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Fixing Hum/Buzz issues with Schiit Jotunheim Headphone Amplifier

amirm

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#1
In my review of Schiit Jotunheim by chance I noticed that the upper part of the case is not grounded. As such, it allowed the transformer to induce hum into the output of the amplifier. Here are the measurements showing such:



A jumper between the drilled holes that are not insulated and the back RCA jack shield got rid of the noise:



This quick article is about accomplishing the same without said jumper.

Note that this is both a performance issue and potential shock hazard. Metal cases on a three-pronged outlet must be security connected to mains safety ground pin. While my fix will also help with the safety issue, it is insufficient. A proper screw and ground wire is necessary for proper safety grounding.

Start by disconnecting all cables, especially the power one. There are lethal voltages inside and you can easily shock and kill yourself. So check and double check that you have unplugged the mains cable.



The case is tricky to take apart and that actually contributes to the problem. First, take off the large volume control by unscrewing its tiny set screw (be careful to not round it). Behind it are a nut and washer which you need to remove with a pair of pliers Once there, you have this:

Schiit Jotunheim Hum fix front panel.jpg


Now the hard part. Pull the case forward some. It will put up fair amount of resistance at first. Slide it forward with fair amount of force and it should move at least a quarter of an inch. It will then get stuck. The pins are in keyholes and if you slide the case too far, they will latch on the opposite side. I found that putting the case upside down on my lap, sliding it forward and back, and eventually tilting it to clear the volume control shaft works.

Don't be concerned if you can't get it off immediately. Go ahead and curse fair bit as I did every time i tried to open and close it. It is necessary and gets you refocused on getting it open. It will eventually come apart and you see the inside guts:
Schiit Jotunheim Hum fix inside enclosure.jpg


There are four pins in the top lid that slide into those keyholds. As luck would have it, they are not insulated like the rest of the case is. So what you need to do is sand/file off the narrow part of the keyhole where the pins seat when closed. I used a diamond file and kept the unit upside down to make sure nothing fell in there. Alternatively you can use a sharp pick and scrape off the paint.

Here, you need to have an ohmmeter to check that you have sufficiently exposed bare metal. Connect the probes to the different keyholes and you should get connectivity in the 1 ohm or less.

The powder coating or whatever they have used is very tough. It took fair amount of doing to get the paint exposed. A better solution is to take the entire unit apart and use a rotary tool to get in there and really clean up the paint. Better yet you could sand of the paint around the top of the keyholes to expose even more metal for good contact. Be sure to do the same in the lid. The issue here is that these components may rust. Use your own judgement.

Turns out that the above is NOT sufficient because even the bottom of the case is ungrounded! All that stays between you and electric shock is that powder coat. To fix that, you need to take out these screws and like above get rid of the pain that exists on the chamfer in the case:

Schiit Jotunheim Hum fix bottom enclosure.jpg


Screw them back in and check with a multimeter that the keyhole area you sanded off now reads a low resistance with either the mains safety pin in the IEC connector or the outside of the RCA connectors. Keep sanding and exposing fresh metal until you get to a near short (1 ohm or less ideally).

Then put the lid back on following the reverse process (yeh right, as if it is that easy). Once you put the case all together and before putting the volume knob and screw back on, run this test to make sure there is good continuity:



Unlike the above picture where I tested before this mod, you should get a short/1 ohm or less resistance. I had to be careful with my loaned unit and I think I got it down to 2 ohms or so.

That's it.

I am hoping that Schiit responds and makes this fix for owners. But if not, you can improve things with this mod which takes 10 to 15 minutes.

Post here if you have this problem and the mod helps things.

As is always the case, you make these mods at your own risks. You can easily damage the unit once inside. So be careful.
 
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amirm

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#3
:)

Pain was definitely in my mind as I dealt with this case. This should be a case study in how NOT to design a case. One tiny wrong move and one of the pins would lock up, not letting you either close it or open it. You have to align four pins and the front shaft, plus the switches and headphone jacks to open the thing. All to avoid putting foru screws in there??? Which would have also solved the grounding problem?
 
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#4
Could the design be considered illegal under US law? I hope Schiit really takes their responsibility and tries to fix this. But I know they won't, they'll just claim everyone experiencing this are lying. Can't wait to find a good alternative in the price point and just get rid of this piece of shit
 
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#5
:)

Pain was definitely in my mind as I dealt with this case. This should be a case study in how NOT to design a case. One tiny wrong move and one of the pins would lock up, not letting you either close it or open it. You have to align four pins and the front shaft, plus the switches and headphone jacks to open the thing. All to avoid putting foru screws in there??? Which would have also solved the grounding problem?
Is it out of incompetence, just being cheap or sheer laziness? I mean this is next level stupid if they did not think of this. I'm not even an electrical engineer and I get how stupid this is
 

amirm

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#6
It appears to be a design oversight. The usual scheme looks like this:



All I can tell so far is that they just connect the mains earth to signal ground on the PC board and that is basically it. No dedicated chassis ground connection per above.

If they had not painted the specific parts I mentioned, it would sort of work but still not to the degree necessary.
 

amirm

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#7
Could the design be considered illegal under US law?
The only safety marking on the back is CE which allows self-certification (i.e. no way to know if the tests are really passed).

North America equiv. for this part is UL and there is no UL marking on Schiit Jotunheim. UL requires actual testing and verification and hence, costs money. With an internal mains power supply in this unit, it needs to come with UL certification as expensive and painful that process may be. If the vendor doesn't want to deal with this, they should use an external wall-wart.

I don't want to give legal advice but UL marking is not mandatory in US. Should there be product liability though, it is quite helpful for the manufacturer to have one.
 
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#8
The only safety marking on the back is CE which allows self-certification (i.e. no way to know if the tests are really passed).

North America equiv. for this part is UL and there is no UL marking on Schiit Jotunheim. UL requires actual testing and verification and hence, costs money. With an internal mains power supply in this unit, it needs to come with UL certification as expensive and painful that process may be. If the vendor doesn't want to deal with this, they should use an external wall-wart.

I don't want to give legal advice but UL marking is not mandatory in US. Should there be product liability though, it is quite helpful for the manufacturer to have one.
Well they are still liable even if it's self tested

" By affixing the CE marking on a product, a manufacturer effectively declares, at its sole responsibility, conformity with all of the legal requirements to achieve CE marking which allows free movement and sale of the product throughout the European Economic Area.

For example, most electrical products must comply with the Low Voltage Directive and the EMC Directive; toys must comply with the Toy Safety Directive. The marking does not indicate EEA manufacture or that the EU or another authority has approved a product as safe or conformant.[4] The EU requirements may include safety, health, and environmental protection, and, if stipulated in any EU product legislation, assessment by a Notified Body or manufacture according to a certified production quality system. The CE marking also indicates that the product complies with directives in relation to "Electro Magnetic Compatibility"[5] - meaning the device will work as intended, without interfering with the use or function of any other device"
So if it's deemed they break any of these rules the CE marking have to go, and no respectable store in the EU would sell a product without one
 

Jimster480

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#10
This is really really bad on their part, even worse than the horrible measurements...
@amirm you should check to see if other products have similar issues.
 

jsm59

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#11
+1 on Jimster's remark; checking other of their products for this hazard/hum issue. Seems the MANI hasn't been tested here (?) and I'm thinking of one as it does generally seem to get good comments. (These are anecdotal and not based on measurements). However, out of principle, I already don't care for the arrogance I pickup watching most Vids wih the that Co.'s owners. Finding a similar issue would knock it off my short list. (Just getting back to vinyl).
 

Grave

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#12
Shit was was famous for their amplifiers damaging headphones a few years years ago, although they supposedly fixed that issue.

Also, every time I tell people Shit is bad I am "trolling."
 
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#13
+1 on Jimster's remark; checking other of their products for this hazard/hum issue. Seems the MANI hasn't been tested here (?) and I'm thinking of one as it does generally seem to get good comments. (These are anecdotal and not based on measurements). However, out of principle, I already don't care for the arrogance I pickup watching most Vids wih the that Co.'s owners. Finding a similar issue would knock it off my short list. (Just getting back to vinyl).
I would recommend Pro-ject phono box if you want to ditch Schiit
 

amirm

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#16

amirm

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#17
This is really really bad on their part, even worse than the horrible measurements...
@amirm you should check to see if other products have similar issues.
It only impacts units with internal power supplies. The only such unit I have right now is the loaned Yggdrasil and while I can't power it down to really check, it seems fine. It has a bunch of screws holding the lid down which give nice electrical connection. It is the friction fit with the Jotunheim that is the problem.
 

amirm

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#18
Jason is looking into it and will add a grounding test procedure for the Jotunheim and Lyr 3 production:
https://www.head-fi.org/threads/sch...view-head-fi-tv.818323/page-389#post-14362885
Thanks for relaying the information there :). Please let Jason know that in addition to the keyholes, the bottom case also has paint in the chamfer where the grounding screw goes. I first fixed the keyhole and was surprised it was still not grounded until I discovered the issue with the bottom screw as I documented in my original post.
 

amirm

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#19
Well they are still liable even if it's self tested

" By affixing the CE marking on a product, a manufacturer effectively declares, at its sole responsibility, conformity with all of the legal requirements to achieve CE marking which allows free movement and sale of the product throughout the European Economic Area.
Most definitely. There can be serious fines for falsification of the mark.
 
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