New PCM1794A Kit – Balanced Mode Update – Good to Fantastic Sound! - Page 18 - diyAudio
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Old 28th April 2012, 12:05 PM   #171
spencer is offline spencer  Hong Kong
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As the designer of FDA-1B kit, I would like to provide some comments here:

The fact is that layout of the FDA-1B is the most important to the final result of the same circuit. Accumulation of the proper layout is very important to prevent any issue but some designs will only be accumulation of issues to give worsen result.

Few points that I want to highlight again:
1. Careful layout of every sections of the DAC.
2. Use symmetric design as far as possible for the full balance output.
3. Align the digital bus timing for all 4 I2S signals as well as left and right channel timing for minimum phase error.
4. Choose the best WM8804 digital receiver chip.
5. Choose the regulators that give most optimized sound.

I cannot say the current design FDA-1B is perfect but I would say it progress a lot since the FDA-1 layout from 1.5 years ago. I always design everything in a single board unless there is no choice because I can control the consistence of the connections to ensure consistence of result. FDA-1 is a Single End design from day one and it is not optimized to work in full balance mode. Thus FDA-1 is not able to reach a higher level of performance.

Thank you for all your support in FDA-1 and I am sure there will be more fun and enjoyment for those who decide to try FDA-1B.
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Old 28th April 2012, 01:20 PM   #172
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Today I started my FDA-1 soldering!
Now I have no pleasure to solder any further!
That was not good timing for me
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Old 28th April 2012, 05:35 PM   #173
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@florentino:

believe me the FDA-1 is a really cool project! It sounds great!! I use it every day

br recorder
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Old 28th April 2012, 11:42 PM   #174
TC Goh is offline TC Goh  Hong Kong
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I second that! Despite the improvements of the FDA-1B, the FDA-1 is still very capable. You should definitely go for it...

TC

Quote:
Originally Posted by recorder View Post
@florentino:

believe me the FDA-1 is a really cool project! It sounds great!! I use it every day

br recorder

Last edited by TC Goh; 28th April 2012 at 11:51 PM.
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Old 29th April 2012, 12:04 PM   #175
akira is offline akira  France
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Dear Spencer,
Just to be clear ... Wenn I was wondering how the b version could be so much better than the a, I was not putting any doubt in the quality of your products. I am the happy owner of the D1V33 and the FDA1a version.
Cheers

Akira
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Old 30th April 2012, 05:27 AM   #176
spencer is offline spencer  Hong Kong
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Akira,

In my comment number 4, the WM8804 just make the DAC sound almost perfect. I can hardly tell the difference between XMOS --> I2S input and 16bit/44.1k SPDIF input now. Refer to the jitter measurement on the manual, the jitter rejection by WM8804 is really excellent. Thus I have no more urgency to switch to XMOS (USB) input as the SPDIF input sound same good!

No 3 is also very important as there are now two DAC chips and the I2S signal must reach the two chips at the same timing to avoid any phase error for left and right channels. This can be easily heard in the sound stage and 3D improvement.

For other improvement, refer to my previous comments.

For a 100 point scale of improvement, the WM8804 will contribute 50% and no. 3 contributes another 30% and the rest 20% by others.
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Old 30th April 2012, 08:25 AM   #177
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Quote:
Originally Posted by recorder View Post
@florentino:

believe me the FDA-1 is a really cool project! It sounds great!! I use it every day

br recorder
Thank´s recorder!
ok I will finish it!

but one question to have the best performance!
What is the best connection between PC and FDA-1!?
I thought of the M2Tech HiFace USB interface?
Or is optically better?
thanks for helping
florentino
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Old 30th April 2012, 01:30 PM   #178
TC Goh is offline TC Goh  Hong Kong
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Looks like Spencer has put the revision history of the FDA-1B on his site fetaudio.com. I feel he has taken meticulous steps in arriving at the final production version.

TC
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Old 2nd May 2012, 11:40 AM   #179
UMarcus is offline UMarcus  Germany
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Quote:
Originally Posted by spencer View Post
As the designer of FDA-1B kit, I would like to provide some comments here:

The fact is that layout of the FDA-1B is the most important to the final result of the same circuit. Accumulation of the proper layout is very important to prevent any issue but some designs will only be accumulation of issues to give worsen result.

Few points that I want to highlight again:
1. Careful layout of every sections of the DAC.
2. Use symmetric design as far as possible for the full balance output.
3. Align the digital bus timing for all 4 I2S signals as well as left and right channel timing for minimum phase error.
4. Choose the best WM8804 digital receiver chip.
5. Choose the regulators that give most optimized sound.

I cannot say the current design FDA-1B is perfect but I would say it progress a lot since the FDA-1 layout from 1.5 years ago. I always design everything in a single board unless there is no choice because I can control the consistence of the connections to ensure consistence of result. FDA-1 is a Single End design from day one and it is not optimized to work in full balance mode. Thus FDA-1 is not able to reach a higher level of performance.

Thank you for all your support in FDA-1 and I am sure there will be more fun and enjoyment for those who decide to try FDA-1B.
Hi Spencer,
many thanks for your comments and information about the new design.

One additional question :
Refere to the pictures it seems no Vishay Dale RN / CMF Resistors populated anymore as used in many places ( I/V and output stage) of Kit A. Did you had done some tests with resistors, how was the result ?

Many thanks,
regards
Marcus
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Old 5th May 2012, 11:28 AM   #180
spencer is offline spencer  Hong Kong
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UMarcus,

I do not want to comment too much on part selection but please read this very good article by Audio Precision in below link. Create a account if you cannot download it.

AP High Performance Audio Analyzer & Audio Test Instruments : Home
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