions: do you get any hissing or other noise when it is just the A30Pro by itself and nothing else connected to it?

Nope nothing. only when i move the knob there is a slight crackling noise. but no hissing or humming just quiet.

 

[rcstevensonaz]

Nope nothing. only when i move the knob there is a slight crackling noise. but no hissing or humming just quiet.

Thanks for the extensive data and testing to isolate. I'll let others chime in if they have better insights, but here is my instincts of the issue:

A30Pro: no issue

• Rationale: when everything else is disconnected, you do not hear any noise even at the highest gain settings. So the issue of humming and hiss are not due to the baseline noise of this headphone amplifier.

DX3: defective unit that is generating abnormally high RF signals.

• Rationale: you still hear the humming even with the audio cable is disconnected from the unit DX3 unit itself (i.e., the cable is acting as an antenna, as you surmised in an earlier posting) and picking up the noise over the air).
• Note: because you moved the units away from your other electronics, there are no other sources that would be contributing to that noise*; and you have isolated the audio cable away from the power cords so that the humming noise is not being injected by the power cables.
• Note: because the humming happens even when the cable is physically disconnected from DX3 (but still in close proximity), this is not a ground loop issue or a noise-floor gain staging issue.
• Action: work with TOPPING to get a replacement fix unit or for further diagnostics on the DX3
• Potential other diagnostic step: route the DX3 to another headphone amp (e.g., DX3 -> L30II) instead of the A30Pro and follow the same testing tests and confirm that the other headphone amp likewise is picking up this humming issue under the same circumstances. If it does not, I'm at a loss since that would indicate some other interaction is at play.

L30II to A30Pro: I believe this is a gain staging issue

• Rationale: when gain staging is not set properly, noise floor from earlier components can become exaggerated and then overamplified by the final stage.
• Suggestion: read the Sweetwater article on "Gain Staging like a Pro" or other materials for how to properly set gain stages through the audio chain.
• Note: in general, you should be ideally sending through the audio signal from L30II at normative gain (0 dB) to the last component (A30Pro), and then attenuate volume downward at the last component. In your testing case, your intermediate L30II may be applying 16.5 dB on the audio signal it is sending to the A30Pro. So for this test, instead set the L30II so that it passes through the input unbalanced audio (RCA in) to the output unbalanced audio (RCA out) at 0 dB nominal gain with no increase or decrease in the audio gain. Then, at the A30Pro, play music at your range of listening volumes and notice which settings are most appropriate and where your volume dial ranges between while the music is being played. Then, mute the input music (keeping all other settings as they were), and see whether you are stilling hearing any hiss on the A30Pro within that range of the volume dial.
• Action: set gain staging appropriately... but this isn't your final audio chain, so don't go overboard on this... really more for you to have a baseline of the noise floor through the chain once proper gain staging is in place.

* There is one last test on the DX3->A30Pro that could be interesting:

• Setup configuration as your original picture. Then disconnect the audio cable from the DX3, leave the cable in place, but unplug and completely remove the DX3 itself. This test is just to confirm that the audio cable is not acting as an antennae itself completely independent of the DX3 input. Note: the answer should (must) be no! Otherwise, you would have had the same humming on the test where you had the L30II instead of the DX3 and the audio cable disconnected from the L30II.

 

[Alalla]

• Potential other diagnostic step: route the DX3 to another headphone amp (e.g., DX3 -> L30II) instead of the A30Pro and follow the same testing tests and confirm that the other headphone amp likewise is picking up this humming issue under the same circumstances. If it does not, I'm at a loss since that would indicate some other interaction is at play.
  
  there is no buzzing when the RCA cables are plugged in the dx3 but once i unplug at least one of them and leave it next to the dx3pro i can hear the humming.
• 
  Setup configuration as your original picture. Then disconnect the audio cable from the DX3, leave the cable in place, but unplug and completely remove the DX3 itself. This test is just to confirm that the audio cable is not acting as an antennae itself completely independent of the DX3 input. Note: the answer should (must) be no! Otherwise, you would have had the same humming on the test where you had the L30II instead of the DX3 and the audio cable disconnected from the L30II.

no humming or buzzing. The A30pro amp only makes noise when i switch from GND/ to LIFT/ ( the switch on the back of the A30)


I did more tests and noticed buzzing when i was using SMSL su1 instead of dx3.
Strangely the buzzing disappeared once i powered the SMSL off of a portable powerbank. (the one you use to charge your phone 5v 2A)

I am not sure if its important put the A30pro that i received came with an Chinese / Australian plug. Not sure if topping makes different kind of version depending on the location.

 

[Chrise36]

• Potential other diagnostic step: route the DX3 to another headphone amp (e.g., DX3 -> L30II) instead of the A30Pro and follow the same testing tests and confirm that the other headphone amp likewise is picking up this humming issue under the same circumstances. If it does not, I'm at a loss since that would indicate some other interaction is at play.
  
  there is no buzzing when the RCA cables are plugged in the dx3 but once i unplug at least one of them and leave it next to the dx3pro i can hear the humming.
• 
  Setup configuration as your original picture. Then disconnect the audio cable from the DX3, leave the cable in place, but unplug and completely remove the DX3 itself. This test is just to confirm that the audio cable is not acting as an antennae itself completely independent of the DX3 input. Note: the answer should (must) be no! Otherwise, you would have had the same humming on the test where you had the L30II instead of the DX3 and the audio cable disconnected from the L30II.

no humming or buzzing. The A30pro amp only makes noise when i switch from GND/ to LIFT/ ( the switch on the back of the A30)


I did more tests and noticed buzzing when i was using SMSL su1 instead of dx3.
Strangely the buzzing disappeared once i powered the SMSL off of a portable powerbank. (the one you use to charge your phone 5v 2A)

I am not sure if its important put the A30pro that i received came with an Chinese / Australian plug. Not sure if topping makes different kind of version depending on the location.

There could be grounding issues in your place. Power the sources with battery and use optical or usb isolators to reduce the noise. Use the amps alone away from switching power supplies.

 

[Alalla]

There could be grounding issues in your place. Power the sources with battery and use optical or usb isolators to reduce the noise. Use the amps alone away from switching power supplies.

Went to my neighbors house, made myself at home and tried the same thing as i did at my house. I got the exact same results and the only fix was running the DAC off a battery.

 

[rcstevensonaz]

Went to my neighbors house, made myself at home and tried the same thing as i did at my house. I got the exact same results and the only fix was running the DAC off a battery.

Have you tried several different power suppliers for the DX3? And perhaps obviously, are you sure the power supply you are using for the DAC is set for your country's voltage / frequency.

 

[Alalla]

Have you tried several different power suppliers for the DX3? And perhaps obviously, are you sure the power supply you are using for the DAC is set for your country's voltage / frequency.

yeah. i tried. Pretty sure it is for European use.

 

[Alalla]

DX3

L30

 

[Alalla]

I also tried running the dx3 off of this:

got the same results

 

[Chrise36]

Went to my neighbors house, made myself at home and tried the same thing as i did at my house. I got the exact same results and the only fix was running the DAC off a battery.

Talk with Topping support unless you want to use the DAC with power bank(s)

 

[Alalla]

Talk with Topping support unless you want to use the DAC with power bank(s)

I have sent it back to the store, see what they think of it. Though i had the same problem with the SMSL su1. The only think i can do now is to try getting new cables and try to find some very clean DC power source. Or just call a priest to exorcise the evil spirits from my audio equipment.

 

[usern]

Try a DAC with balanced line connections and cables. They are more robust against noise issues than RCA cables.

 

[rcstevensonaz]

Try a DAC with balanced line connections and cables. They are more robust against noise issues than RCA cables.

Response — Part 1. Since you have the A30Pro headphone amp (as noted by @usern), you could look at the TOPPING D10B for the USB DAC, which can then also feed S/PDIF optical or coax out to other devices in your audio chain. That is what I have in my configuration for my headphone chain. However, note that the A30PRO is designed primarily for unbalanced input, so there is no real audio benefit unless you want the high voltage audio signal being pushed to the A30Pros.

Response — Part 2. A DAC should not be sending out enough RF interference to induce humming in nearby RCA cable that isn't even connected to the device. I think returning it was the right choice.

Response — Part 3. However, this does raise the question of what type of RCA cables are being used. The RCA cable should be using an appropriate shielded coax cable, not twisted pair. But even still, the DX3 shouldn't be adding that much hum in the test case where the cable is not close but not connected to the unit.

And for what it is worth, nearly all of my home audio environment is now balanced cables. But that is only because of the professional audio components in my setup — including an analog stereo mixer, RME ADI-2 Pro, and Neumann KH 120A speakers. Even before, when I was initially setup just using unbalanced RCA cables for all of the interconnects between those devices in a very crowded AV cabinet with a lot of other gear, I have never had any humming or hissing (after having moved my USB laptop over to the same circuit main as the AV rack to eliminate a ground noise issue).

 

[Alalla]

Response — Part 1. Since you have the A30Pro headphone amp (as noted by @usern), you could look at the TOPPING D10B for the USB DAC, which can then also feed S/PDIF optical or coax out to other devices in your audio chain. That is what I have in my configuration for my headphone chain. However, note that the A30PRO is designed primarily for unbalanced input, so there is no real audio benefit unless you want the high voltage audio signal being pushed to the A30Pros.

Response — Part 2. A DAC should not be sending out enough RF interference to induce humming in nearby RCA cable that isn't even connected to the device. I think returning it was the right choice.

Response — Part 3. However, this does raise the question of what type of RCA cables are being used. The RCA cable should be using an appropriate shielded coax cable, not twisted pair. But even still, the DX3 shouldn't be adding that much hum in the test case where the cable is not close but not connected to the unit.

And for what it is worth, nearly all of my home audio environment is now balanced cables. But that is only because of the professional audio components in my setup — including an analog stereo mixer, RME ADI-2 Pro, and Neumann KH 120A speakers. Even before, when I was initially setup just using unbalanced RCA cables for all of the interconnects between those devices in a very crowded AV cabinet with a lot of other gear, I have never had any humming or hissing (after having moved my USB laptop over to the same circuit main as the AV rack to eliminate a ground noise issue).

What other dacs would be recommend for the A30pro. Btw i ordered the D10b after i sent the dx3 back. I am not getting enough volume with my smsl out of the A30pro. only if i use it with the L30 pre amp.