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Old 31st August 2011, 04:01 PM   #101
Alex_twn is offline Alex_twn  Taiwan
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Join Date: Jul 2009

I am bringing back this thread up after a tweak I operated on my FDA-1 that turns then into an Airplay DAC.
It works now wirelessly with devices like MAC, PC, iPad, iPhone, Apple TV, ... but also with original coaxial, optical and balanced inputs and best of all the sound quality is improved

I hacked an airport express N by bonding out the I2S bus and directly connecting it to the two PCM1974A from the FDA-1.
In the end the Marvell main controller is driving directly the Burr Brown DACs, the system becoming fully sunchronous and the CS8416 is completely bypassed removing in the same time the possible jitter problems due to I2S signal extraction from AES/EBU frames.

I posted photos of Airport hacked + installation in the FDA-1 here:

Modification Airport Express (Zardoz, Rosita, Airstream...) - Page 25 - Sources
DAC FDA-1 (PCM1794A Spencer) - Page 11 - TDG

I can comment / give additional details if some of you are interested.

Again audio quality is getting a step further, mainly precision & details are even better, instruments sounds so real, bass are a bit improved as well.

It is a good and not too difficult upgrade if you have a good soldering iron and good eyes

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Old 31st August 2011, 05:29 PM   #102
qusp is offline qusp  Australia
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Location: Brisbane, Australia
thanks for the pics, i hve been thinking about the airport i2s mod. i do think that you could improve performance by making a couple of changes. firstly, thats a massively long, unshielded and not even twisted pair cable for the i2s connection, plus several connectors that are not at all suited to high speed signals. i fear your jitter will be very bad. so if you must have it this long, you should use belden shielded low capacitance networking cable or similar and pair each signal with a ground wire, delete the connectors if possible. but you really should try to make it shorter. you could also use a quality ribbon cable with every second wire as ground if you arent already doing that

Last edited by qusp; 31st August 2011 at 05:34 PM.
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Old 2nd September 2011, 09:36 AM   #103
clin36 is offline clin36
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Join Date: Aug 2011
hi All,

Have been following this thread with great interest.

Ordered the balanced kit from Spencer today. He has been very helpful in answering some of my initial questions. Looking forward to receiving the kit from him.

Embarrassed to say, especially in DIY forum, but I ordered the kit assembled (parts mounted on board), because of personal situation I just don't have the time to work on DIY project such as this. Hoping to be very satisfied with it (sonically), but if not then will look into tweaking.

Will update you all once I get my unit. Will hook up to a Marantz CM1040 (slim-line series) CD/mini-disc player.

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Old 4th December 2011, 09:20 PM   #104
ENSen is offline ENSen  Sweden
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Join Date: Dec 2010
I bought the balanced kit from spencer a while ago. This weekend I finally had time to finish it. Have listened to it for a couple of hours today and I am very impressed. The sound is clean and dynamic with very good resolution. Instruments sounds like real instrument and not synthetic ones which is the case with many DACs

When I have time I will compare it to my commercial DAC that uses the PCM1792 chip which is almost the same as PCM1794.

The support from Spencer is superb and the kit is very nice with all components sorted in plastic bags that are clearly marked. I highly recommend this kit.
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Old 12th December 2011, 10:28 AM   #105
spencer is offline spencer  Singapore
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Reversion 6 Manual updated in my website:

FDA-1 PCM1794A DAC Kit Revision 6 Manual

Thank you for all the support.
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Old 16th January 2012, 07:06 PM   #106
arupg is offline arupg  Latvia
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Join Date: Dec 2005
Location: Riga
Hello Gentlemen :

I've read each one of your posts all the way to #105 and must say that I've so far YET to see & go thru a "Thread" on this Forum with so much enthusiasm bubbling all over ... Its Just awesome !! (reminds me of the CarlosFM days ...) haha !!

Indeed - Spencer has pulled a BIG one here ...

TC's inputs were most illuminating & must say I'm kinda itching to get my hands on a dual-set board and get going ...

However, I am mainly a classical music buff (though I do jazz & some rock / pop once in a while), I wish to ask what's your opinion of this FDA for classical ? I like my bass stretching low with articulation (as I listen to a lot of Organ material) and am kinda fussy on the top end too - as l like it mellow yet open to the sky ... Mids - as usual clean, clear & spacious ...

Inputs will be most appreciated.

And ahh, well done Spencer! You've got a real winner here ...



Last edited by arupg; 16th January 2012 at 07:12 PM. Reason: typos
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Old 17th January 2012, 09:39 AM   #107
Nomdi is offline Nomdi  France
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Join Date: Sep 2011
sorry that's not the good thread ..

Last edited by Nomdi; 17th January 2012 at 09:53 AM. Reason: thread error
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Old 17th January 2012, 09:49 AM   #108
TC Goh is offline TC Goh  Hong Kong
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Join Date: Jan 2010
Location: Hong Kong
Hi Arup

Welcome to the band wagon! I was one of the early adopters and have been impressed with the DAC ever since. With the new lower pricing (…. grrrrrr…..), it is even more tempting. With this, I would go for the full balanced version. You will find that the improvements from SE will be well worth the $$$ and effort. You will be able to cut the assembly time by doing both boards at one go – saves you from having to locate component positions twice! Also, you get twice the fun at once … now how can you resist that? Ha ha.

I would suggest you listen to the vanilla version (Silmic BP and all) and then progress from there. After that, the fun continues …. You can consider upgrading the 7805 regulators to the L4941BV. This increases the punch of the music, which is a good thing in my all tube system.

Next … the really fun part … output coupling caps and bypass caps!! I tried various output caps and bypass but the best combination, in my opinion, is still ‘bare’!! OCL! The sound is more dynamic, musical and lifelike, all with a wider and deeper soundstage. I think this set up has the least amount of colouration. However, word of caution …. READ THE MANUAL!!!

Of course, whatever set up you end up with needs to match your system so I guess there is no one formula that works.

Oh, do get a good and sturdy case too. Just the eye candy would be well worth it.

The latest ‘upgrade’ I did was to shield the TXs with a grounded aluminum plate. I can’t tell if this improves the fidelity but I am sure it prevented those EMF gremlins from attacking the DAC.

Do please keep us updated as to your progress/decisions.

Oh.. Welcome to the world of flux smoke, sleep deprivation and blurry vision...

Have fun….

Best wishes

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Old 17th January 2012, 09:52 AM   #109
TC Goh is offline TC Goh  Hong Kong
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Location: Hong Kong
Hi Nomdi

I think everything you need can be found here ...


Best wishes

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Old 23rd January 2012, 09:57 PM   #110
zibra is offline zibra
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Join Date: Nov 2011
Anyone of you tried other regulators than those 2 mentioned at documentation? Im thinking of replacing it by some kind of discrete regulator like supertedddyreg, DEXA etc.
Any hint? Im really curious for resyult and which one to choose? Also do you believe it will change sound for both Cirrus and PCM? Anyone tested it?...
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