Help eliminating what is causing a speaker pop with a Fostex HP-A4BL DAC
May 10, 2021 at 9:41 AM Thread Starter Post #1 of 5

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Hi everyone,

This is my last ditch attempt to get some advice on using the USB functionality of this DAC before I just decide to give in and use optical.

A short chain kicked off in the dedicated topic looking for help but given low traffic in there I'd like to open up to all of you https://www.head-fi.org/threads/fostex-hp-a4bl-the-a4-with-balanced-output.792916/post-16330636

The tldr is I have a piercing pop noise coming out of one of my speakers when using USB most noticeable when sound is first sent to the speakers/power on, but reproducible if I have no audio playing and then start something up like a YouTube video. When the audio is playing there is no issues, but if I use the seek bar on YouTube, that brief gap of silence before audio starts again produces that piercing pop. If I swap the phono outputs on the back of the Fostex to reverse R/L, the pop goes to the other speaker.

From the topic above I've tried a USB powered hub, a laptop on battery, another USB cable with ferrites (instead of Fostex default), 2 sets of powered speakers, an AV loop isolator and just today Fostex sent me a grounded power supply. Nothing has helped. The AV isolator loop actually INTRODUCED hum/buzz, neither of which I have at the moment lol, just the pop. Though it was a cheaper Amazon phono AV loop isolator (quality might be an issue here). Optical works absolutely fine, with either set of speakers.

The only common denominator between my laptop and PC is Windows 10. I have also tried to get audio playing through a Galaxy S20, but for whatever reason whilst my S20 seems to pickup the Fostex, I can't get it passing any audio over USB.

Has anyone had an issue like this? (I'll try record noise later for you). I do know the easy answer is use optical, just forget USB. But it's hard to give up troubleshooting :dt880smile: I know there are more expensive USB isolators that I guess might produce a result than an external powered USB hub. £50 a pop though for one of those iFi iSilencer dongles and a lot of people seem to use them for hum/buzz, neither of which I think I have. Mines is more like a sharp pop, it's not constant.

Cheers
 
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May 10, 2021 at 4:41 PM Post #2 of 5
Try:
1.) A USB 2.0 port instead of USB 3.0
2.) Turn off Power Management on the Universal Serial Bus Controllers in Device Manager.
( Mainly the USB HUB devices
3.) Sometimes it is caused by the DAC not muting the output during sample rate changes.
4.) Make sure your BIOS is up to date as there may be power issues with your motherboard not addressed on an older BIOS
5.) Is your RAM RGB? RGB RAM introduces noise into the audio chain
6.) Install the exact driver for the DAC and don't let Windows use it's own driver.
7.) Some of these issues arise from DPC latency.

Here is some general guidance on what I would check after those fixes.

https://www.howtogeek.com/285429/ho...part of Windows that handles hardware drivers.
 
May 10, 2021 at 4:50 PM Post #3 of 5
Try:
1.) A USB 2.0 port instead of USB 3.0
2.) Turn off Power Management on the Universal Serial Bus Controllers in Device Manager.
( Mainly the USB HUB devices
3.) Sometimes it is caused by the DAC not muting the output during sample rate changes.
4.) Make sure your BIOS is up to date as there may be power issues with your motherboard not addressed on an older BIOS
5.) Is your RAM RGB? RGB RAM introduces noise into the audio chain
6.) Install the exact driver for the DAC and don't let Windows use it's own driver.
7.) Some of these issues arise from DPC latency.

Here is some general guidance on what I would check after those fixes.

https://www.howtogeek.com/285429/how-to-fix-crackling-or-popping-sound-on-a-windows-pc/#:~:text=1 Change Your Audio Format. Changing the audio,the part of Windows that handles hardware drivers.

Hi, thanks for the detailed list of things to try.

Your first point is a good one as the Fostex is a USB 2.0 port and cable. Unfortunately just about everything I have is USB 3.0 lol. Even the powered hub I bought is USB 3.0. I will try to see if I can get ahold of a USB 2.0 hub.

My PC is quite cutting edge, Ryzen 3900XT, 32GB RGB Vengeance Pro, X570 Asus mobo (BIOS up to date). I would start looking at the RAM if it weren't for the fact I can reproduce the issue on my Surface Book 2 laptop. It is USB 3.0 as well. It runs intel. Only thing similar between the PC and laptop is USB 3.0 and Windows 10.

DAC is using the latest Fostex driver from here https://fostexinternational.com/docs/products/HP-A4BL.shtml

I will see if I can get a USB 2.0 source and I'll also look at that howtogeek link. From the Fostex official topic on this forum it appears quite a few people use USB 3.0, but it's still something worth looking into.

Latency of RAM I belive is naturally a bit higher on the AMD Ryzen platform than it is on Intel, but AMD chips have been really popular for quite a few years now. Given my laptop being on intel, it gives me both main hardware providers to test.

Point 3 sounds like an interesting theory, but then would that be hardware??? Wouldn't this also happen on optical or is it just handled completely differently?

SDXe7E3.png


Latency seems possibly dodgy, but it took a while for that conclusion to change from "OK".

I guess I'll try turning all the AMD powersaving functions off lol.

_________________________________________________________________________________________________________
CONCLUSION
_________________________________________________________________________________________________________
Your system seems to be having difficulty handling real-time audio and other tasks. You may experience drop outs, clicks or pops due to buffer underruns. One or more DPC routines that belong to a driver running in your system appear to be executing for too long. One problem may be related to power management, disable CPU throttling settings in Control Panel and BIOS setup. Check for BIOS updates.
LatencyMon has been analyzing your system for 0:15:55 (h:mm:ss) on all processors.


_________________________________________________________________________________________________________
SYSTEM INFORMATION
_________________________________________________________________________________________________________
Computer name: DESKTOP-81RQDCP
OS version: Windows 10, 10.0, version 2009, build: 19042 (x64)
Hardware: System Product Name, System manufacturer
CPU: AuthenticAMD AMD Ryzen 9 3900XT 12-Core Processor
Logical processors: 24
Processor groups: 1
RAM: 32677 MB total


_________________________________________________________________________________________________________
CPU SPEED
_________________________________________________________________________________________________________
Reported CPU speed: 380 MHz

Note: reported execution times may be calculated based on a fixed reported CPU speed. Disable variable speed settings like Intel Speed Step and AMD Cool N Quiet in the BIOS setup for more accurate results.


_________________________________________________________________________________________________________
MEASURED INTERRUPT TO USER PROCESS LATENCIES
_________________________________________________________________________________________________________
The interrupt to process latency reflects the measured interval that a usermode process needed to respond to a hardware request from the moment the interrupt service routine started execution. This includes the scheduling and execution of a DPC routine, the signaling of an event and the waking up of a usermode thread from an idle wait state in response to that event.

Highest measured interrupt to process latency (µs): 337.30
Average measured interrupt to process latency (µs): 5.284961

Highest measured interrupt to DPC latency (µs): 333.70
Average measured interrupt to DPC latency (µs): 1.177812


_________________________________________________________________________________________________________
REPORTED ISRs
_________________________________________________________________________________________________________
Interrupt service routines are routines installed by the OS and device drivers that execute in response to a hardware interrupt signal.

Highest ISR routine execution time (µs): 14.310
Driver with highest ISR routine execution time: Wdf01000.sys - Kernel Mode Driver Framework Runtime, Microsoft Corporation

Highest reported total ISR routine time (%): 0.000087
Driver with highest ISR total time: Wdf01000.sys - Kernel Mode Driver Framework Runtime, Microsoft Corporation

Total time spent in ISRs (%) 0.000087

ISR count (execution time <250 µs): 33751
ISR count (execution time 250-500 µs): 0
ISR count (execution time 500-1000 µs): 0
ISR count (execution time 1000-2000 µs): 0
ISR count (execution time 2000-4000 µs): 0
ISR count (execution time >=4000 µs): 0


_________________________________________________________________________________________________________
REPORTED DPCs
_________________________________________________________________________________________________________
DPC routines are part of the interrupt servicing dispatch mechanism and disable the possibility for a process to utilize the CPU while it is interrupted until the DPC has finished execution.

Highest DPC routine execution time (µs): 1173.850
Driver with highest DPC routine execution time: nvlddmkm.sys - NVIDIA Windows Kernel Mode Driver, Version 466.27 , NVIDIA Corporation

Highest reported total DPC routine time (%): 0.004795
Driver with highest DPC total execution time: nvlddmkm.sys - NVIDIA Windows Kernel Mode Driver, Version 466.27 , NVIDIA Corporation

Total time spent in DPCs (%) 0.014205

DPC count (execution time <250 µs): 606853
DPC count (execution time 250-500 µs): 0
DPC count (execution time 500-10000 µs): 18
DPC count (execution time 1000-2000 µs): 1
DPC count (execution time 2000-4000 µs): 0
DPC count (execution time >=4000 µs): 0


_________________________________________________________________________________________________________
REPORTED HARD PAGEFAULTS
_________________________________________________________________________________________________________
Hard pagefaults are events that get triggered by making use of virtual memory that is not resident in RAM but backed by a memory mapped file on disk. The process of resolving the hard pagefault requires reading in the memory from disk while the process is interrupted and blocked from execution.

NOTE: some processes were hit by hard pagefaults. If these were programs producing audio, they are likely to interrupt the audio stream resulting in dropouts, clicks and pops. Check the Processes tab to see which programs were hit.

Process with highest pagefault count: firefox.exe

Total number of hard pagefaults 7092
Hard pagefault count of hardest hit process: 2746
Number of processes hit: 30


_________________________________________________________________________________________________________
PER CPU DATA
_________________________________________________________________________________________________________
CPU 0 Interrupt cycle time (s): 2.929929
CPU 0 ISR highest execution time (µs): 1.90
CPU 0 ISR total execution time (s): 0.000147
CPU 0 ISR count: 195
CPU 0 DPC highest execution time (µs): 60.680
CPU 0 DPC total execution time (s): 0.047392
CPU 0 DPC count: 38481
_________________________________________________________________________________________________________
CPU 1 Interrupt cycle time (s): 1.858576
CPU 1 ISR highest execution time (µs): 1.590
CPU 1 ISR total execution time (s): 0.000030
CPU 1 ISR count: 43
CPU 1 DPC highest execution time (µs): 232.250
CPU 1 DPC total execution time (s): 0.002180
CPU 1 DPC count: 904
_________________________________________________________________________________________________________
CPU 2 Interrupt cycle time (s): 2.717499
CPU 2 ISR highest execution time (µs): 7.360
CPU 2 ISR total execution time (s): 0.000279
CPU 2 ISR count: 392
CPU 2 DPC highest execution time (µs): 161.070
CPU 2 DPC total execution time (s): 0.051919
CPU 2 DPC count: 31771
_________________________________________________________________________________________________________
CPU 3 Interrupt cycle time (s): 2.429920
CPU 3 ISR highest execution time (µs): 3.230
CPU 3 ISR total execution time (s): 0.000470
CPU 3 ISR count: 794
CPU 3 DPC highest execution time (µs): 48.180
CPU 3 DPC total execution time (s): 0.009484
CPU 3 DPC count: 2087
_________________________________________________________________________________________________________
CPU 4 Interrupt cycle time (s): 3.402326
CPU 4 ISR highest execution time (µs): 5.870
CPU 4 ISR total execution time (s): 0.002482
CPU 4 ISR count: 5960
CPU 4 DPC highest execution time (µs): 120.860
CPU 4 DPC total execution time (s): 0.079790
CPU 4 DPC count: 20192
_________________________________________________________________________________________________________
CPU 5 Interrupt cycle time (s): 2.034391
CPU 5 ISR highest execution time (µs): 1.630
CPU 5 ISR total execution time (s): 0.000129
CPU 5 ISR count: 244
CPU 5 DPC highest execution time (µs): 38.190
CPU 5 DPC total execution time (s): 0.005714
CPU 5 DPC count: 2010
_________________________________________________________________________________________________________
CPU 6 Interrupt cycle time (s): 4.352623
CPU 6 ISR highest execution time (µs): 13.220
CPU 6 ISR total execution time (s): 0.002327
CPU 6 ISR count: 3333
CPU 6 DPC highest execution time (µs): 173.040
CPU 6 DPC total execution time (s): 0.191310
CPU 6 DPC count: 72845
_________________________________________________________________________________________________________
CPU 7 Interrupt cycle time (s): 3.614942
CPU 7 ISR highest execution time (µs): 14.310
CPU 7 ISR total execution time (s): 0.007297
CPU 7 ISR count: 15019
CPU 7 DPC highest execution time (µs): 170.220
CPU 7 DPC total execution time (s): 0.221562
CPU 7 DPC count: 44029
_________________________________________________________________________________________________________
CPU 8 Interrupt cycle time (s): 2.574857
CPU 8 ISR highest execution time (µs): 2.470
CPU 8 ISR total execution time (s): 0.000902
CPU 8 ISR count: 845
CPU 8 DPC highest execution time (µs): 87.740
CPU 8 DPC total execution time (s): 0.078540
CPU 8 DPC count: 25448
_________________________________________________________________________________________________________
CPU 9 Interrupt cycle time (s): 1.938114
CPU 9 ISR highest execution time (µs): 1.950
CPU 9 ISR total execution time (s): 0.000054
CPU 9 ISR count: 54
CPU 9 DPC highest execution time (µs): 63.160
CPU 9 DPC total execution time (s): 0.027146
CPU 9 DPC count: 6415
_________________________________________________________________________________________________________
CPU 10 Interrupt cycle time (s): 2.173985
CPU 10 ISR highest execution time (µs): 2.070
CPU 10 ISR total execution time (s): 0.000043
CPU 10 ISR count: 34
CPU 10 DPC highest execution time (µs): 173.930
CPU 10 DPC total execution time (s): 0.006422
CPU 10 DPC count: 2204
_________________________________________________________________________________________________________
CPU 11 Interrupt cycle time (s): 2.082841
CPU 11 ISR highest execution time (µs): 2.360
CPU 11 ISR total execution time (s): 0.000052
CPU 11 ISR count: 39
CPU 11 DPC highest execution time (µs): 30.760
CPU 11 DPC total execution time (s): 0.002568
CPU 11 DPC count: 595
_________________________________________________________________________________________________________
CPU 12 Interrupt cycle time (s): 2.028646
CPU 12 ISR highest execution time (µs): 1.860
CPU 12 ISR total execution time (s): 0.000019
CPU 12 ISR count: 16
CPU 12 DPC highest execution time (µs): 49.630
CPU 12 DPC total execution time (s): 0.004002
CPU 12 DPC count: 1274
_________________________________________________________________________________________________________
CPU 13 Interrupt cycle time (s): 2.094248
CPU 13 ISR highest execution time (µs): 1.610
CPU 13 ISR total execution time (s): 0.000014
CPU 13 ISR count: 15
CPU 13 DPC highest execution time (µs): 40.560
CPU 13 DPC total execution time (s): 0.004002
CPU 13 DPC count: 1315
_________________________________________________________________________________________________________
CPU 14 Interrupt cycle time (s): 2.738706
CPU 14 ISR highest execution time (µs): 2.410
CPU 14 ISR total execution time (s): 0.000091
CPU 14 ISR count: 75
CPU 14 DPC highest execution time (µs): 63.390
CPU 14 DPC total execution time (s): 0.010650
CPU 14 DPC count: 3250
_________________________________________________________________________________________________________
CPU 15 Interrupt cycle time (s): 2.397873
CPU 15 ISR highest execution time (µs): 2.190
CPU 15 ISR total execution time (s): 0.000117
CPU 15 ISR count: 117
CPU 15 DPC highest execution time (µs): 48.680
CPU 15 DPC total execution time (s): 0.007056
CPU 15 DPC count: 2956
_________________________________________________________________________________________________________
CPU 16 Interrupt cycle time (s): 13.758988
CPU 16 ISR highest execution time (µs): 2.310
CPU 16 ISR total execution time (s): 0.000697
CPU 16 ISR count: 878
CPU 16 DPC highest execution time (µs): 891.320
CPU 16 DPC total execution time (s): 0.385957
CPU 16 DPC count: 59110
_________________________________________________________________________________________________________
CPU 17 Interrupt cycle time (s): 3.952397
CPU 17 ISR highest execution time (µs): 1.960
CPU 17 ISR total execution time (s): 0.000033
CPU 17 ISR count: 41
CPU 17 DPC highest execution time (µs): 285.420
CPU 17 DPC total execution time (s): 0.021671
CPU 17 DPC count: 3008
_________________________________________________________________________________________________________
CPU 18 Interrupt cycle time (s): 10.944706
CPU 18 ISR highest execution time (µs): 7.190
CPU 18 ISR total execution time (s): 0.000727
CPU 18 ISR count: 789
CPU 18 DPC highest execution time (µs): 500.620
CPU 18 DPC total execution time (s): 0.490628
CPU 18 DPC count: 68781
_________________________________________________________________________________________________________
CPU 19 Interrupt cycle time (s): 20.028493
CPU 19 ISR highest execution time (µs): 2.780
CPU 19 ISR total execution time (s): 0.002711
CPU 19 ISR count: 3379
CPU 19 DPC highest execution time (µs): 1173.850
CPU 19 DPC total execution time (s): 1.568534
CPU 19 DPC count: 211570
_________________________________________________________________________________________________________
CPU 20 Interrupt cycle time (s): 3.220457
CPU 20 ISR highest execution time (µs): 2.380
CPU 20 ISR total execution time (s): 0.000916
CPU 20 ISR count: 1044
CPU 20 DPC highest execution time (µs): 78.850
CPU 20 DPC total execution time (s): 0.022089
CPU 20 DPC count: 5510
_________________________________________________________________________________________________________
CPU 21 Interrupt cycle time (s): 2.491291
CPU 21 ISR highest execution time (µs): 1.920
CPU 21 ISR total execution time (s): 0.000043
CPU 21 ISR count: 45
CPU 21 DPC highest execution time (µs): 38.570
CPU 21 DPC total execution time (s): 0.002504
CPU 21 DPC count: 528
_________________________________________________________________________________________________________
CPU 22 Interrupt cycle time (s): 2.738256
CPU 22 ISR highest execution time (µs): 5.670
CPU 22 ISR total execution time (s): 0.000282
CPU 22 ISR count: 297
CPU 22 DPC highest execution time (µs): 57.830
CPU 22 DPC total execution time (s): 0.009901
CPU 22 DPC count: 1772
_________________________________________________________________________________________________________
CPU 23 Interrupt cycle time (s): 2.641439
CPU 23 ISR highest execution time (µs): 2.920
CPU 23 ISR total execution time (s): 0.000119
CPU 23 ISR count: 103
CPU 23 DPC highest execution time (µs): 52.210
CPU 23 DPC total execution time (s): 0.004807
CPU 23 DPC count: 817
_________________________________________________________________________________________________________
 
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May 10, 2021 at 6:16 PM Post #4 of 5
Sorry for bumping my own topic but I've just discovered something else playing around with connections. With both USB and optical cables disconnected from the HPA4BL, I can get the pop repeating by simply toggling between USB/optical with the front switch on the HPA4BL.

Secondly, I might have mentioned about switching the phono outputs to make the pop come out the right speaker instead of left. Well, if I disconnect the left phono output on the back of the HPA4BL unit it doesn't matter if I plug right or left cable into the right phono, there is no popping when switching between USB/optical.

I'm beginning to think I have a faulty left phono output connection on the back of the Fostex HPA4BL. The speaker pop is still there with absolutely no devices plugged in and the pop is only coming from the left output, not the right. Or is this purely a "power" related thing because the DAC is switching the input its accepting which causes the speakers to pop once even if there is no input connected? Why though would that only affect the left phono output on the back of the unit?
 
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