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Modding epic desk dock

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By Top Nurse, Senior Member on 5th March 2011, 07:13 AM
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3rd April 2012, 03:45 AM |#41  
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Lightbulb Long time coming...
I know I teased about this a month ago but I'm finally done and it works.

The short story. I had a couple friends help me build an amp circuit that could run off the usb power, while still charging the phone, and vastly improves the audio as well as almost eliminates the hiss/static. All while managing to cram it into the existing dock. The End.


The long story. I had tasked a friend with building a simple amp circuit with minimal components. He likes challenges so after a couple weeks he responded with a simple circuit that did exactly what I asked. After tweaking it to work off of our phones usb ouput and adding a small circuit to try to eliminate any noise from the usb power we finally had success and the audio was way better. It sounded great.

The last challenge was to try to fit it into the dock along with the existing board and to tie into that board without causing any problems. After a week or two of tinkering with the design I finally came up with something I thought would fit and start to build it out. After a few burned fingers and redo's I finished it tonight and after closing the dock back up everything still worked and sounded great.

I plan to put up a schematic of what we used incase somebody else wants to attempt this. I took some pictures of the putting it all together and the finished product.

I wish this was a little easier to build and install but in the end it turned out to be more difficult to fit in the dock than I originally thought.

Description of the pictures:
IMG_4566.jpg - This is the test I did to connect the amp board to the existing dock board to ensure everything worked on the dock. Because of the way the dock is put together you have to put the amp board in the dock and route the wires out and connect them to the dock board and then shove that whole mess back into the dock.

IMG_4567.jpg - This is another shot of the test build.

IMG_4568.jpg - Not the best picture of the amp board. You can see the LM386 chips (amps) as well as the output caps and the power filter cap and transistor on the south side of the board.

IMG_4569.jpg - A bit better picture. You can see the transistor better on the power filter circuit.

IMG_4570.jpg - This shows where I tapped into the dock board. I disconnected the D+ and D- wires from the phone connector and wired those directly to my input wires. I then put the outputs from the two amps to the D+ and D- locations on the phone jacks. Also you can see where I tapped into the 5V and the Ground (orange and white/orange wires).

IMG_4571.jpg - This shows a side profile of the cap side of the amp board.

IMG_4572.jpg - This shows how I put the board in the dock. Notice how I had to compensate for the screw pole inbetween the gold and blue caps. Also notice how I trimmed every last piece of the circuit board that I could off to make it fit in the dock... and it just barely fit. It took a little convincing but it does fit. I also covered the metal base and under my amp board with electrical tape otherwise things wouldn't have lasted very long.

IMG_4573.jpg - This shows the connected amp board wires to the dock board. Since I tied the D+ and D- directly to my amp board input lines I just black tapped those instead of making the connections on the board because then there would have been interferance between the on dock board traces and my new amp board.

IMG_4574.jpg - This shows my completed dock charging my phone while playing music. Also note the blue LED still works on the dock as well.

I do plan to put together a parts list and a circuit diagram and post them here. Hopefully that doesn't take me a month to put together.

A note about the quality. My testing and best guessing is that this amp circuit eliminates >90% of the hissing/static noise that existed when the charging usb was connected while playing music. The LM386 chip is a pretty standard and powerful amp chip and the tinny/no bass sound was vastly improved to the point where I think it sounds the same as the phone's headphone jack.

I'm not an audiophile so if you build this out and it doesn't sound perfect I've warned you. BUT it is definetly way more listenable than the plain dock.

I'll post more info in the next few days.
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3rd April 2012, 04:13 AM |#42  
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Quote:
Originally Posted by bmasephol

I know I teased about this a month ago but I'm finally done and it works.

The short story. I had a couple friends help me build an amp circuit that could run off the usb power, while still charging the phone, and vastly improves the audio as well as almost eliminates the hiss/static. All while managing to cram it into the existing dock. The End.


The long story.I plan to put up a schematic of what we used incase somebody else wants to attempt this.

Yes please do. I was just starting on the same thing.

Sent from the Drivers Seat of my Suby txting and Driving doing 100MPH+ in a school zone! Ha.
3rd April 2012, 01:28 PM |#43  
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Nice and thanks for sharing. Would love to see the schematic & parts list.
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4th April 2012, 04:40 AM |#44  
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Quote:
Originally Posted by bmasephol

...I'm finally done and it works.

Would you post a comparative spectrogram to show the differences?
Use a high quality wav (rip a CD track or something) and zoom in on the spectrogram view (instead of waveform) in Audacity.
Play the same wav from your phone headphone jack and record to computer line in from Audacity.
Then play the wav again from the dock and record again.
You will end up with 3 tracks that you can align and zoom to capture a single screenshot showing a comparison.

Please post a picture of the bottom of the amp or a schematic (if you want to share it.)

Congrats on taking the project to this point. This might not be a marketable design improvement due to the age of the Epic... but it looks like the market has responded to the need for alternatives for newer devices. Check out this Galaxy Note dock for $1.50 wholesale (retailing $10-$13) http://www.alibaba.com/product-gs/53...r_Samsung.html
4th April 2012, 03:14 PM |#45  
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I never though of recording on the computer to compare the headphone jack and the output of the dock. I wish I would have done it with the dock prior to modifying it.

Anyways, I built the dock at home and tested it there. Brought it to work yesterday and had terrible noise when I tried to listen to music. Did some testing with different brands of chargers here at work and it got no better. Took it home last night and everything was back to sounding fine.

I'm working with a couple friends to try to figure out what at work might be causing all the interference.

I will say I work in an old building where we have cubes as far as you can see and tons of computer equipment running. I might have to redesign or rework the power filter or figure out a way to put something on the ground to reduce noise on the headphones.

I'm going to work on a part list and circuit diagram tomorrow, my wife has surgery so I'll be sitting around all day with her at home.
30th June 2012, 06:10 AM |#46  
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I'm kind of steamed after buying this stupid dock and not being able to connect the phone to my computer Guess it's my fault for not researching it more thoroughly.

If I rewired this to just be a USB passthrough (skipping the board completely) could I hook up the LED in the front somehow still?
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