[davehutch]

@Audioboxer I’m curious what happens if you swap the left and right outputs from your Fostex? Does the pop stay with the ‘slave’ speaker?

 

[Audioboxer]

@Audioboxer I’m curious what happens if you swap the left and right outputs from your Fostex? Does the pop stay with the ‘slave’ speaker?

Fantastic question, I had done just about everything apart from this LOL

That switches the pop to the right speaker, what I'll refer to as the active.

Got me worried this means it might be my Fostex unit that has a faulty phono output???

 

[davehutch]

Potentially, but it also could be the way your PC switches the USB audio, in addition to a grounding problem. For what it's worth, Fostex sent me the new power supply free of charge so let's see what they say.
Swapping connectors and items in the chain, as you obviously are already aware, is the best way to fault-find. If you have access to another PC that might at least rule out software and USB drivers until you hear back from Fostex. My understanding is that a properly earthed power supply would have no 'dummy' pins so the three mains plug pins would all be metal, the cable would be 3-core (all wires connected) and the IEC connector would have three holes. Is that the case with yours?

 

[davehutch]

Also, have you tried different USB outputs on your PC?

 

[Audioboxer]

Potentially, but it also could be the way your PC switches the USB audio, in addition to a grounding problem. For what it's worth, Fostex sent me the new power supply free of charge so let's see what they say.
Swapping connectors and items in the chain, as you obviously are already aware, is the best way to fault-find. If you have access to another PC that might at least rule out software and USB drivers until you hear back from Fostex. My understanding is that a properly earthed power supply would have no 'dummy' pins so the three mains plug pins would all be metal, the cable would be 3-core (all wires connected) and the IEC connector would have three holes. Is that the case with yours?

Nah it's a dummy pin plug, or that's what I think you mean with one pin being plastic. It's a Unifive UNK318-1215 12V 1.5A. It's quite like this except 3 prong https://www.unifive.com/products/category/standard/18w/un318.html There is no 'power brick' as I call them (what you showed me on the last page), it's just a plug with some ferrites along the wire.

I've tried on my laptop and still have the issue. The laptop is Windows 10 like my PC. I tried hooking up my Galaxy S20 and while the phone seems to pickup the Fostex and the Fostex responds by appearing to acknowledge it, I can't get any sound. But this might be an Android/Samsung issue and/or I just don't know how to do audio over USB to a DAC with Android. I read someone on here had an iPhone hooked up and working but unless I go borrow an iPhone off a mate or family I can't quickly check that.

Yeah here is hoping a proper earthed power-supply helps.

Also, have you tried different USB outputs on your PC?

Yeah, it's the first thing I did. I went and bought a powered USB hub as well to see if that helped after reading advice. It doesn't, but the hub is quite a decent thing to have so no issues just keeping it.

 

[davehutch]

Nah it's a dummy pin plug, or that's what I think you mean with one pin being plastic. It's a Unifive UNK318-1215 12V 1.5A. It's quite like this except 3 prong https://www.unifive.com/products/category/standard/18w/un318.html There is no 'power brick' as I call them (what you showed me on the last page), it's just a plug with some ferrites along the wire.

I've tried on my laptop and still have the issue. The laptop is Windows 10 like my PC. I tried hooking up my Galaxy S20 and while the phone seems to pickup the Fostex and the Fostex responds by appearing to acknowledge it, I can't get any sound. But this might be an Android/Samsung issue and/or I just don't know how to do audio over USB to a DAC with Android. I read someone on here had an iPhone hooked up and working but unless I go borrow an iPhone off a mate or family I can't quickly check that.

Yeah here is hoping a proper earthed power-supply helps.



Yeah, it's the first thing I did. I went and bought a powered USB hub as well to see if that helped after reading advice. It doesn't, but the hub is quite a decent thing to have so no issues just keeping it.

OK. If I think of anything else I'll write in. Fingers crossed

 

[Audioboxer]

OK. If I think of anything else I'll write in. Fingers crossed

Thanks.

One question I could throw at you is would a grounding problem not manifest itself over an optical connection? I know the answer to many pops, crackles and hums is "just use optical", but I don't know the science behind why that works

Also, I presume a grounding problem might not manifest through the headphone output? That's the one I'm a bit more miffed by. Audio over USB through headphones is fine, great even. The reason I wanted to buy a DAC like this! At least on the three pairs of headphones I've tested with (no balanced yet, those will come with a headphones upgrade later).

edit - In the meantime I'm giving up and using optical. Hope Fostex can hook me up with a quality grounded power supply. I kind of nuked my own worry that the phono output was faulty on my unit by plugging optical back in. The phono out is still used to go to the speakers even if its optical bringing audio in, and everything works great over optical. So it really does have to either be a power supply grounding fault or a USB issue. I'm not against using optical it's just frustrating as hell to buy a USB DAC and not be able to figure out why you're getting really bad feedback/pops over USB 24bit/96k is more than enough for me, heck, it's overkill anyway I just use my PC for listening to music, working and occasionally some light gaming. But your issues being fixed by another power supply gives me hope.

 

[davehutch]

Thanks.

One question I could throw at you is would a grounding problem not manifest itself over an optical connection? I know the answer to many pops, crackles and hums is "just use optical", but I don't know the science behind why that works

Also, I presume a grounding problem might not manifest through the headphone output? That's the one I'm a bit more miffed by. Audio over USB through headphones is fine, great even. The reason I wanted to buy a DAC like this! At least on the three pairs of headphones I've tested with (no balanced yet, those will come with a headphones upgrade later).

edit - In the meantime I'm giving up and using optical. Hope Fostex can hook me up with a quality grounded power supply. I kind of nuked my own worry that the phono output was faulty on my unit by plugging optical back in. The phono out is still used to go to the speakers even if its optical bringing audio in, and everything works great over optical. So it really does have to either be a power supply grounding fault or a USB issue. I'm not against using optical it's just frustrating as hell to buy a USB DAC and not be able to figure out why you're getting really bad feedback/pops over USB 24bit/96k is more than enough for me, heck, it's overkill anyway I just use my PC for listening to music, working and occasionally some light gaming. But your issues being fixed by another power supply gives me hope.

I don't know the answer to that one I'm afraid. I'm only going by hunch and my own experience but I don't know the electrical theory I'm afraid. My own issue was a small electrical shock from my IEMs, whether or not I used USB or optical input to the Fostex. Fostex were very helpful and fast too.

 

[Audioboxer]

I don't know the answer to that one I'm afraid. I'm only going by hunch and my own experience but I don't know the electrical theory I'm afraid. My own issue was a small electrical shock from my IEMs, whether or not I used USB or optical input to the Fostex. Fostex were very helpful and fast too.

Gotcha, much appreciated with all the advice and things to try. The one thing we have discovered is the plug I have has the fake prong, so it's one of the last avenues I have left for trying.

The internet is full of people having issues with DACs and USB, so it seems like it's a minefield. Many issues do seem to be sorted with a powered external USB hub. Something which I have tried.

Until I hear back I'll just use optical!

 

[Audioboxer]

Just a small update to say Fostex customer service UK are great

In the first instance I can send you a grounded power supply which may well correct the problem please confirm your full address & contact number.

Here is hoping my USB issues get fixed! Just been running optical in the mean time with no issues.

I guess I should probably add I love this wee DAC too

 

[davehutch]

Just a small update to say Fostex customer service UK are great



Here is hoping my USB issues get fixed! Just been running optical in the mean time with no issues.

I guess I should probably add I love this wee DAC too

Yes, they certainly are. Here’s hoping

 

[Audioboxer]

Yes, they certainly are. Here’s hoping

Arrived today, sadly it doesn't help, so I'm all out of ideas. I guess I would need to now troubleshoot by means of trying some sort of input that isn't my own laptop/PC to test if it's all to do with the USB source. I've tried getting my Galaxy S20/Nintendo Switch outputting audio with a USB C converter but neither seem to work.

That and/or getting another set of speakers and testing them. I only have two pairs that are powered speakers, both exhibit the same issue. I don't think it's the speakers though as they work fine over optical.

So props to Fostex for supplying a grounded power supply, but I'm no closer to finding out why one of the phono outputs on the Fostex seems to deliver a sharp pop to whatever speaker its connected to when it's over USB. A pop on power on, and then pops during certain operations like moving the YouTube seek bar or if there is no audio output for a while, the next time there is (easily demonstrated with having nothing playing and moving the windows control taskbar volume slider).

I have been reading a load of horror stories across the web where people just struggle to get USB working without a whole host of issues. Some saying its even down to the fault of Windows 10.

Optical has been working fine the past few days, so if all else fails I'll just stick with it. I still appreciate the plug anyway, it rules out any future issues like yours.

 

[Audioboxer]

While I've had no luck with USB and have now just stuck with optical, I have bought a new set of speakers for another room in the home I will be able to try shortly, the Kanto YU4. So I'll see how I get on with these! Not expecting any difference mind you, but you never know.

 

[davehutch]

While I've had no luck with USB and have now just stuck with optical, I have bought a new set of speakers for another room in the home I will be able to try shortly, the Kanto YU4. So I'll see how I get on with these! Not expecting any difference mind you, but you never know.

Hope you get to the bottom of it

 

[Audioboxer]

Hope you get to the bottom of it

Thanks, but no such luck. Same issue with these Kanto YU4 speakers (the audible pop out of one speaker).

I asked Fostex for some more help but no one has responded from customer service yet. I guess I might just be sticking to optical only from PC lol.

If it's not a faulty unit I have, and I don't think it is that, the only thing I have left to test is one of those decent quality USB isolators (the £50 ones that can do full speed USB, not the slower ones around £15). Be surprised if that works though given I've tried powered USB hubs and a laptop running on battery.

Only thing I haven't managed to try out is another operating system than Windows 10.