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Hardware Teardown of Schiit Fulla (V2) DAC and Headphone Amplifier

amirm

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#1
I recently performed a review of Schiit Fulla DAC and Headphone amplifier. This is a follow teardown of the unit.

Let's start with top down view of the unit:

Schiit Fulla V2 Front PCB.jpg


Starting on the right side we see the typical USB controller (Cmedia CM6631A) driving an AKM AK4490EQ DAC. An external flash IC holds the firmware for the device.

Here is the Cmedia CM6631A top level features:

upload_2018-5-7_18-11-36.png


And AK4490EQ:

upload_2018-5-7_18-12-41.png


The output of the DAC goes to a pair of TI LMH6643MA amplifiers which output 75 milliamps:

upload_2018-5-7_18-14-24.png


Notice the short circuit protection. From what I recall, shorts caused the unit to shut down though, requiring plugging and unplugging the USB cable. Regardless you should be able to plug and unplug the headphone without worrying about damaging the output stage.

Since the distortion products were very different in each channel, I zoomed in to see if there were any part disparities between the two channels:

Schiit Fulla V2 Amplifier IC.jpg


I could not spot any. You are welcome to scrutinize it more and see if you can find it. :)

Looking at the back side of the PC Board we find:

Schiit Fulla V2 Back PBC Poor Solder Quality #2.jpg


Typical poor soldering job from Schiit. :( Solder splatter is clearly visible. Imagine these getting loose and shorting out the pins on the surface mount ICs. Their pin pitch is extremely small and these balls could easily cause a short.

More here:

Schiit Fulla V2 Back PBC Poor Solder Quality.jpg


The red solder mask keeps those from making an electrical connection. But also allows them to easily come loose causing potential shorts. It would take 2 seconds to blow or brush them off.

Conclusions
The Schiit Fulla DAC and headphone amplifier has a simple architecture allowing its low cost of manufacturing. The most glaring problem with it is the horrible hand soldering job of through hole components, creating potential for shorts. This is like a restaurant that doesn't use soap to wash its dishes. You may not get sick from eating there but it sure is wrong. This is something you do not see even from low cost manufacturer.
 

Wombat

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#2

stalepie

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#3
The Fulla 2 generally sounded good to me, but it had a scratchy pot. I never knew what the problem was. I sent it back at my expense and got it temporarily repaired -- the problem started coming back a few days later. Several other people on Head-Fi had the same problem. I put in a lot of Deoxit, which got rid of most of it (at least for the time being) and sold it to someone else on the forum at about half price. I just didn't understand why its main feature (the pot) would have a problem like that on a new device. I wondered if they were sourcing used parts, or just have a dusty facility. I don't know anything about it. Maybe it just wasn't soldered correctly.
 

Sythrix

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#4
Looks like an incomplete solder fill on the third one down in the last picture, which speaks of a rushed job. I can see why they have such high QC issues.

I'm exceedingly glad I don't have to use my Magni 2U anymore. Might take it apart. Or I could send it to you as a donation Amir, if you want to measure it, take it apart then sell it off or keep it or whatever.

Edit: It's not that I think it will measure badly, I just feel uncomfortable using it after seeing multiple Schitt teardowns. They obviously do things in a hurry and without a lot of care, so that will weigh on my mind when/if I use it again.
 
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Wombat

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#5
The Fulla 2 generally sounded good to me, but it had a scratchy pot. I never knew what the problem was. I sent it back at my expense and got it temporarily repaired -- the problem started coming back a few days later. Several other people on Head-Fi had the same problem. I put in a lot of Deoxit, which got rid of most of it (at least for the time being) and sold it to someone else on the forum at about half price. I just didn't understand why its main feature (the pot) would have a problem like that on a new device. I wondered if they were sourcing used parts, or just have a dusty facility. I don't know anything about it. Maybe it just wasn't soldered correctly.

DC on the pot can cause scratchiness. It may be a design issue.
 

amirm

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#6
Looks like an incomplete solder fill on the third one down in the last picture, which speaks of a rushed job. I can see why they have such high QC issues.
Ah, good eye. You are right.

I'm exceedingly glad I don't have to use my Magni 2U anymore. Might take it apart. Or I could send it to you as a donation Amir, if you want to measure it, take it apart then sell it off or keep it or whatever.
Sure. Just send it along. :)
 

mindbomb

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#7
The fiio e10k uses those same amplifier chips iirc. They are unusual since they are not made for audio, and have really high slew rate and bandwidth.
 

έχω δίκιο

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#8
amirm said:
Since the distortion products were very different in each channel, I zoomed in to see if there were any part disparities between the two channels:
...
I could not spot any. You are welcome to scrutinize it more and see if you can find it.
The most likely explanation is that at least one of the opamps is a counterfeit. The counterfeiters take a cheap opamp that's somewhat compatible, remove the markings, mark it as a more expensive part, and sell it for a big profit. There are operations in China that do this on a large scale. QC/QA inspections on boards and finished goods are almost always visual/functional (i.e., does it work?) rather than performance based, so they get away with it.
 

Wombat

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#9
The most likely explanation is that at least one of the opamps is a counterfeit. The counterfeiters take a cheap opamp that's somewhat compatible, remove the markings, mark it as a more expensive part, and sell it for a big profit. There are operations in China that do this on a large scale. QC/QA inspections on boards and finished goods are almost always visual/functional (i.e., does it work?) rather than performance based, so they get away with it.
Most likely? Is that a subjective opinion or more supportable?
 

έχω δίκιο

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#11
Most likely? Is that a subjective opinion or more supportable?
Based on my years of experience, the pervasiveness of counterfeit parts in the supply chain, the cost of the genuine part, the measured performance, physical aspects of the parts' cases and leads, and the appearance of the lettering, it's the most likely explanation.

You may find these articles interesting:
https://zeptobars.com/en/read/OPA627-AD744-real-vs-fake-china-ebay
https://zeptobars.com/en/read/Ti-NE5532-real-vs-fake-opamp
https://e2e.ti.com/support/amplifiers/etc_amplifiers__other_linear/f/18/t/677357
 
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#12
Typical poor soldering job from Schiit. :( Solder splatter is clearly visible. Imagine these getting loose and shorting out the pins on the surface mount ICs. Their pin pitch is extremely small and these balls could easily cause a short.

The red solder mask keeps those from making an electrical connection. But also allows them to easily come loose causing potential shorts. It would take 2 seconds to blow or brush them off.

The most glaring problem with it is the horrible hand soldering job of through hole components, creating potential for shorts. This is like a restaurant that doesn't use soap to wash its dishes. You may not get sick from eating there but it sure is wrong. This is something you do not see even from low cost manufacturer.
A few years ago I switched board houses--to the one here in California that Schiit uses (I won't name them). Really nice people, very competitive prices. But communication, delivery, and delivery were abysmal. We had to QC every board not just for solder flakes, but for full on shorts between pins of high-current regulators. I have at least $3K in scrap boards in a box somewhere--all courtesy of that firm that Schiit just loves (they are only about a 20 minute drive from their offices so there is that.)
Needless to say, we switched to a much better firm--well before we went into production of the sophisticated, 175 parts, both sides of 4-layer PCB, including BGA parts and tiny 0402s, UltraCap power supplies. Having any solder flakes on that crowded board would be disastrous!
 

Jimster480

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#14
Looks like a solid unit outside of the poor soldering, maybe they are hand soldering each of these? It surely doesn't look like any wave soldering job?

The biggest problem is with the problems in the USB interface....
 

έχω δίκιο

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#15
Looks like a solid unit outside of the poor soldering...
The measured performance in the earlier review isn't what I would call solid. The Schiit had 15-35db higher noise floor than a Topping D30 and the channels displayed "wildly different" noise and distortion from one another. Yeah, I know it's only $99 MSRP, but there are other units in that price range that significantly outperform it.
 

Jimster480

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#16
The measured performance in the earlier review isn't what I would call solid. The Schiit had 15-35db higher noise floor than a Topping D30 and the channels displayed "wildly different" noise and distortion from one another. Yeah, I know it's only $99 MSRP, but there are other units in that price range that significantly outperform it.
I wasn't talking about the performance, I was talking about the physical construction inside.

I was the one who sent the Fulla2 in to be tested. I think it sounds like crap and its easily the worst piece of audio kit I have..
I just didn't actually feel like opening it up incase I broke it and couldn't test it in the future.
 

stalepie

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#18
The measured performance in the earlier review isn't what I would call solid. The Schiit had 15-35db higher noise floor than a Topping D30 and the channels displayed "wildly different" noise and distortion from one another. Yeah, I know it's only $99 MSRP, but there are other units in that price range that significantly outperform it.
The D30 is just a DAC, though and costs more. It's also a larger unit.
 

έχω δίκιο

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#19
The D30 is just a DAC, though and costs more. It's also a larger unit.
  • The prices are essentially the same. A D30 is $120 including 2-day shipping and a Fulla 2 is $118 with 2-day shipping (after their 1-3 days between when you order and when they ship).
  • The sizes are both in the compact class, with neither being small enough to comfortably slip into a shirt pocket or too big to carry one-handed.
  • Yes, the D30 includes a headphone amp, and if we were talking about a 6dB difference in noise, you'd have a point, but we're talking about a 15dB-35dB difference in noise floor.
 

stalepie

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#20
  • The prices are essentially the same. A D30 is $120 including 2-day shipping and a Fulla 2 is $118 with 2-day shipping (after their 1-3 days between when you order and when they ship).
  • The sizes are both in the compact class, with neither being small enough to comfortably slip into a shirt pocket or too big to carry one-handed.
  • Yes, the D30 includes a headphone amp, and if we were talking about a 6dB difference in noise, you'd have a point, but we're talking about a 15dB-35dB difference in noise floor.
The D30 is about the size of the Modi (https://www.audiosciencereview.com/...30-versus-schiit-modi-2-dac-review-jpg.12682/), which is larger than the fulla 2 or fulla 1. It doesn't have a headphone amp. You buy the $120 A30 to stack on top of it, so for both dac+amp in this combo it is $240, not $99 like the Shit Fulla 2.

edit: sorry, A30 seems to cost $109.99 on Aliexpress, not $120.
 
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