Need help fixing distortion

[GavinK]

Hello everyone,
New to the forums; I’m a Hi-/Mid-fi headphones enjoyer with a mix of studio and HiFi equipment. I started upgrading the playback quality of my studio with HiFi components and have since upgraded massively in sound quality and am never going back!

That said, I have an issue. I’m hoping someone hear can point me in the right direction.. in “studio land” they refuse to help people who “believe audiophiles”…

My setup is as follows:
I have an iFi power cord (I think it’s the Nova from memory) into the Stellar P3 powerplant. Output goes through an Audioquest Tornado (HQ) into the RME Fireface 802 AE USB audio interface. Connected with my Mac Mini M4 with a Curious Cable USB into a galvanic isolator (Intona 7455-C..? ..also from memory) into Audioquest Carbon USB.
I use a Hifiman HE1000 Unveiled as headphone, with the default cable, coming from the headphone output (11/12) off the RME directly (no separate amp).

Everything sounds amazing, except sometimes, I hear a bunch of distortion. This always happens only at certain tracks and it’s always at a loud part, most of the time when there’s a quick rise in volume. At first I thought it was clipping, but I’m playing back digitally; lowering the digital volume changes nothing, lowering the physical potentiometer changes nothing and the headphone amp isn’t overdrawing any current anywhere (not that I would believe, at least). Changing settings in Audirvana changed nothing; turning all DSP on or off changed nothing. Even playing back the track through Finder directly changed nothing; the distortion is still there.

The strangest part is that the worst distortion happens on Don’t Know Why from Norah Jones (album purchased from Qobuz, 24bit/192kHz). I also get it on different tracks on that album. Same issue, but less present, on Back to Black from Amy Winehouse. Yet, if I take a hit from the Bee Gees, I can blast it at full volume, no issue. Coldplay X&Y.. same thing, no problems.
It seems odd to me that the one track Paul is the most fan of, is the track that has the most distortion in my system. There has to be something going on.. but what?

Does anyone have any ideas? - I’m pretty much with my hands in my hair on what’s causing the issue and how to fix it at this point. Googling has brought me nothing, I keep ending up at “it’s clipping” but I’m quite sure that’s not it, unless I have missed something.

Much appreciated,
Gavin

Another update:
Tested the track Don’t Know Why on the new KEF LSX II’s in the living room. There is significantly less distortion on these speakers.
At this point I’m guessing it’s the DAC in the RME, which simply cannot handle these types of waveforms and ends up distorting them. I’ll need to go into the rabbit hole of buying a seperate DAC to see what that does.. maybe someday, for now I’ll have to live with it I guess.

Small update:
I tested Don’t Know Why putting the output through the (digital) oscilloscope; the waveform looks like this:

Every time I hear distortion, this “dip” seems present.
Maybe this information can help someone?

[allan.thunes]

Man. All I can offer is a welcome aboard and good luck figuring this one out. Odd symptoms are likely to equally odd / elusive causes.
I’m completely unfamiliar with your setup so have nothing specific. Is this an always been or something new problem?
If the distortion is at least consistent are you able to test individual components in other setups to isolate a problem child?
Can you play the same source material through another setup?

[Elk]

Welcome!

[adifferentpaul]

My gut instinct tells me to say it could be the wires going to the headphones. Move them around. Unplug & replug them.

[GavinK]

Thank you for the welcome greetings!
It’s the least one can do.

Hmm.. I remember the problem going back to when I purchased the album, which is before the USB conditioning and before the HE1000 (I still used the Arya Organic back then). The issue has persisted through both.

I’m quite sure it’s the RME, but I’m unsure if it’s the DAC or the headphone amp and since it’s an integrated it’s hard to test. It’s also hard to test because I would need a seperate DAC and headphone amp to verify it really is the RME.
Yet, if could also just be some kind of setting regarding gain. But I wouldn’t know.
Maybe I should contact RME to have them think about this, because I don’t think they’d like to hear their headphone amp distorts.

We’re getting a few KEFs for the living room soon (actually, they arrive today). I’ll play back the album through Qobuz on them, see how it sounds there.

[GavinK]

Thanks for your reply! Unfortunately that hasn’t solved the problem.
It’s also not the female jack connector in the RME, because it has two headphone output ports and both have the same issue.

[aangen]

It would be weird if the RME was messing up. I do a reset on mine every now and then. I had to type a question into google to find out how to do it. It’s very easy. And the reset made everything RME related very happy.

Also, I own the Intona device. It didn’t work well and the guy from whatever his business is called, he makes and sells the boring May DAC. Anyway, he was less than useless. We had words.
I figured out how to get it to work. Bah. After a few weeks I took it out of my system and it is now in protective custody. I won’t let anyone torture themselves with it. No.

Intona don’townah.

[GavinK]

Your remark about the Intona made me laugh. I personally purchased the Intona from a medical supplies dealer, who has nothing to do with Hifi. Delivery and installation were easy and I got helped very well. To me it makes a massive difference, so I’m keeping it. Sad to hear you got bad support.
The issue already existed before the Intona arrived, so I’m quite sure it’s not the cause.

I have not tried to do a reset on the RME yet! I will google it and try and get back to you. Thanks for replying!

[BruceAB]

I don’t see any distortion in that waveform so I doubt that’s pinpointing the problem. I will also say that I have that album on SACD (Analogue Productions) --that’s my favorite song on my favorite album-- and in the first verse of “Don’t Know Why” Norah’s phrasing is such that she puts a lot of emphasis on certain notes – “I WAITED til…”, “I LEFT you…”, etc. My system struggles with it, too, and that track has become one of the standard tests that I run when I am trying to understand why my system, too, distorts sometimes when playing back. I’m driving speakers that are difficult loads so it could be in my case that my amplifier just doesn’t have the needed current in reserve when I play it loud. That’s not likely to be your problem if you are listening with headphones. Another one of my test tracks is Alan Parson Project’s I Robot album on MOFI SACD, track 4 “Breakdown” if you are into classic rock.

[aangen]

I have dbPoweramp and it comes with a program to convert files from one format to another. If you have a file that has issues playing, perhaps convert it to FLAC or AIFF or WAV and try it after the conversion. Just a thought.

With Maestro two full CD recordings from the same source cause Maestro problems and it rejects all the files. (Roon and Foobar have zero problems with the files) Originally they were FLAC files. I converted them to AIFF and Maestro doesn’t have problems with them anymore. I probably won’t convert them back to FLAC. LOL.

[GavinK]

You’re EXACTLY on point! It’s precisely these words where I get the distortion. In fact the graph I posted is of the word “waited” in particular. Maybe it’s partially also in the track? - Either way, interesting to hear your system has a similar issue.
The RME headphone output is of very low impedance, but there’s plenty of power to go to much louder volumes. Yet it does seem like a current flow issue. Hmm…

EDIT: Could it have something to do with the slew rate of the headphone amp / DAC?
The graph shows the digital signal going into the DAC btw, I believe, not exactly sure where it measures.

[GavinK]

Hmm.. I’ll have to try that, though I doubt it’ll make much of a difference. I use AIFF all the time, FLAC sounds even worse than MP3 (my hot take) so it really is the actual WAV file and not a file format issue that I’m playing back.
But thanks for thinking about this because I hadn’t considered it yet. I will certain convert (probably with Audacity) and let you know.

[GavinK]

Unfortunately, the RME Fireface 802 doesn’t have factory reset…
The manual says the way to “reset” is to switch it off and leave the power cord out for a while. Did exactly this but unfortunately to no avail. Everything is managed digitally through TotalMix; resetting that to factory settings also had no effect.

[wijber]

@GavinK

FLAC sounds even worse than MP3

…something has to be wrong with your system

[aangen]

TotalMix was what I used to reset mine. When I googled it said open TotalMix and do this and this.

Thinking about your issue I don’t believe any of this will help.

I check the dynamic range of every track I add to my library. I have software that makes it very easy. 40% of the tracks I test have tracks that go over 0dB. That’s solid clipping during the segments that go over 0dB.

What is the source of this track? CD rip? Digital download? I would love to look at it with some nice tools that I have. Her recordings generally are recorded very well. But this could be a live recording that got too hot and it wasn’t caught. Maybe find something else to listen to.

DOCTOR! IT HURTS WHEN I DO THIS!
Well don’t do that then.

[BruceAB]

I ripped the Naomi Jones CD to flac files and this is the waveform when she sings “left”. The second is a magnified view of the first --the dots are each PCM sample. The left channel has a little more amplitude that the first so it is the one to watch. The one peak you can see in the picture is one of the highest on the entire track and it almost makes it to zero, but not quite. If the signal were clipped you’d be seeing several samples in a row that are at exactly the same height so the top of the waveform would be flat. Not the case here. BTW I’m sure the mastering engineer raised levels as high as possible but was careful to not clip and I saw few signs of compression. Good CD!

[aangen]

That looks fine waveform wise.

[kcleveland123]

However, if there are any downstream gain stages > 1 (0 dB) you could still easily have clipping if you’re driving the signal above the power supply rails.

[GavinK]

I fully agree that there’s no issue with the waveform. But there’s distortion (a lot of it) at the output anyway. It has to be something internal, but I’m not sure what it is and whether it can be fixed or not.

[GavinK]

Exactly. However.. if I bring down the digital signal by, let’s say -5dB (which is a lot), when I up the volume on the headphone amp output to compensate for this loss (by +5dB), I hear exactly the same distortion at exactly the same point.
Which is why I’m starting to lean more towards the idea that the DAC is the issue and can’t properly reproduce the signal. Don’t know why though.