Loud popping noises from Topping Pre90

[Neufneuf]

Hello everyone! I am a huge fan of this forum and many of my purchasing decisions were influenced by it - And so far, I am really happy!

I usually stream to my MiniDSP SHD, connected to a Hypex nCore Amp via XLR and KEF R3, which works great. But sometimes, I like to listen to Vinyl. My turntable is connected to a Cambridge Audio Duo, which is then connected to my SHD via RCA.

Today, I wanted to see what my Phono signal would sound like if I bypass my SHD. I got a Topping Pre90 and planned to connect my Phono Pre to the Pre90 and that via XLR to the Hypex.

I just took the RCA cables from my Phone Pre, that were in my SHD, and plugged them into the Pre90, and then I took the XLR cables that connected the SHD to the Hypex and also plugged them into the Pre90.

I turned on the 90 and the Hypex (My phono was turned off the entire time) and the 90 was preset to RCA input (Good) and RCA output, so I changed it to XLR output.

The moment I did that, I heard a very loud popping noise (Thought that might be normal on the switching), but then, about two seconds later, I heard another loud pop. I turned the Hypex off, turned the volume on the 90 as far down as possible, turned the Hypex on again and got another loud pop.

I turned the Hypex off again, turned the 90 off as well, waited a few seconds and then I turned the 90 on again and afterwards the Hypex - Another very loud pop.

After that, I just turned both off, removed the 90 and ran the system as usual, to see if my speakers are alright - It seems that nothing happened to them, but I still panicked quite a bit.

So, my question is: Did I make a mistake? Or might there be something wrong with the Pre90?

 

[restorer-john]

So, my question is: Did I make a mistake? Or might there be something wrong with the Pre90?

Quite possibly there's a problem with the Popping Topping. You could have a DC offset or transient spike issues on the outputs. Hopefully the Pre90 is NOT DC coupled on the output- but anything is possible with that brand.

Connect the Pre-90 to the amplifier and nothing else except speakers. Turn on the Pre-90 and wait 10 seconds, then turn on the power amplifier/s. If there's any nasty pops in that situation then you likely have an issue with the Pre-90.

 

[Neufneuf]

Quite possibly there's a problem with the Popping Topping. You could have a DC offset or transient spike issues on the outputs. Hopefully the Pre90 is NOT DC coupled on the output- but anything is possible with that brand.

Connect the Pre-90 to the amplifier and nothing else except speakers. Turn on the Pre-90 and wait 10 seconds, then turn on the power amplifier/s. If there's any nasty pops in that situation then you likely have an issue with the Pre-90.

Thank you so much for the reply!

But, if it is indeed having DC problems, couldn’t that damage my speakers if I try it out again? Is there any way to find it out without risking damage? If there isn’t, I will probably just return the Pre90.

 

[restorer-john]

Briefly testing is fine. If you are worried, use some sacrificial speakers.

The trouble with intermittent noises/faults is reliably demonstrating it. You may send the pre90 back and the seller might say “there’s nothing wrong with the unit”.

Just to clarify, the Hypex amp produces no noises on its own during power up/down and in the first few minutes?

 

[Neufneuf]

Briefly testing is fine. If you are worried, use some sacrificial speakers.

The trouble with intermittent noises/faults is reliably demonstrating it. You may send the pre90 back and the seller might say “there’s nothing wrong with the unit”.

Just to clarify, the Hypex amp produces no noises on its own during power up/down and in the first few minutes?

Well, I still have some other speakers, maybe I‘ll try it with those - Especially if one single test might be fine.

Sending it back would definitely not be a problem, I can just send back any online order without reason. But it sounds like that probably isn’t the case in other regions?

The Hypex only produces a slight, pretty quiet thump when I turn it on/off and is dead silent afterwards. But the noises I got from the 90 were not only LOUD (Even when I had the volume turned down as far as possible) but recurring. I never had anything like that happen before. I am still contemplating if my eyes might have played a trick on me, but when I tried it for the third time I felt like I saw a little bit of lightning in my peripherals when I turned it on.

 

[restorer-john]

Well, I still have some other speakers, maybe I‘ll try it with those - Especially if one single test might be fine.

Sending it back would definitely not be a problem, I can just send back any online order without reason. But it sounds like that probably isn’t the case in other regions?

The Hypex only produces a slight, pretty quiet thump when I turn it on/off and is dead silent afterwards. But the noises I got from the 90 were not only LOUD (Even when I had the volume turned down as far as possible) but recurring. I never had anything like that happen before. I am still contemplating if my eyes might have played a trick on me, but when I tried it for the third time I felt like I saw a little bit of lightning in my peripherals when I turned it on.

It does sound like the Pre90 likely has a problem. The thing with loud noises like you have experienced means you won't trust the unit to not do it again. And you'd be fighting an uphill battle trying to gain compensation for consequential damage if the Topping caused speaker damage by sending transients through your amplifier.

Good luck.

 

[pma]

I once had a similar issue with preamp + NC252MP. One of the preamp channels sometimes, after occurence of transient in mains line, went to oscillations in one channel which also resulted in a DC output component. The Hypex module got crazy with loud noise from one speaker. I have it documented by measurements. Hypex amplifies from DC, so it was even worse than in case of the amp with input capacitor.

 

[restorer-john]

I once had a similar issue with preamp + NC252MP. One of the preamp channels sometimes, after occurence of transient in mains line, went to oscillations in one channel which also resulted in a DC output component. The Hypex module got crazy with loud noise from one speaker. I have it documented by measurements. Hypex amplifies from DC, so it was even worse than in case of the amp with input capacitor.

That’s an interesting one. Did it oscillate and latch up?

 

[tuga]

If you are worried, use some sacrificial speakers.

Bloody hell!

 

[AdamG]

Hello everyone! I am a huge fan of this forum and many of my purchasing decisions were influenced by it - And so far, I am really happy!

I usually stream to my MiniDSP SHD, connected to a Hypex nCore Amp via XLR and KEF R3, which works great. But sometimes, I like to listen to Vinyl. My turntable is connected to a Cambridge Audio Duo, which is then connected to my SHD via RCA.

Today, I wanted to see what my Phono signal would sound like if I bypass my SHD. I got a Topping Pre90 and planned to connect my Phono Pre to the Pre90 and that via XLR to the Hypex.

I just took the RCA cables from my Phone Pre, that were in my SHD, and plugged them into the Pre90, and then I took the XLR cables that connected the SHD to the Hypex and also plugged them into the Pre90.

I turned on the 90 and the Hypex (My phono was turned off the entire time) and the 90 was preset to RCA input (Good) and RCA output, so I changed it to XLR output.

The moment I did that, I heard a very loud popping noise (Thought that might be normal on the switching), but then, about two seconds later, I heard another loud pop. I turned the Hypex off, turned the volume on the 90 as far down as possible, turned the Hypex on again and got another loud pop.

I turned the Hypex off again, turned the 90 off as well, waited a few seconds and then I turned the 90 on again and afterwards the Hypex - Another very loud pop.

After that, I just turned both off, removed the 90 and ran the system as usual, to see if my speakers are alright - It seems that nothing happened to them, but I still panicked quite a bit.

So, my question is: Did I make a mistake? Or might there be something wrong with the Pre90?

Welcome Aboard @Neufneuf !

 

[restorer-john]

Bloody hell!

Every audiophile, HiFi nut, technician and designer should have several pairs of ratty old sacrificial speakers. I always have a pair or two under my lab bench for testing. If an unstable/intermittent amplifier you think you fixed goes bad, it doesn't matter. If an amplifier bursts into oscillation and smokes up a tweeter- who cares.

Luckily for my sacrificial speakers, they tend to live for decades. My last pair went to the scrapheap just because I couldn't stand the look of their cabinets- not that they had failed. (old SEAS drivers are tough)

 

[pma]

That’s an interesting one. Did it oscillate and latch up?

Hi John, it oscillated, but did not latch up (the preamp). Below please see screenshots taken at the output of NC252MP in both situations

1. Everything OK, preamp does not oscillate. Blue = Lch, Yellow = Rch

2. Left channel preamp oscillates. See +1.4V DC shift at NC252MP output (blue). Plus whistles - not seen here in 2us/div

Too bad that Hypex DC output prot. is set at 10V.

 

[Sokel]

Do you have a DMM (even a cheap one)?
You can measure the outputs of your pre without connecting it to your amp,it will show what's happening.

 

[pma]

Do you have a DMM (even a cheap one)?
You can measure the outputs of your pre without connecting it to your amp,it will show what's happening.

That"s a good advice, I concur. However, it would not show preamp HF oscillations, usually >>1MHz. The result of oscillations, in my case, was rectification (ac ==> dc) at the Hypex input and thus the output DC shift + whistles (HF demodulation).

 

[Sokel]

That"s a good advice, I concur. However, it would not show preamp HF oscillations, usually >>1MHz. The result of oscillations, in my case, was rectification (ac ==> dc) at the Hypex input and thus the output DC shift + whistles (HF demodulation).

Agree but as long as it hears it (and so loud) that will be clearly visible on the DMM,either DC or AC (he better measure it with both modes).
If the pinout is the usual he must measure 1-2 and 1-3. (1 is the left pin,2 is the right and 3 is bottom one.I'm writing this for our friend here,not for you pma!)

 

[pma]

Agree but as long as it hears it (and so loud) that will be clearly visible on the DMM,either DC or AC (he better measure it with both modes).

Maybe, it is not for sure. He may also measure at Hypex output, without speakers connected. It would be absolutely safe, Hypex does not need the load connected for proper function. This would be my advice. Measure (with DMM, AC and DC) at the Hypex output terminals with speakers disconnected.

 

[Sokel]

It would be absolutely safe, Hypex does not need the load connected for proper function. This would be my advice. Measure (with DMM, AC and DC) at the Hypex output terminals with speakers disconnected.

I didn't know that Hypex is safe that way,so is even better and easier!
(but it wouldn't hurt to also measuring Topping by it's own,it could isolate the problem if would become visible on the DMM)

 

[Joel G]

Hello everyone! I am a huge fan of this forum and many of my purchasing decisions were influenced by it - And so far, I am really happy!

I usually stream to my MiniDSP SHD, connected to a Hypex nCore Amp via XLR and KEF R3, which works great. But sometimes, I like to listen to Vinyl. My turntable is connected to a Cambridge Audio Duo, which is then connected to my SHD via RCA.

Today, I wanted to see what my Phono signal would sound like if I bypass my SHD. I got a Topping Pre90 and planned to connect my Phono Pre to the Pre90 and that via XLR to the Hypex.

I just took the RCA cables from my Phone Pre, that were in my SHD, and plugged them into the Pre90, and then I took the XLR cables that connected the SHD to the Hypex and also plugged them into the Pre90.

I turned on the 90 and the Hypex (My phono was turned off the entire time) and the 90 was preset to RCA input (Good) and RCA output, so I changed it to XLR output.

The moment I did that, I heard a very loud popping noise (Thought that might be normal on the switching), but then, about two seconds later, I heard another loud pop. I turned the Hypex off, turned the volume on the 90 as far down as possible, turned the Hypex on again and got another loud pop.

I turned the Hypex off again, turned the 90 off as well, waited a few seconds and then I turned the 90 on again and afterwards the Hypex - Another very loud pop.

After that, I just turned both off, removed the 90 and ran the system as usual, to see if my speakers are alright - It seems that nothing happened to them, but I still panicked quite a bit.

So, my question is: Did I make a mistake? Or might there be something wrong with the Pre90?

Hi @Neufneuf , I am experiencing similar problems with my Pre90, they began yesterday morning out of the blue, until then it had been working perfectly for the almost 2 weeks I have had it. So popping happened: volume made pops, specially in some certain db numbers, changing source made pops, turning on and off made pop, and even trying to be ahead and turning my Purifi based amp before the Pre90 gave a loud pop. It was connected via xlr, tried rca and same problem. I disconnected it and wrote audiophonics customer service so hopefully they can help me returning the unit soon. Still quite annoying since i was happy with the unit until then