Regular, Sharp Pops Through Stereo

[avantbored]

Friends,

Just posted about my system for a different problem (crackling on input changes and volume pot), but here's a new one that I started tracking.

Managed to read some threads about this issue, so let me go through facts:

• Quick, assertive pop through the left and right speaker
• Irrespective of volume -- happens at 0 or 20 or 30.
  
• Irrespective of input -- phono or line
  
• At around ~10 minute intervals.

My neighborhood experienced a series of quick outages on Saturday (~2 hour intervals -- went off, came on, went off, came on, went off for longer as the city worked to fix it.)

• The power cut out twice during my listening session.
  
• I didn't know the power was going to behave as I described above, so while I thought the issue had settled, I turned the stereo back on, and then the power cut out again, when I decided just to leave it off.

Sunday: Fine. Yesterday: Also fine.

Tonight: Pops every ten minutes.

I found some threads describing that this could be a capacitor issue or a pre - driver transistor issue. I can follow technical jargon and concepts a bit, but I'm very much a beginner still. Just hoping for some other comments and insights into what I've described.

System:
Nakamichi pa7aii
Ca7a
Yamaha ns1000ms
Technics sl1700mk2
Blue sound node 2i into SMSL SU-8S

Thanks for your reading and your time.

EDIT #1:

I have continued testing with another unit (Yamaha CR820) and reproduced the problem. While I'm relieved that it is less likely now that it is my beloved Nak, I don't know if it's a problem with the speakers.

Currently running the CR820 with other speakers on same outlet in same room. I have not reproduced the problem with 820/NS100x combo on same outlet.

Blown tweeter?! NS1000Ms still sound clear.

 

[ivandezande]

You need to figure out which component is causing it by swapping or elimination.
It’s not a capacitor, whoever told you that is full of it.

 

[avionic]

I don't know if it's a problem with the speakers.

Currently running the CR820 with other speakers on same outlet in same room. I have not reproduced the problem with 820/NS100x combo on same outlet.

Blown tweeter?! NS1000Ms still sound clear.

If it pops with both speakers.. I seriously doubt that both speakers have the same identical problem.. Unless you or someone else has compoimised both NS-1000's in the same way.

 

[avantbored]

You need to figure out which component is causing it by swapping or elimination.
It’s not a capacitor, whoever told you that is full of it.

The investigation continues! I have the CR820/1000M combo running right now. No pop yet.

If it pops with both speakers.. I seriously doubt that both speakers have the same identical problem.. Unless you or someone else has compoimised both NS-1000's in the same way.

Well, I was suspecting that outage mentioned above. Like a situation where it nudged the tweeter close to breaking, and in the intervening days, it worsened? I will continue.


Was also talking to a nice dude who runs a shop near me (Zach at Blind Dog Hifi in Huntington Beach) that it might be good old static electricity.

 

[avantbored]

Update, everyone. I reproduced the problem with the PA7AII driving NS100X. Same pop, same interval!

Passing thought: The preamp has been finicky lately. In another thread, I mentioned scratchy balance pot, as well as occasional crackling in the volume control. Would a dirty pot be trying to rid itself of gunk produce this kind of intermittent pop?

I don't have another preamp to try, so tomorrow I will try to run my Bluesound Node straight to the amp and see if the problem persists.

Talking a bit out loud here, but there's also some talk about the Bluesound with an external DAC also making pop sounds when hooked to coax (my setup.) But the pop presented while I was in phono, so
don't know if that makes any diff.

EDIT 2:

I have reproduced the pop with PA7A II and NS100X on phono switch with no input, totally unplugged. Tomorrow going to try it on a different outlet altogether.

 

[elnaldo]

A video showing the noises would be helpful.

 

[avantbored]

A video showing the noises would be helpful.

Chain: CA7A --> PA7A II --> NS100X

The system has been on for about 30 minutes now. NO source components plugged into preamp, set to "Aux." Volume set to 0.

The video is a crop of a 6:37 video. The noise presents at 0:11. Ambient noise is street traffic (I'm right on the street and my windows are a little screwy -- long story.) Easier to hear if you've got headphones on.

In the video, it does sound like static discharge, like a snap.

https://drive.google.com/file/d/1N4VutbPdmBVyLkQnq47JHP0q-AiTC0Ok/view?usp=sharing


EDIT #3:

Here is an audio recording (move to 09:15; sound at 09:21).

I have switched from "Aux" to "Phono." The volume is still set to 0.

Phone microphone directly above tweeter of left speaker (but pop is in stereo -- I hear it in both speakers.)

https://drive.google.com/file/d/1NAlulca32rRk5DdjhE3ldpV09r0V9ap3/view?usp=sharing

 

[elnaldo]

It sounds like noisy transistors to me. But that fail is usually different in both channels, not both channels doing the same at the same time. Same noise at both channels points to the power supply. It could be a noisy transistor at the power supply. But double check with headphones if the noise is present in both channels at the same time.

 

[gadget73]

can't look at the vid here but if its the same in both channels I agree its unlikely to be a noisy transistor unless its in the supply

could be ailing power switch, or the pop suppressor across it. Some things use those Rifa capacitors across the power line which are somewhat infamous for cracking and failing. They eventually catch fire but before that they can arc across the foils and do goofy stuff.

 

[MuseChaser]

I admittedly just scanned this thread, so I may have missed a critical detail, but it sounds like a possible cause could be outside your stereo system, i.e., something else plugged in to the same circuit, or even another circuit, in your house cycling on or off and causing some form of momentary interference. Yes, ideally, your audio gear should filter it out, but that doesn't always happen. Anything in your house come to mind?

 

[avantbored]

I admittedly just scanned this thread, so I may have missed a critical detail, but it sounds like a possible cause could be outside your stereo system, i.e., something else plugged in to the same circuit, or even another circuit, in your house cycling on or off and causing some form of momentary interference. Yes, ideally, your audio gear should filter it out, but that doesn't always happen. Anything in your house come to mind?

Thanks for reading -- I do have an extant issue with this weird fluctuating warping sound (I see it present in kitchen hood lights flickering), but it does not sound like this pop. I haven't yet tested this in another room (another circuit), and your reply reminded me to move some stuff in the other room -- got distracted with grading papers!

 

[avantbored]

It sounds like noisy transistors to me. But that fail is usually different in both channels, not both channels doing the same at the same time. Same noise at both channels points to the power supply. It could be a noisy transistor at the power supply. But double check with headphones if the noise is present in both channels at the same time.

can't look at the vid here but if its the same in both channels I agree its unlikely to be a noisy transistor unless its in the supply

could be ailing power switch, or the pop suppressor across it. Some things use those Rifa capacitors across the power line which are somewhat infamous for cracking and failing. They eventually catch fire but before that they can arc across the foils and do goofy stuff.

Thanks to both of you for your insights on this. I have in mind two techs to call to get them to look at this. I will still report back to rule out that it's the circuit though, per MuseChaser's comment.

 

[avantbored]

Thanks for those still watching.

I set up the PA7A in another room, with the same setup as above (CA7 -> PA7 -> NS100X) and not a pop to be heard.

The CR820 hooked up to NS1000Ms. Nary a pop.

What does that leave? The outlet itself? I don't see any burn marks but maybe the outage combined with how hefty the amp is itself pushed it?

Those of you may have already inferred that there's a big diff between the CR820 and the Nak PA7A II -- 170 watts or so (55wpc to 225wpc respectively). This dwelling is a new construction so the circuit is 15A and the Nak has a 20A output current capability (per the manual: https://archive.org/details/manual_PA7AII_OM_NAKAMICHI_EN/page/n9/mode/2up).

There's a good tech out on the other side of town that the PA7 is with, and he wanted me to bring the CA7 to rule that one out too (I don't have an extra pre). The CA7 needed its balance pots and volume control cleaned, so why not? He's respected and has a fair fee.

 

[MuseChaser]

It leaves some other appliance on that circuit kicking on or off and causing a momentary burst of interference. It might be pain, but you could try setting up your system on that circuit again, but ENSURING that nothing else is plugged in or otherwise drawing from that circuit (i.e., something hardwired in. We have some smoke detectors that are hardwired, not that they'd typically create interference or surges). My hunch is that your system would be pop-free. Then, start plugging in all the various other drains on that circuit, listen for the pops each time you add something new. Pay special attention to anything that "cycles"... Fridge, A/C, dehumidifer, space heater, washing machine,....

 

[avantbored]

It leaves some other appliance on that circuit kicking on or off and causing a momentary burst of interference. It might be pain, but you could try setting up your system on that circuit again, but ENSURING that nothing else is plugged in or otherwise drawing from that circuit (i.e., something hardwired in. We have some smoke detectors that are hardwired, not that they'd typically create interference or surges). My hunch is that your system would be pop-free. Then, start plugging in all the various other drains on that circuit, listen for the pops each time you add something new. Pay special attention to anything that "cycles"... Fridge, A/C, dehumidifer, space heater, washing machine,....

Even with the other amp on? I believe when I wrote earlier that I was able to reproduce the pop, it may have been something else; the thing's been on now for several hours and there hasn't been a pop. So, I throw my hands up.

My dwelling is an open-plan space, and the fridge is on a different circuit, as is the A/C. I may be recalling incorrectly that an electrician who'd come by for a separate issue said that the fridge could still affect the circuit on which the stereo system is on; the design of the whole multi-unit development (single-family homes arranged in a townhouse factor) also might play a role in the larger scale (another electrician helped explain this, but I'm forgetting the reasoning).

I will try to test as you've advised once I get the amp back. If nothing else, it's $55 for peace of mind, and maybe a little more for the tech to clean the balance and volume pots. I did wince a little when he slid the top my amp across the smoothed wood counter -- I'm very protective of it! He comes highly recommended so I am not so worried.

 

[elnaldo]

Noisy transistors can be tricky. I had amps in my bench for weeks, and the day before to give it back to the owner, to tell him the amp was OK, the noise appeared. I'd let it some more time under test at the tech's shop. I'd tell him to listen for some days before giving it back.

Of course it could be some external interference, (specially if both channels do the same noise at the same time) but if it's a noisy transistor, in some cases it can work fine for weeks before showing the noises again. From my experience, in cold weather it fails more often, and in summer or hot environment, it can be silent for longer. I've seen an amp working fine all the summer and start to make noises after a very cold night.

 

[avantbored]

To those staying tuned in...

Noisy transistors can be tricky. I had amps in my bench for weeks, and the day before to give it back to the owner, to tell him the amp was OK, the noise appeared. I'd let it some more time under test at the tech's shop. I'd tell him to listen for some days before giving it back.

Of course it could be some external interference, (specially if both channels do the same noise at the same time) but if it's a noisy transistor, in some cases it can work fine for weeks before showing the noises again. From my experience, in cold weather it fails more often, and in summer or hot environment, it can be silent for longer. I've seen an amp working fine all the summer and start to make noises after a very cold night.

Per @elnaldo , the tech said he'd run the Nak for five days straight while his assistant worked on other parts during the week. Turned on at 9am, kept on until then. No pop! I asked him to try another day before I pick up.

I was able to reproduce the problem with the Yamaha CR820, but that has developed a nasty problem of clicking in/out of protection mode, so I must discount all of its results.

Finally, in a fit of impatience, I poked around Craigslist, and spoke with a nice gentleman who offered to sell me his entire Nikko stack for almost 60% of his original asking. It includes unmolested Alpha 220 amp, Beta 20 preamp, Gamma 20 tuner, and EQ 20. Clean fronts and all sound smooth. Importantly, there is so far no pop with the Nikko gear set up.

 

[avantbored]

The Nak has been reinstalled and the pop has returned. Maybe Ive worn out that outlet or the circuit?

 

[elnaldo]

You stated that the noise was not present with the Nikko gear, but returned with the NAK device. If the noise is present only when using the Nak PA7II, I'd still suspect the amplifier. If you had the same noise with other amps in the same setup, it could be some other device causing it.

If i'm not missing something in your descriptions, you never reported the same noises present with other amps. You mentioned the NAK PA7II not doing noises for some time, but noises returned always with that same amp.

From here, to me, it sounds like the amp has an intermittent problem, something usual to us who repair amplifiers.

Please , in case I didn't see it before in the thread, let us know if you had those noises using other amplifier.

 

[Mr.White]

I get pops from my living room tube receiver if newer light bulbs are installed in my kitchen. It happens when the lights are turned on. I now use older incandescent light bulbs, no pops.