Topping A30Pro Review (Balanced Headphone Amp)

[Fohdeesha]

OK, it's definitely a DC offset issue. Measuring the balanced output of my interface while playing back that problematic bloc party track, I get a whopping 3.5v of DC:

That's *really* bad - I did a quick scan of some of my library and the worst I could find otherwise was around 0.1vdc on some amateur soundcloud stuff. My best guess is the Topping is either going into DC detection/protection directly, or the DC offset in the signal is causing the amplifier to overload, and the Topping then goes into overload protection. I suppose that's nicer than the Topping just allowing it to happen unnoticed until the front end fries itself. Some clarification from Topping on this would be great.

So, warning: if you're lucky enough to have an interface with a DC-coupled output, (most high end converters, a lot of professional/recording interfaces), take note of what you're playing. If you find the Topping switching itself off and not coming back on until you stop playback - it's probably DC in your source material. Anyone brave enough to play back the Bloc Party track I linked on the last page should be able to recreate this without issue, it does seem to at least be harmless as it goes into protection (at least for now). And to the mastering engineer of this Bloc Party album, which peaked at #3 in UK Albums Charts at one point: give me some of that crack rock you were smoking

 

[VariousArtists]

OK, it's definitely a DC offset issue. Measuring the balanced output of my interface while playing back that problematic bloc party track, I get a whopping 3.5v of DC:

That's *really* bad - I did a quick scan of some of my library and the worst I could find otherwise was around 0.1vdc on some amateur soundcloud stuff. My best guess is the Topping is either going into DC detection/protection directly, or the DC offset in the signal is causing the amplifier to overload, and the Topping then goes into overload protection. I suppose that's nicer than the Topping just allowing it to happen unnoticed until the front end fries itself. Some clarification from Topping on this would be great.

So, warning: if you're lucky enough to have an interface with a DC-coupled output, (most high end converters, a lot of professional/recording interfaces), take note of what you're playing. If you find the Topping switching itself off and not coming back on until you stop playback - it's probably DC in your source material. Anyone brave enough to play back the Bloc Party track I linked on the last page should be able to recreate this without issue, it does seem to at least be harmless as it goes into protection (at least for now). And to the mastering engineer of this Bloc Party album, which peaked at #3 in UK Albums Charts at one point: give me some of that crack rock you were smoking

Thank you for getting to the bottom of this.

So my set up is just D30 Pro + A30 Pro, does that mean I do not need to worry about this problem?

 

[Fohdeesha]

Thank you for getting to the bottom of this.

So my set up is just D30 Pro + A30 Pro, does that mean I do not need to worry about this problem?

You would need to know if the D30 Pro's output is DC-coupled or AC-coupled. A cursory google search, I'm not finding an answer. If you have a multimeter you can just measure the output of the DAC while playing back something like the linked bloc party track (skip to the middle of it). Make sure your multimeter is set to measure DC, and you're measuring between pins 2 & 3 on the XLR output. If you measure 0.00 volts DC, it's AC-coupled and you don't have to worry about it

DC coupled outputs into amplifiers with DC coupled inputs isn't exactly a new or rare issue, I guess I just figured at the price of the Topping, it would be AC-coupled to deal with the higher end DACs that are typically DC coupled. In fact after some searching I'm seeing at least one headphone amp that has an internal dip switch to change it to AC-coupled, which is effectively a 12hz high pass filter. for example: https://www.audiosciencereview.com/forum/index.php?threads/ac-or-dc-coupling-in-headphone-amp.20280/

 

[JohnYang1997]

OK, very strange. After further investigating, it only happens with a specific song. And only at a certain volume (about halfway on the knob, medium gain). It shuts off after that point and will keep power cycling itself. If I back the volume down, it will stop power cycling and stay on. Here's a video:

The fact that it's only one specific track that's doing it makes me think it may be a negative reaction to DC offset? My interface is infact DC coupled (Ultralite AVB), so if a source recording does have DC components, they'll make it out of my interface intact. Is the Topping's front end getting overloaded past a certain gain point with DC present? Here's the track in question if anyone wants to play around themselves, it's completely unmodified from CD source material (other than lossless FLAC compression of course). Any DC present was in the source recording: https://fohdeesha.com/data/other/05 - Blue Light (Engineers 'Anti-Gravity' Mix).flac

EDIT: Confirmed that the above track has nearly 4 volts of DC offset, assuming your interface puts out around +20 dBu at 0dbFS. Playing that back through *any* amp is probably not the best idea, and Bloc Party needs to fire their mastering engineer

The DC protection senses the output of the amplifier which means it's after the volume control. So the volume surely matters.
The XLR balanced input is DC coupled while the RCA unbalanced input is AC coupled.

 

[JohnYang1997]

Thank you for getting to the bottom of this.

So my set up is just D30 Pro + A30 Pro, does that mean I do not need to worry about this problem?

DC from the recording is not going through D30pro. So you are fine.

 

[Volikovvv]

DC from the recording is not going through D30pro. So you are fine.

Hi! I'm own this only two days and it sound really great! Should i worry about problems described in previous post using SMSL SU-9? I connected them via XLR. As far as i understand, i should avoid using RCA with another dacs? For example i have Geek pulse x infinity, i should worry about connecting it with rca?
John are you developer of this great thing?
Actually after purchasing this amp, i started to think about re-evaluation of my previous dacs like m400, ares 2, because with Flux labs amplifier i did not liked them at all, i previously own fa-12s and fa-10pro, maybe this is the question of synergy with headphones, but in my opinion soundwise a30 pro better than both of them, but sadly not in build quality, switchers move to the left and right a little, and volume know feels a little bit cheap, i hope there will be no problems with that.

 

[JohnYang1997]

Hi! I'm own this only two days and it sound really great! Should i worry about problems described in previous post using SMSL SU-9? I connected them via XLR. As far as i understand, i should avoid using RCA with another dacs? For example i have Geek pulse x infinity, i should worry about connecting it with rca?
John are you developer of this great thing?
Actually after purchasing this amp, i started to think about re-evaluation of my previous dacs like m400, ares 2, because with Flux labs amplifier i did not liked them at all, i previously own fa-12s and fa-10pro, maybe this is the question of synergy with headphones, but in my opinion soundwise a30 pro better than both of them, but sadly not in build quality, switchers move to the left and right a little, and volume know feels a little bit cheap, i hope there will be no problems with that.

I wouldn't worry about it. It's really rare that a song has DC value over tens of millivolts let alone 3.5 Volts. And it's also attenuated by the volume control so in majority of the time it's absolutely fine. And when DC offset happens, it will protect your headphones.

 

[Fohdeesha]

The DC protection senses the output of the amplifier which means it's after the volume control. So the volume surely matters.
The XLR balanced input is DC coupled while the RCA unbalanced input is AC coupled.

Thanks! That's exactly the info I was looking for. So to be clear, there is dedicated DC current protection, and it's on the output to the headphones? So that would explain why it wasn't tripping when I had the volume all the way down, and tripped at a certain volume about halfway up. Good to know! false alarm

 

[JohnYang1997]

Thanks! That's exactly the info I was looking for. So to be clear, there is dedicated DC current protection, and it's on the output to the headphones? So that would explain why it wasn't tripping when I had the volume all the way down, and tripped at a certain volume about halfway up. Good to know! false alarm

Yep.

 

[liu]

The DC protection senses the output of the amplifier which means it's after the volume control. So the volume surely matters.

Good to see DC protection in action! Nice job done!

 

[Volikovvv]

John from what point of view, what is the best possible dac to use with this amp - D90? Su-9 is great pairing, just of curiosity.

 

[JohnYang1997]

John from what point of view, what is the best possible dac to use with this amp - D90? Su-9 is great pairing, just of curiosity.

Most of these DACs are a good match. D30pro for better looking stack.

 

[Volikovvv]

Most of these DACs are a good match. D30pro for better looking stack.

Thank you for advice
Very interested in photo of the amplifier board, but afraid to open my because of guarantee. Maybe somebody has the photos?

 

[Fernando]

Can someone explain what is the problem that the a30pro is having with a language for non-electronic experts? Thx

Earn SMSL positions?

 

[liu]

Very interested in photo of the amplifier board, but afraid to open my because of guarantee. Maybe somebody has the photos?

I'm interested too. Topping usually do not mind if you take it apart. there's no "do not remove" stickers on top of the screws. so feel free.

 

[Fohdeesha]

Can someone explain what is the problem that the a30pro is having with a language for non-electronic experts? Thx

Earn SMSL positions?

no problem - topping working correctly

 

[wyup]

A question: Using rca outs on the D/A30Pro stack, feeding balanced XLR from the dac to the headamp, which unbalanced RCA output would give the best quality, the headamp or the dac? In other words, which one would give the best balanced to unbalanced conversion?

 

[aandres_gm]

Dear 30Pro stack owners, where did you put your A30Pro, top or bottom? Topping's marketing material places it on the bottom, but all the perforations make me thing its place is on the top of the stack.

Got mine today, but unfortunately I won't get my XLR cables until Saturday, so the impressions will have to wait.

 

[Coin3]

A question: Using rca outs on the D/A30Pro stack, feeding balanced XLR from the dac to the headamp, which unbalanced RCA output would give the best quality, the headamp or the dac? In other words, which one would give the best balanced to unbalanced conversion?

Per the A30Pro's manual, RCA output will not act as a passthrough when feeding XLR input. I just tested this myself to confirm.

Dear 30Pro stack owners, where did you put your A30Pro, top or bottom? Topping's marketing material places it on the bottom, but all the perforations make me thing its place is on the top of the stack.

Got mine today, but unfortunately I won't get my XLR cables until Saturday, so the impressions will have to wait.

I put my A30Pro on top. It does get somewhat warm when outputting a lot of power, but it would probably be fine on bottom too. I mainly put it on top for better cable routing in my setup.

 

[Pan]

I have tried putting on top and bottom. I end up putting it on top cause when it is at the bottom, D30pro gets hot.