3e audio A7/A7 Mono Amplifier Review

[Roland68]

There would be no way to test whether any pop occurs with just the amp plugged in, and nothing else connected because you've removed the ability to play any audio through the amplifier. This is not a case of random pops happening while the amp is sitting idle, which is why it is not a grounding issue.

The pops occur when audio is paused (i.e. when playing music from my Mac's Music app -- it probably also occurs if I were to trigger a system notification sound, or paused a YouTube video). And it's two pops, about 0.5 to 1s after the audio has stopped -- consistently, every time. I also want to stress, again, that this does not happen with any other power amplifier I've used in the same system with the same cables, same connection chain, etc...

Edit: I've attached a link to an audio file to demonstrate the issue... please let me know if there are any issues accessing the file.

New-Recording.mp3

drive.google.com

At 3 seconds, you will hear the first mouse click starting the audio, at 16 seconds, you will hear the second mouse click pausing the audio, and shortly after you will hear two pops.

Edit 2:

So I have gone through a variety of different tests, and this was the results:

- I disabled auto sensing on the A7: same results (two pops after pausing)
- I then connected the A7 directly to a different DAC -- the Topping E50 -- via TRS: same results
- I then connected the A7 to the E50 with different balanced cables (TRS to XLR), slightly different results: One audible pop after pausing sitting 2 feet away (I did not listen with my ears any closer, but I bet there was a second pop that wasn't as audible)
- I then connected the A7 to the E50 via RCA: no audible pops sitting 2 feet away**
- I then reconnected the A7 to the regular chain (D50 III to L50 HPA to A7, all via TRS), and changed the output level on the D50 III from 5v to 4v: same results (two pops after pausing)
- I then connected the A7 directly to the D50 III DAC via RCA: no audible pops sitting two feet away**

** no audible pops when 2 feet away, but there was the faintest of ticks when I had my ear within 3 inches of the speakers. And honestly, if that was the result with the balanced connection, I wouldn't actually care because the tick with the RCA connection is so minuscule that sitting at my normal distance, it wouldn't have even been noticed.

I performed all of the same tests above with my Topping PA5 II amplifier, and there wasn't the slightest pop, tick, etc...

Sadly, based on all of this, I must come to the conclusion that the A7 amplifier needs to be returned. Another thing I discovered is that when connected via RCA, the RCA gain switch on the back of the amplifier does absolutely nothing. There is no change in the gain level switching from L to H (Low to High). I don't know if it's defective, or if that's normal functionality?

I would still like to hear a response feedback from @3eaudio on this.

That sounds like a grounding problem, unfortunately an extremely complex one.

If you've turned off automatic detection, the popping can't actually be coming directly from the A7 anymore, but is just being amplified by it.

What's your source, and how is it connected to the DAC?

Could you try connecting via Bluetooth with one of the DACs?

 

[ziggurcat]

That sounds like a grounding problem, unfortunately an extremely complex one.

If you've turned off automatic detection, the popping can't actually be coming directly from the A7 anymore, but is just being amplified by it.

What's your source, and how is it connected to the DAC?

Could you try connecting via Bluetooth with one of the DACs?

What is it about the A7 that would cause it to be the only component in the system to exhibit that behaviour? Bearing in mind, again, that none of this is a thing when any other speaker amplifier is used.

What does the change in behaviour with the RCA connection indicate to you?

Sorry, I thought I had mentioned the source in an earlier post, but apparently not... Source was the same throughout, and has been the same for a few years: my Mac Mini M1 (2020). Currently, the DAC is connected via USB-C -- which is its only USB connector type -- to the Mac. I am using one of the main thunderbolt outputs. When I tested with the E50, I used the USB-A output from the Mac to the DAC's USB-B input.

Thank you, I did not think about using BT. It is far too late right now to be doing any of this, so that will be tested when I get home from work tomorrow afternoon. I can also re-test TRS to XLR again to confirm whether there is only the one pop with that connection. I cannot test BT with the E50 DAC since it does not have that type of connection, but the D50 III does.

Another test I can conduct is (because results were the same with both DACs) bring my E50, and the A7 over to the bedroom, and connect it to my TV in there (for kicks, I'll also test with the D50 III). Different source, likely different power circuit -- in that test, I would be connecting to the DAC with TOSLINK from the TV (so different connection type from the source to the DAC), then TRS out to the A7 (I will also try TRS to XLR). That might have to wait until Sunday, though.

 

[Roland68]

What is it about the A7 that would cause it to be the only component in the system to exhibit that behaviour? Bearing in mind, again, that none of this is a thing when any other speaker amplifier is used.

What does the change in behaviour with the RCA connection indicate to you?

Sorry, I thought I had mentioned the source in an earlier post, but apparently not... Source was the same throughout, and has been the same for a few years: my Mac Mini M1 (2020). Currently, the DAC is connected via USB-C -- which is its only USB connector type -- to the Mac. I am using one of the main thunderbolt outputs. When I tested with the E50, I used the USB-A output from the Mac to the DAC's USB-B input.

Thank you, I did not think about using BT. It is far too late right now to be doing any of this, so that will be tested when I get home from work tomorrow afternoon. I can also re-test TRS to XLR again to confirm whether there is only the one pop with that connection. I cannot test BT with the E50 DAC since it does not have that type of connection, but the D50 III does.

Another test I can conduct is (because results were the same with both DACs) bring my E50, and the A7 over to the bedroom, and connect it to my TV in there (for kicks, I'll also test with the D50 III). Different source, likely different power circuit -- in that test, I would be connecting to the DAC with TOSLINK from the TV (so different connection type from the source to the DAC), then TRS out to the A7 (I will also try TRS to XLR). That might have to wait until Sunday, though.

As I said, this topic is extremely complex and has several dependencies.
Where you connect the device on your Mac is absolutely irrelevant, since each of your DACs only has USB 2.0, which the Mac must also use.

Ideally, a test would be with a source connected via Bluetooth or Toslink, and no power connection for the DAC comes from the Mac.

 

[Chaos01]

As I said, this topic is extremely complex and has several dependencies.
Where you connect the device on your Mac is absolutely irrelevant, since each of your DACs only has USB 2.0, which the Mac must also use.

Ideally, a test would be with a source connected via Bluetooth or Toslink, and no power connection for the DAC comes from the Mac.

The question is If he dont have the issue with other amps why keep this one? Why dont they have the issue or can handle the ground Problem or why the A7 have/create a ground problem? And the high gain Switch should lift Up the Volume at Same Level, right? So my guess is there is something wrong in the unit, maybe in assembling. As Long Nobody Here can recreate the issue, i would send it Back and try a new one, that would have save you many time.
Greetings

 

[harkpabst]

The question is If he dont have the issue with other amps why keep this one? Why dont they have the issue or can handle the ground Problem or why the A7 have/create a ground problem? And the high gain Switch should lift Up the Volume at Same Level, right? So my guess is there is something wrong in the unit, maybe in assembling. As Long Nobody Here can recreate the issue, i would send it Back and try a new one, that would have save you many time.
Greetings

The high gain switch affects the RCA inputs only.

And if I remember correctly, the RCA inputs are not affected anyway.

Is the PA5II fully differential internally?

 

[ziggurcat]

As I said, this topic is extremely complex and has several dependencies.
Where you connect the device on your Mac is absolutely irrelevant, since each of your DACs only has USB 2.0, which the Mac must also use.

Ideally, a test would be with a source connected via Bluetooth or Toslink, and no power connection for the DAC comes from the Mac.

Using a different USB out from the Mac was only to eliminate the one that was being used by the D50 II as the culprit.

As I mentioned, I will test the BT connection (I will try streaming from the Mac itself, and also from my phone), and let you know the results. There will be no physical connection from the Mac to the DAC in that test. I won't test with RCA connection out from the DAC because I already know that with RCA there's nothing particularly wrong. In that scenario, if I have to put my ear right up to the speaker in order to hear the faintest of pops (and I had to really focus my attention), then that is a non-issue for me. The problem is only, truly evident when some kind of balanced connection is used from DAC to A7 (regardless of whether my L50 HPA is in the chain).

If the BT test yields the same popping issue, what do you theorize could be the issue?

 

[Roland68]

The question is If he dont have the issue with other amps why keep this one? Why dont they have the issue or can handle the ground Problem or why the A7 have/create a ground problem? And the high gain Switch should lift Up the Volume at Same Level, right? So my guess is there is something wrong in the unit, maybe in assembling. As Long Nobody Here can recreate the issue, i would send it Back and try a new one, that would have save you many time.
Greetings

Some of your questions are certainly directed at the A7 owner, so I'm the wrong person to ask.
But your questions show that you don't even begin to understand the complexity of this issue.
You can assume that most systems have a grounding problem, and there are various types. However, most are inaudible, or not clearly audible. Especially with USB and the many devices without a ground connection, the problems occur much more frequently; the cause is difficult to determine and is often caused by the combination of different devices and connections.

Of course, the A7 could be defective, but it also might not be.
And it would be an absolutely stupid idea not to run certain tests now and isolate the problem, because the problem could also occur with another amplifier.
Because if you think about it a little more closely, the A7 is switched on, and the bang is triggered by starting and stopping the music. The A7 only amplifies the incoming signal, so there is a very high probability that the popping noise is already contained in the incoming signal.

 

[ziggurcat]

The question is If he dont have the issue with other amps why keep this one? Why dont they have the issue or can handle the ground Problem or why the A7 have/create a ground problem? And the high gain Switch should lift Up the Volume at Same Level, right? So my guess is there is something wrong in the unit, maybe in assembling. As Long Nobody Here can recreate the issue, i would send it Back and try a new one, that would have save you many time.
Greetings

That is what I am struggling to understand -- why is this not a problem with any other amplifier when it is from the same source in the same system, using the same TRS connection chain. I am willing to do the tests because that is the proper thing to do in order to rule out the A7 (it's only fair), but I am not 100% convinced at this time that is a grounding problem, but I am not going to completely cross it off the list entirely until it is 100% certain.

Since I don't think there has been anyone else describing this problem, and with what I discovered when RCA was used to connect my DACs to the A7, either everyone else is using RCA or my specific unit has an issue. I would love to find out if anyone with a current production unit (not the pre-production unit) has noticed this issue, and if they're using RCA, they can possibly test the balanced inputs on their units.

The high gain switch affects the RCA inputs only.

And if I remember correctly, the RCA inputs are not affected anyway.

Is the PA5II fully differential internally?

I can say that when I used the RCA connection, flipping the RCA Gain switch on the back of the A7 didn't have any audible impact (I even had audio playing as I flipped the switch back and forth), so I am not entirely sure what it does.

 

[ziggurcat]

because the problem could also occur with another amplifier.

The A7 is the only amplifier, so far, that has exhibited this behaviour. The issue has not been observed with both the Topping PA5 II and Topping PA3s amplifiers (I introduced the PA3s and PA5 II into the system over the last 1.5 years).

In this same system (i.e. the same Mac Mini source in the same room on the same outlet), I have also used a Cambridge Audio AXR100 (what I started with), and a Topping MX5 -- both of which have not exhibited any popping after audio has been paused/stopped. I would say that between when the AXR100 was being used to the current setup, it is about a 2 to 3-year span of time.

My recollection of when I was using the AXR100 is that the connection chain was: Mac Mini -- USB --> Topping D10s DAC -- RCA --> AXR100. The Topping MX5 would have been connected via USB from the Mac to the MX5.

Edit:

@Roland68 one other connection option I can try is to connect my Mac Mini directly to the A7 using the headphone output with a 3.5mm to RCA cable. I suspect it would yield the same result as the tests with an RCA connection I did yesterday, but I think it's still worth trying.

 

[Nyarlathotep]

The A7 is the only amplifier, so far, that has exhibited this behaviour. The issue has not been observed with both the Topping PA5 II and Topping PA3s amplifiers (I introduced the PA3s and PA5 II into the system over the last 1.5 years).

In this same system (i.e. the same Mac Mini source in the same room on the same outlet), I have also used a Cambridge Audio AXR100 (what I started with), and a Topping MX5 -- both of which have not exhibited any popping after audio has been paused/stopped. I would say that between when the AXR100 was being used to the current setup, it is about a 2 to 3-year span of time.

My recollection of when I was using the AXR100 is that the connection chain was: Mac Mini -- USB --> Topping D10s DAC -- RCA --> AXR100. The Topping MX5 would have been connected via USB from the Mac to the MX5.

Edit:

@Roland68 one other connection option I can try is to connect my Mac Mini directly to the A7 using the headphone output with a 3.5mm to RCA cable. I suspect it would yield the same result as the tests with an RCA connection I did yesterday, but I think it's still worth trying.

That does not necessarily definitively mean the A7 is defective or has a design flaw, nor does it mean that some future device chain configuration won't suffer the same manifestation. The point posters are trying to make clear is there could be a grounding issue somewhere else in the chain, not caused by the A7, and to no fault of the A7s design, that some other (not all) amps may also be be impacted by. Others amps could similarly be affected in the future due to this potential, unresolved grounding issue.

In other words, grounding can be complicated, and while swapping in/out the A7 is good troubleshooting, it only indicates the A7 is sensitive to this grounding situation, but the cause of the issue may or may not be a due to some other interconnections within your setup and may still occur with other components swapped around.

 

[Roland68]

The A7 is the only amplifier, so far, that has exhibited this behaviour. The issue has not been observed with both the Topping PA5 II and Topping PA3s amplifiers (I introduced the PA3s and PA5 II into the system over the last 1.5 years).

In this same system (i.e. the same Mac Mini source in the same room on the same outlet), I have also used a Cambridge Audio AXR100 (what I started with), and a Topping MX5 -- both of which have not exhibited any popping after audio has been paused/stopped. I would say that between when the AXR100 was being used to the current setup, it is about a 2 to 3-year span of time.

My recollection of when I was using the AXR100 is that the connection chain was: Mac Mini -- USB --> Topping D10s DAC -- RCA --> AXR100. The Topping MX5 would have been connected via USB from the Mac to the MX5.

Edit:

@Roland68 one other connection option I can try is to connect my Mac Mini directly to the A7 using the headphone output with a 3.5mm to RCA cable. I suspect it would yield the same result as the tests with an RCA connection I did yesterday, but I think it's still worth trying.

The most sensible test would actually be to feed the DAC with Toslink and with a power supply independent of the PC or Mac.

 

[ziggurcat]

That does not necessarily definitively mean the A7 is defective or has a design flaw, nor does it mean that some future device chain configuration won't suffer the same manifestation. The point posters are trying to make clear is there could be a grounding issue somewhere else in the chain, not caused by the A7, and to no fault of the A7s design, that some other (not all) amps may also be be impacted by. Others amps could similarly be affected in the future due to this potential, unresolved grounding issue.

In other words, grounding can be complicated, and while swapping in/out the A7 is good troubleshooting, it only indicates the A7 is sensitive to this grounding situation, but the cause of the issue may or may not be a due to some other interconnections within your setup and may still occur with other components swapped around.

For sure, which is why I was careful to say in that response that so far it's the only thing, and why I am fine to conduct more tests. I'm even going to try the A7 in a completely different system in a different room to rule out my Mac, and any other device in that chain (including the outlet/surge protector).

I think it would also be useful if anyone else has a "proper" production model (by that I just mean not a pre-production model like what was used for this site's review), and uses RCA to switch to the balanced connection as a quick test. Because the problem virtually went away the moment I used the RCA output from the DAC to RCA input on the A7, which seems like it's an important clue. I don't necessarily have a problem with using an RCA connection, but I also don't think that an end user should be forced to use one connection over the other because of a potential functional issue with the device.

All of this is vaguely reminiscent of a popping issue with the SMSL RAW MDA-1 DAC/HPA I tried. That popping issue -- occurring in the same way (i.e. after pausing/stopping audio content) -- is a known issue, documented by multiple owners,. It's what had me thinking that it may have been related to the A7's auto sensing function, and not a grounding issue.

The most sensible test would actually be to feed the DAC with Toslink and with a power supply independent of the PC or Mac.

Which is what I can/will do when I try the A7 with my bedroom TV setup. I will try with no physical connection between the Mac and the rest of the devices where it is now first, though.

 

[Panelhead]

Sounds like you need a Topping to get rid of your Popping.

 

[ziggurcat]

Sounds like you need a Topping to get rid of your Popping.

The defining moment will be when I test everything in the bedroom setup.

 

[ziggurcat]

@Roland68 OK, so... I have returned home from work, and I ran the first couple of tests. These were the conditions, and the results:

- D50 III was set to DAC Mode, volume bypass on the A7 was disabled. Connected my Mac Mini to the DAC via Bluetooth (thus removing the physical connection to the Mac entirely), connected the D50 III to the A7 via TRS: No audible popping observed, even when holding my ear right up to the speakers' tweeter/woofer.

- Keeping things connected via Bluetooth, I then changed the DAC to preamp mode, enabled the A7's volume bypass with the DAC still connected to the A7 via TRS: No audible popping observed, even when my ear was right up against the speakers.

- Disconnected the DAC, and connected the Mac directly to the A7 using the Mac's 3.5mm headphone out with a 3.5mm to RCA cable. Volume bypass on the A7 was disabled, Mac's volume control was at max: No audible popping observed, even listening with my ear right up to the speakers.

- Keeping the A7 connected directly to the Mac via 3.5mm to RCA, I then enabled the A7's volume bypass: Two pops were observed, but it was faint (I had to hold my ear up to the speaker's tweeter/woofer to hear it). Using the Mac's volume control I tested at 50% volume up to 75% volume.

- I then reverted everything back to how everything was connected (Mac Mini -- USB --> D50 III -- TRS --> A7). Because I forgot to test this yesterday, I then set the D50 III to preamp mode, and enabled the A7's volume bypass: No audible popping observed, even when my ear was right up to the speaker. The highest volume setting on the DAC was set at -18dB starting from -30dB.

- Thinking that was very strange, I reverted the D50 III back to its DAC mode, and disabled the A7's volume bypass: Two pops were observed, just as it was yesterday, sitting two feet away from the speakers.

What do you make of that nonsense?

Edit:

I did double check TRS to XLR at the default connect, and I can confirm that there were two pops even though I thought I only heard one yesterday.

Again, because I think I forgot to check this yesterday, I did connect the DAC via RCA to the A7 again, and with the A7's volume bypass enabled, and the D50 III set to preamp mode, two pops were observed. Setting the D50 III to DAC mode, and disabling the A7's volume bypass, no pops were observed sitting 2 feet away (one minuscule pop was heard when my ear was up against the speaker as it was yesterday).

I did also try that RCA gain switch on the A7 again, and there was a slight increase in SPL when I flipped it to High with RCA connected. Don't know why I didn't detect that yesterday.

 

[Panelhead]

I will be serious this time. The Mac Mini USB connection is issue. For some reason not all dacs and amps reveal it.
Not sure if you are gender changing USB cables or not. I used Mini’s for long time, started with a 2009. Late 2012’s, maybe 2016. Stopped. But all were FW or TB. Never really used USB 2.0.
Some had optical. Inside the 3.5 mm connector. Used a long skinny Toslink adapter. Do not know if 2020 model has this. But this would solve problem.
Toslink today is as good as coax or USB. Does not have as high a bandwidth. But 192/24 should work for most of us.

 

[ziggurcat]

I will be serious this time. The Mac Mini USB connection is issue. For some reason not all dacs and amps reveal it.
Not sure if you are gender changing USB cables or not. I used Mini’s for long time, started with a 2009. Late 2012’s, maybe 2016. Stopped. But all were FW or TB. Never really used USB 2.0.
Some had optical. Inside the 3.5 mm connector. Used a long skinny Toslink adapter. Do not know if 2020 model has this. But this would solve problem.
Toslink today is as good as coax or USB. Does not have as high a bandwidth. But 192/24 should work for most of us.

My understanding was that they ditched the toslink via headphone out a while ago. I do have a mini toslink to toslink cable, and when I tried that (just before responding to you here), it did not work.

At any rate, I'm done testing for the day. I feel like I got a few answers out of it, though. Still don't know if I will return the amp because if I can't use it how I would like to have things connected (which I don't think is anything outside of normal) then I don't think it's unreasonable to send it back. While it seems the USB connection has an issue, I did hear pops going from 3.5mm to RCA with the A7's volume bypass enabled (effectively using the Mac Mini as a preamp, and controlling the volume from there), so it's not just the USB. It could be something to do with the A7's gain stage, but it doesn't necessarily mean it's defective, it seems to me that it's a little more sensitive than the other amps I've used.

I will still conduct the final test by seeing how it would function under different setup conditions (i.e. my bedroom TV setup). If it works perfectly fine in that scenario, then I may just keep it for that purpose, but I really wanted to use it for my computer system.

 

[Roland68]

@Roland68 OK, so... I have returned home from work, and I ran the first couple of tests. These were the conditions, and the results:

- D50 III was set to DAC Mode, volume bypass on the A7 was disabled. Connected my Mac Mini to the DAC via Bluetooth (thus removing the physical connection to the Mac entirely), connected the D50 III to the A7 via TRS: No audible popping observed, even when holding my ear right up to the speakers' tweeter/woofer.

- Keeping things connected via Bluetooth, I then changed the DAC to preamp mode, enabled the A7's volume bypass with the DAC still connected to the A7 via TRS: No audible popping observed, even when my ear was right up against the speakers.

- Disconnected the DAC, and connected the Mac directly to the A7 using the Mac's 3.5mm headphone out with a 3.5mm to RCA cable. Volume bypass on the A7 was disabled, Mac's volume control was at max: No audible popping observed, even listening with my ear right up to the speakers.

- Keeping the A7 connected directly to the Mac via 3.5mm to RCA, I then enabled the A7's volume bypass: Two pops were observed, but it was faint (I had to hold my ear up to the speaker's tweeter/woofer to hear it). Using the Mac's volume control I tested at 50% volume up to 75% volume.

- I then reverted everything back to how everything was connected (Mac Mini -- USB --> D50 III -- TRS --> A7). Because I forgot to test this yesterday, I then set the D50 III to preamp mode, and enabled the A7's volume bypass: No audible popping observed, even when my ear was right up to the speaker. The highest volume setting on the DAC was set at -18dB starting from -30dB.

- Thinking that was very strange, I reverted the D50 III back to its DAC mode, and disabled the A7's volume bypass: Two pops were observed, just as it was yesterday, sitting two feet away from the speakers.

What do you make of that nonsense?

Edit:

I did double check TRS to XLR at the default connect, and I can confirm that there were two pops even though I thought I only heard one yesterday.

Again, because I think I forgot to check this yesterday, I did connect the DAC via RCA to the A7 again, and with the A7's volume bypass enabled, and the D50 III set to preamp mode, two pops were observed. Setting the D50 III to DAC mode, and disabling the A7's volume bypass, no pops were observed sitting 2 feet away (one minuscule pop was heard when my ear was up against the speaker as it was yesterday).

I did also try that RCA gain switch on the A7 again, and there was a slight increase in SPL when I flipped it to High with RCA connected. Don't know why I didn't detect that yesterday.

The A7 can already be ruled out as the cause, since the popping noise didn't occur with Bluetooth.

The A7 can't actually cause a popping noise when you stop and start the music. As I suspected, this popping noise is already present in the signal (probably in the signal from the Mac) and is fed into the A7. If you have an oscilloscope, or someone in your circle of friends does, it's easy to measure.

I believe the cause is a grounding problem with the Mac, regardless of whether it's via USB or the 3.5mm jack; it just manifests itself with varying degrees of intensity. Or have you installed some software related to audio that's causing the problem?
Are you using the original USB 2.0 cable, or something else?
Do you have a multimeter?

 

[ziggurcat]

The A7 can already be ruled out as the cause, since the popping noise didn't occur with Bluetooth.

The A7 can't actually cause a popping noise when you stop and start the music. As I suspected, this popping noise is already present in the signal (probably in the signal from the Mac) and is fed into the A7. If you have an oscilloscope, or someone in your circle of friends does, it's easy to measure.

I believe the cause is a grounding problem with the Mac, regardless of whether it's via USB or the 3.5mm jack; it just manifests itself with varying degrees of intensity. Or have you installed some software related to audio that's causing the problem?
Are you using the original USB 2.0 cable, or something else?
Do you have a multimeter?

In light of these new findings, would there be anything a clueless dimwit such as myself could do to mitigate this if the Mac is the component responsible?

I'm afraid I do not have an oscilloscope. Amongst my circle of friends, I am really the only one who nerds out on this stuff, there's a limit on the depth of a rabbit hole I'm willing to go down.

That makes sense. It's interesting to me that enabling the A7's volume bypass made the pops audible when there was nothing when it was the reverse (Mac volume control maxed, and using the amp's gain knob to control the volume). This is not saying it as a fault, but would the pops being audible with the A7 have something to do with the sensitivity of the A7's gain stage? That it is is just that much more sensitive than the other amps I've tried, which resulted in the issue being revealed. Would any of that be an accurate thing to say? I would also imagine that it might be a double-edged sword kind of thing -- on the one hand, it's good in certain scenarios, and not so good in others. I am also aware that there was talk in another thread about adjusting the sensitivity of the amp as it related to the auto-sensing functionality. I know there have been some adjustments made with regards to certain gain values to improve the auto-sensing's sensitivity. The reports I read were that it kicked into standby mode at higher SPL levels than were desired, which I suspect you're already aware of...

I do not have any additional software installed on the computer. No PEQ filters from the DAC or the Mac are being applied, either. Everything was being played straight through the Mac's Music app, all local files, no streaming.

I switched to a shorter-length USB-C cable (it's 12 inches) because with all of the other wires back there, I find it annoying to deal with all of the extra length that you get in a lot of the manufacturer-provided cables. During this testing period, I did switch to the stock USB-C cable that was in the D50 III box. Apologies for not mentioning that, it was part of the testing parameters I tried, but maybe felt like it was irrelevant to the grand scope. *shrugs*

I believe I do have a multimeter. I suppose this could relate to the first question I posed above? Out of respect to the thread topic, I do not want to drag the thread so far off topic by troubleshooting a completely unrelated issue. If you had a test you would like me to conduct, please do feel free to send a PM. If it's resolvable, I would like to find out, but not here .

After all of this, I find it hard to believe that this scenario would be an isolated case, regardless of the gear anyone uses in their systems.

I do want to thank you for all of your attention with this. It has been incredibly helpful. Do you think it would be to anyone's benefit to go through with testing on the bedroom setup or no? There is a PM conversation with 3e that I will need to follow up on tomorrow to make them aware of these test results. In the time between my last response, I was giving the thought of keeping the amp some thought, and I think that I will have a use for it in the bedroom if you are confident that the BT test confirms that this issue would not occur if the source starts the connection chain with Toslink (well... technically, it would be cable box -- hdmi --> TV -- tos --> DAC).

 

[howard416]

I had a popping issue with my A5 that was due to a failed op-amp module. However, it got worse over time, and was pretty easy to reproduce (basically every time it turned on). That does not sound like what you have, though.