Topping A70 Pro HP & Preamp Review

[Antagron]

I just received my A70pro yesterday and am noticing that a couple times every minute, I hear a relay and the sound stops (display Vu/FFT continues to work) and then it comes back. Is this a bad setting somewhere or has anyone else experienced this? Driving via XLR from ADI-2 DAC and outputting to Edition XS over XLR.

 

[staticV3]

I just received my A70pro yesterday and am noticing that a couple times every minute, I hear a relay and the sound stops (display Vu/FFT continues to work) and then it comes back. Is this a bad setting somewhere or has anyone else experienced this? Driving via XLR from ADI-2 DAC and outputting to Edition XS over XLR.

Your RME's Line outputs are DC coupled and do not offer DC protection by default.
It's possible that the files you're listening to have a DC offset, which the RME is passing onto the A70 Pro, which in turn detects DC and momentarily mutes the output.

Your RME should have a function called DC Protection, which can be set to ON, OFF, or Filter.
Setting this to Filter might get rid of the sound interruptions.

 

[Antagron]

Your RME's Line outputs are DC coupled and do not offer DC protection by default.
It's possible that the files you're listening to have a DC offset, which the RME is passing onto the A70 Pro, which in turn detects DC and momentarily mutes the output.

Your RME should have a function called DC Protection, which can be set to ON, OFF, or Filter.
Setting this to Filter might get rid of the sound interruptions.

Thank you! I am hoping this is something tweakable and not a faulty unit. It seems my RME is already set to filter. Would "ON" help? I've never understood this setting, and the manual, if I recall, didn't explain it satisfactorily. Is there any other setting on the RME side that I could possibly tweak? Would it be better to run SE outputs instead of XLR, for example?

 

[Ahmonge]

Couple times every minute seems to me to be due to a defective unit.

 

[Moscardo]

I just received my A70pro yesterday and am noticing that a couple times every minute, I hear a relay and the sound stops (display Vu/FFT continues to work) and then it comes back. Is this a bad setting somewhere or has anyone else experienced this? Driving via XLR from ADI-2 DAC and outputting to Edition XS over XLR.

Try to disconnect outputs and see if it happens again, to find if the problem is on the outputs or inputs. Then try to connect another source and/or another headphone.

 

[staticV3]

Thank you! I am hoping this is something tweakable and not a faulty unit. It seems my RME is already set to filter. Would "ON" help? I've never understood this setting, and the manual, if I recall, didn't explain it satisfactorily. Is there any other setting on the RME side that I could possibly tweak? Would it be better to run SE outputs instead of XLR, for example?

ON with mute the RME's output once it detects DC.
Filter will filter out DC in the audio before it is converted to analog.

Whether you use RCA or XLR to connect to the A70Pro should not make a difference.

 

[Antagron]

Try to disconnect outputs and see if it happens again, to find if the problem is on the outputs or inputs. Then try to connect another source and/or another headphone.

I hooked up my iPhone through the Apple dongle -> 3.5mm -> RCA cable, and so far it's running flawlessly. I think maybe this is on the RME side? I can try running the SE outputs from RME and see if that makes a difference?

 

[Moscardo]

I hooked up my iPhone through the Apple dongle -> 3.5mm -> RCA cable, and so far it's running flawlessly. I think maybe this is on the RME side? I can try running the SE outputs from RME and see if that makes a difference?

Sure, but as of now you can rule out problems on the headphones and concentrate on the inputs. Try also another XLR cable, if available.

 

[Antagron]

Sure, but as of now you can rule out problems on the headphones and concentrate on the inputs. Try also another XLR cable, if available.

So, as a follow-up, I now have the RME hooked up by SE and XLR. Both SE and XLR trigger the relays. I don't have another XLR cable unfortunately, but it worked fine on my previous THX 789 amp for the month I've had the RME. What I did do is turn down the RME volume to -20 with AutoRef level on (+7) and it still cuts out, but less frequency. Is it possible that I have the volume coming out of the RME too high? I can try to keep dropping the volume on the RME side and see if it mitigates the muting on the A70. I thought I was supposed to be able to run the RME at "+0" though? (I admit I'm confused by the output level and the AutoRef level and dbR and dbU....)

 

[staticV3]

So, as a follow-up, I now have the RME hooked up by SE and XLR. Both SE and XLR trigger the relays. I don't have another XLR cable unfortunately, but it worked fine on my previous THX 789 amp for the month I've had the RME. What I did do is turn down the RME volume to -20 with AutoRef level on (+7) and it still cuts out, but less frequency. Is it possible that I have the volume coming out of the RME too high? I can try to keep dropping the volume on the RME side and see if it mitigates the muting on the A70. I thought I was supposed to be able to run the RME at "+0" though? (I admit I'm confused by the output level and the AutoRef level and dbR and dbU....)

You can run the RME at at least 4Vrms via XLR. That's 12dBV or 14.2dBu.
I'll let you figure out how to setup the RME accordingly.

Though I highly recommend a multimeter for all things analog audio. Can be immensely helpful in situations like this.

 

[Antagron]

You can run the RME at at least 4Vrms via XLR. That's 12dBV or 14.2dBu.
I'll let you figure out how to setup the RME accordingly.

Though I highly recommend a multimeter for all things analog audio. Can be immensely helpful in situations like this.

Would the output level of the RME somehow affect the A70? Or some other setting? I've tried a bunch of music and it triggers the relay mute, so I doubt it's related to the content I'm playing.

 

[staticV3]

Would the output level of the RME somehow affect the A70?

Sure, a too high output level may clip the A70Pro's input.
Or, depending on what gain your A70Pro is set to, it may clip the output.

Or some other setting?

Yes. For example the DC Protection setting.

 

[Moscardo]

So, as a follow-up, I now have the RME hooked up by SE and XLR. Both SE and XLR trigger the relays. I don't have another XLR cable unfortunately, but it worked fine on my previous THX 789 amp for the month I've had the RME. What I did do is turn down the RME volume to -20 with AutoRef level on (+7) and it still cuts out, but less frequency. Is it possible that I have the volume coming out of the RME too high? I can try to keep dropping the volume on the RME side and see if it mitigates the muting on the A70. I thought I was supposed to be able to run the RME at "+0" though? (I admit I'm confused by the output level and the AutoRef level and dbR and dbU....)

in the RME specifications, you can find

• Output level switchable +19 dBu, +13 dBu, +7 dBu, +1 dBu @ 0 dBFS

so you probably are using the 7 dBu setting which corresponds to 1.7 Vrms. This level is perfectly acceptable by the A70. As a matter of fact, also the maximum level, 19 dBu 6.9 Vrms should not be a problem, as in A70 specifications an input as high as 9.8 Vrms is indicated at low gain.

You definitely need to check if RME has a problem at the outputs, as only a significant DC could explain such behavior. As you verified that A70 RCA input works fine with the phone as a source, the problem is more probably at the RME side.

 

[Antagron]

Sure, a too high output level may clip the A70Pro's input.
Or, depending on what gain your A70Pro is set to, it may clip the output.

Yes. For example the DC Protection setting.

• RME
  • Line Out
    • Volume: -20 dBr
    • Ref Level Auto (+1 dbU)
    • DC Protection = Filter
    • Loudness/PEQ/BT = Off
  • Device
    • Mute Line = vs Phones
• A70
  • Input = SE
  • Gain = Low
  • Volume = -30.0

This triggers the relays! These should be pretty tame settings, no?

 

[Moscardo]

So, as a follow-up, I now have the RME hooked up by SE and XLR. Both SE and XLR trigger the relays. I don't have another XLR cable unfortunately, but it worked fine on my previous THX 789 amp for the month I've had the RME. What I did do is turn down the RME volume to -20 with AutoRef level on (+7) and it still cuts out, but less frequency. Is it possible that I have the volume coming out of the RME too high? I can try to keep dropping the volume on the RME side and see if it mitigates the muting on the A70. I thought I was supposed to be able to run the RME at "+0" though? (I admit I'm confused by the output level and the AutoRef level and dbR and dbU....)

have you tried only with RCA cable removing XLR one?

 

[Antagron]

Will try now. Yes, with XLR unplugged from A70, it still "mutes"... Also noticing that when it comes out of standby, it locks up occasionally saying DFU v2.01 ( I assume I got the latest firmware pre-installed?), and the only thing to fix it is to use the power switch on the back... anyone seen that?

 

[Ykar]

Hello Ykar, could you please tell us a bit more about the power amplifier you are using? I have just ordered the Topping A70pro and I'm planning to use it primarily as a preamp to my Boxem Arthur 4215/E2 Purifi Eigentakt power amplifier.

2 Ncore mono blocks (2xNC250MP). But l'm quite sure there's no issue with the power amp itself, I've fed it with several other devices and never had such issue. Sometimes a very gentle pop noise when triggering on / off, but nothing like that.
Loud pop noise is every time the relay for XLR is triggered on (back from mute, switching input or output)

I have no problems in balanced mode with xlr mogami cables connected to a rotel rb1582mkii

Thanks
I've tried switching XLR cables, both from source input and from output to amp but no luck, pop noise always coming from A70's mostly from its left channel.

I have the FW v1.07 tho, so I guess the update was done by audiophonics as well as the seal on the box itself on your unit @Ykar.

Bought from Amazon FR : CN seller but EU stock shipped by Amazon. A70 box arrived sealed in a a plastic film, it really looked like it was never opened since out from factory, but that may be a seller trick.

Anyway, I'll send it back as I can't stand those nasty pops but I'm trying to figure out if that's a faulty unit or if should look for some other pre-amp. Other than that everything is working flawlessly. I may try a silver unit if that can bring me good luck

 

[abc1234]

2 Ncore mono blocks (2xNC250MP). But l'm quite sure there's no issue with the power amp itself, I've fed it with several other devices and never had such issue. Sometimes a very gentle pop noise when triggering on / off, but nothing like that.
Loud pop noise is every time the relay for XLR is triggered on (back from mute, switching input or output)


Thanks
I've tried switching XLR cables, both from source input and from output to amp but no luck, pop noise always coming from A70's mostly from its left channel.


Bought from Amazon FR : CN seller but EU stock shipped by Amazon. A70 box arrived sealed in a a plastic film, it really looked like it was never opened since out from factory, but that may be a seller trick.

Anyway, I'll send it back as I can't stand those nasty pops but I'm trying to figure out if that's a faulty unit or if should look for some other pre-amp. Other than that everything is working flawlessly. I may try a silver unit if that can bring me good luck

I too have a similar problem. I am using d70 pro octo -> a70 pro -> pa7+ connected with XLR and 12V trigger.

In my case, a popping sound comes from both speakers when the power is turned on, and a popping sound comes from the right channel when I switch between headphones and speakers using the remote control. And there is a small pop sound periodically from the right channel.

Topping has determined that the product is not normal and will be exchanging it.

 

[Ykar]

Not sure if this is proving anything but at least I had some fun with REW's oscilloscope, I didn't even knew that tool existed.

Noise detected at the time of un-muting A70 Pro RCA out. Barely visible.

Noise from Right XLR out at un-muting time :

And same from Left XLR out :

 

[Moscardo]

How did you acquire those signals?