Topping D90 XLR output: inverted polarity?

[theREALdotnet]

Hi, I’ve just signed up after years of lurking.

I‘ve usually been able to get my answers from ASR just by reading, but for this particular question I haven’t found an answer. That could well be due to my lacking search-fu, but believe me, I’ve tried.

So here it goes: I’ve got a Topping D90 (AKM model without MQA) that I hook up to my amp via XLR and to an active sub via RCA. I’ve been playing a lot with speaker and sub placement to wrestle with the challenges of my smallish room, and have made use of the phase adjustment (0-180º) of the sub a fair bit. Recently I have arrived at a sub placement that puts it at pretty much the same distance from the listener as the main speakers. I was puzzled to find that the best sub phase adjustment for that position was 180º. After blaming the sub for a while I decided to take some measurements and found that the XLR output of the D90 has the reverse polarity of the RCA output and, in fact, of the input. I did not see that mentioned in the manual. An email query to Topping about this went unanswered.

I’m wondering whether this is a known characteristic of the D90, whether I have got a faulty unit or whether I‘ve messed up the settings somehow (not that I could find any that deal with output polarity).

 

[RickSanchez]

You can go to the Topping D90 review thread, then click Search. In the search box type in "polarity" (without the double quotes) and then choose "This thread" in the drop-down box to the right. You'll get results like this that should answer your question:

Topping D90 Balanced USB DAC Review

My D70 behaves equally as the D90 when it comes to device control and behavior. Unfortunately, display burns are inevitable on these devices. For sure I will never again buy a device whose display cannot be turned off completely. Also have the D50s and it behaves as it should considering it also...

www.audiosciencereview.com

Topping D90 Balanced USB DAC Review

My D70 behaves equally as the D90 when it comes to device control and behavior. Unfortunately, display burns are inevitable on these devices. For sure I will never again buy a device whose display cannot be turned off completely. Also have the D50s and it behaves as it should considering it also...

www.audiosciencereview.com

 

[theREALdotnet]

Thank you Rick. As a D90 owner I’m naturally quite familiar with that thread, and I have seen the posts you’ve linked. I don’t think they talk about the same thing that I’m taking about.

The question “is the D90 differentially balanced (outputting inverted polarity) or not?”, as I read it, is about whether the balanced output is made up of two complementary signals (inverted with respect to each other). It is, of course. However, the polarity of the (+) lead (XLR pin 2) should follow the input wave form, and also be the same as the signal (centre pin) lead of the RCA connector.

What I’m seeing on my D90 is that XLR pin 2 is the inverse of the input signal, and of the RCA centre pin.

 

[RickSanchez]

Thanks for the clarification. @JohnYang1997 may be able to answer that question for you.

 

[theREALdotnet]

Hm, so either

• the Topping D90 is a lot less popular than I thought,
• nobody has noticed the inverted XLR polarity on their D90 or
• this only affects my D90.

 

[kmsolo]

Hm, so either

• the Topping D90 is a lot less popular than I thought,
• nobody has noticed the inverted XLR polarity on their D90 or
• this only affects my D90.

HI,I met a situation similar to yours. I am learning the REW software. Yesterday I tested my d90mqa. The phase of XLR output is different from RCA output. I am also looking for the answer.

 

[maarvold]

I am about to acquire my 4th Topping D90; I use them in my studio for various tasks. I haven't checked all of them, but it took me a little head-scratching before I figured out that the first one I bought was Pin 3 = High. Almost all modern audio gear these days is Pin 2 = High (3 = Low and 1 = Ground/Shield). So, by comparison to modern audio gear, the XLR outputs of the D90 are out of absolute polarity.

 

[UCrazyKid]

Hm, so either

• the Topping D90 is a lot less popular than I thought,
• nobody has noticed the inverted XLR polarity on their D90 or
• this only affects my D90.

I would venture to guess that few people with the D90 are using the XLR and the RCA simultaneously, as the unit is very popular here. When using it in my 2.1 system, I simply ran my sub off of the RCA daisy chain connections provided by my power amplifier. So I did not run into this issue.

 

[maarvold]

I would venture to guess that few people with the D90 are using the XLR and the RCA simultaneously, as the unit is very popular here. When using it in my 2.1 system, I simply ran my sub off of the RCA daisy chain connections provided by my power amplifier. So I did not run into this issue.

Being in absolute polarity refers to the ability of a component to pass a compression wave as a compression wave, instead of turning it into a rarefaction wave. Simplified, a 'punchy' kick drum should push on your chest instead of pulling on it. There is a 2 box system called a Galaxy Cricket that can test for absolute polarity in all kinds of situations. Be aware that speaker manufacturers sometimes flip the absolute polarity/phase on one or more drivers to attempt to get smoother/subjectively flatter frequency response. I personally prefer when the largest driver is in absolute phase/polarity. Some people say absolute polarity doesn't matter sonically. Whether one believes that or not, my preference is for output to be as close to input as possible.

 

[pLudio]

I generated a WAV file in Python with a truncated sine that looks like this in Audacity

and used the oscillscope in REW with Topping D90 (no MQA) XLR connected to a Behringer UMC204HD.

Looks fine. I haven't got a converter cable for RCA to XLR yet so don't know how that looks. It's possible that the UMC204HD is also inverted.

 

[theREALdotnet]

I used a tone burst signal generated by REW and measured with an actual oscilloscope at both the RCA and XLR outputs of the D90. The RCA signal was inverted, the XLR signal was not.