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Teardown of the Emotiva DC-1 DAC

amirm

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#1
This is a teardown of the Emotiva DC-1 DAC and headphone amplifier as a follow up to my review of that unit (see https://www.audiosciencereview.com/...surement-and-review-of-emotiva-dc-1-dac.2306/).

Here is an overall shot of the unit:

Emotiva DC-1 DAC and Headphone Amp PCB inside 20180202_132513.jpg


Overall layout is good. AC mains comes in from the right, goes up to the transformer. Below that we have the digital cluster and flow is to the left ending in analog and headphone outputs.

Immediately though, there is a major source of concern. Check out the IEC plug:

Emotiva DC-1 Missing Ground Lug 20180202_132521.jpg


We have a 3-prong, grounded IEC socket but the ground lug doesn't go anywhere! It must be connected to the case as this is metal and an electrical short can energize it. Only a double insulated piece of equipment can be run on two wires. Which this is not.

This is a major safety flaw! I can't recommend purchasing this equipment on this basis!

And look at how the mains hot leads are nicked due to inadequate room for them:

Emotiva DC-1 Pinched mains wire 20180202_132529.jpg


There is plenty of space to move this board forward to alleviate this problem:

Emotiva DC-1 Mains Input Filter 20180202_132816.jpg


Manufacturing people should have complained about this and forced a simple design change.

Moving on, here is the main digital cluster:

Emotiva DC-1 main ICs 20180202_132756.jpg


We see the classic CMEDIA USB input chip.

upload_2018-2-2_14-53-16.png


And AKM4118 digital audio receiver:

upload_2018-2-2_14-53-56.png



Not so typical is the asynchronous sample rate converter by Analog devices AD1896. This allows the DAC to run at a constant rate by resampling the input as it drifts. It is said that it reduces jitter but as my measurements show, they did not get there.

upload_2018-2-2_14-54-48.png


What is also unusual is the inclusion of that Altera FPGA. I am not sure why it is necessary. Other DACs implement similar functionality without the expense of an FPGA.

A pair of Analog Devices AD1955A provide the digital to analog conversion.

upload_2018-2-2_14-51-26.png


After some buffering, the output of the DAC goes through a couple of MUSES analog volume controls:

Emotiva DC-1 Muses Volume Control 20180202_132858.jpg


upload_2018-2-2_14-57-24.png


I am not sure if the OPA 2134 are for buffering the analog input or output.

upload_2018-2-2_14-58-31.png


Next and final stage is the headphone amplifiers which are sitting next to the voltage regulators:

Emotiva DC1 regulator and headphone amplifiers 20180202_132606.jpg


BUF634T provides the headphone amplification:

upload_2018-2-2_15-2-25.png



Some more ugly news in the form of dirt-cheap and unreliable electrolytic capacitors from Decon used throughout:

Emotiva DC1 cheap capacitor 20180202_132636.jpg


Note the filter caps that were assembled but then cut out of the board. Hard to imagine why.

BTW, the larger caps are Emotiva branded and have no temperature rating. Sitting close to the heat sink guarantees short life.

Another thing that makes me grumpy is this hand soldering job:
Emotiva DC-1 hand soldering 20180202_132744.jpg


I prefer PCB mounted jacks to this ugly bit of work.

Conclusions:
From safety point of view, the Emotiva DC-1 gets a failing grade from me. There is no excuse for not grounding the chassis to the ground terminal of the IEC jack.

Overall layout good with fair amount of engineering going into the many components there.

Hand soldering work is poor as is the horrible selection of cheap and unreliable capacitors that are bound to fail. Not acceptable at this price point.
 

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DonH56

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#2
FPGA used for control functions maybe? Where is the ADC for the analog inputs?

Agree all they had to do was move the AC input board a little, wonder how that slipped through... Maybe it's corrected on the DC-2 but not anxious to find out.
 

Don Hills

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#3
Yep, not enough heat when soldering to those sockets. Very likely to fall off if you pry at it. The correct way is to fit a tag washer (washer with a solder tag sticking out the side) when mounting the socket. They appear to have used insulating washers between the socket and chassis, but it doesn't look like they mounted them properly. There's a risk of the socket slipping sideways and contacting the chassis, potentially causing ground loop problems.
 

RayDunzl

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#5
Is that unit new or used?
 

amirm

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#6
Is that unit new or used?
Used. Belongs to Sal. There is a good layer of dirt on it courtesy of the convection heat due to that heatsink and power ICs on it.
 

March Audio

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#7
Hi Amir,

Interesting teardown. Just one point regarding the earthing. If the unit has been designed in accordance with class ii rules it does not need an earth connection regardless of the metal chassis. My understanding is that there needs to be a 6mm air gap or layer of insulation between any live areas and the chassis. In Europe it will be designated by a squarecinsideva square symbol on the case.
 

March Audio

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Wayne

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#9
There is no excuse for not grounding the chassis to the ground terminal of the IEC jack.
The pinched and nicked mains coupled with the lack of grounding could have serious consequences........ Not good!

Thanks for the teardown report!
 

DonH56

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#10
There is an 8-bit micro in there which should do the control stuff.

It doesn't digitize the input. It is just an analog path on the way out to the headphone.
Ah, duh, thanks Amir. Head's fuzzy today, work and family health issues, sorry.

They don't have to ground the chassis to the safety ground if they follow the rules for isolation, but it's a good idea. No excuse for pinching incoming power leads like that. :eek:
 

amirm

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#11
Interesting teardown. Just one point regarding the earthing. If the unit has been designed in accordance with class ii rules it does not need an earth connection regardless of the metal chassis. My understanding is that there needs to be a 6mm air gap or layer of insulation between any live areas and the chassis. In Europe it will be designated by a squarecinsideva square symbol on the case.
I know about class II compliance while using a metal case but it requires dual means of protection against shorts. No way this complies with that. The wiring to the transformer are essentially touching the bottom of the case. And they are all pinched by the PCB just the same! There is also a voltage switch mounted to the bottom of the case. No double square EU class II symbol exists on the case either.
 

Wombat

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#12
I know about class II compliance while using a metal case but it requires dual means of protection against shorts. No way this complies with that. The wiring to the transformer are essentially touching the bottom of the case. And they are all pinched by the PCB just the same! There is also a voltage switch mounted to the bottom of the case. No double square EU class II symbol exists on the case either.
Noting in your test reports the certification marks, or lack of, on products would be useful.
Also, what they mean.
:)
 

amirm

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#13
There are FCC and CE marks on the bottom. No UL. CE is self-certification. That means they can claim it but unless someone complains and EU investigates, violations can remain. A ton of no-name Chinese gear as a result has CE mark with no value. UL requires actual testing. As does FCC (for emissions).

CE is mandatory for import into EU. UL is not mandatory.

Given the common mode chokes and capacitors on the mains input board, I tend to believe that they have passed the FCC certification and CE components having to do with emissions. But I am doubtful that there is any safety certification or review.
 

Wombat

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#14
I
There are FCC and CE marks on the bottom. No UL. CE is self-certification. That means they can claim it but unless someone complains and EU investigates, violations can remain. A ton of no-name Chinese gear as a result has CE mark with no value. UL requires actual testing. As does FCC (for emissions).

CE is mandatory for import into EU. UL is not mandatory.

Given the common mode chokes and capacitors on the mains input board, I tend to believe that they have passed the FCC certification and CE components having to do with emissions. But I am doubtful that there is any safety certification or review.
I prefer EU or Australian standards given that we operate 240/250V supply in Oz.
 
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#16
Cannot quite tell how high the transformer is sitting relative to the case. Is the top of the transformer or screw near touching the top of the chassis?

Before reading this, I would have incorrectly guessed this DAC would have been built with higher quality standards. Most people, myself included would never think of opening up the case to inspect the internals. The issue with grounding the 3rd pin to the chassis is fairly simple fix. Same with the live wire touching the pcb. Can probably bend upwards or outwards slightly to avoid contact. The low quality capacitors is disappointing to see. I wouldn't want to go de-soldering and re-soldering better capacitors on a new dac. The capacitor that was cut off the board. lol. I wonder if all units are like that or just this one by chance.
 

amirm

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Cannot quite tell how high the transformer is sitting relative to the case. Is the top of the transformer or screw near touching the top of the chassis?
Yes!
 

Wombat

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#18
It could be supressing an audible top panel resonance/vibration due to the TX. You could peel it off and see what happens if time permits.
 

Sal1950

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#20
Hand soldering work is poor as is the horrible selection of cheap and unreliable capacitors that are bound to fail. Not acceptable at this price point.
What ya expect from 12 year old Chinese kids, they'll learn. :D
Used. Belongs to Sal. There is a good layer of dirt on it
Clean it up while your in there, OK? :)
Now Im not saying there is any resemblance to the sound of the Emotiva, however I was disappointed. Sounded noticeably lean.
As I mentioned in the other thread, sounds great mated to my Senn HD650s to me.
 
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