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View Poll Results: Have an AES-21?
Yes - still works fine 0 0%
Yes - broken like yours need a replacement 1 100.00%
Yes - still works but interested in performance upgrade / better jitter reduction 0 0%
No - just answering this poll for fun 0 0%
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Old 6th February 2014, 06:21 PM   #1
nacc18 is offline nacc18  United States
diyAudio Member
Join Date: Feb 2006
Location: michigan
Default Ultra Analog AES-21 Upgrade / Replacement Project

Hello Everyone,

I believe I have searched forums long enough to re-start this topic (everything I found is dead and at least 3 years old)...

I am on my second AES-21 in my Classe DAC-1 and it's starting to fail again. I know many others with Parasound DAC 2000s or other Ultra Analog DACs have the same pain with their AES-21s (or 20s).

So it's about time I (or maybe someone already has?) made a plug-and-play replacement with new parts, maybe a quality crystal re-clocker, that for whatever reason doesn't die so easily. I'm thinking CS8416 with tolerant filter -> some nice crystal-based PLL with tight filter. This will go (at least in my Classe) straight out to the PMD-100 HDCD filter so I should have some room to work with on the module for good power supply, decap, etc.

In summary the idea here is to put a good RELIABLE receiver and 21-st century clock (whatever will fit!) in these great old DACs with minimal fuss.

If anyone knows anything or has any recommendations it would be appreciated. Or if you've already done the same thing a starting point would be a time-saver. I'll make a PCB that matches the AES-21 pinout so if anyone is REALLY interested let me know if you'd like a finished one once I get around to parts (several months from now...)

Thanks in advance everyone
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Old 7th March 2014, 12:04 PM   #2
Korrah is offline Korrah  Malaysia
diyAudio Member
Join Date: Feb 2006
Location: Canberra
Out of curiosity, how does the AES-21 "fail"? Does it just stop locking onto the SPDIF signal?
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Old 7th March 2014, 12:45 PM   #3
nacc18 is offline nacc18  United States
diyAudio Member
Join Date: Feb 2006
Location: michigan
Hi Korrah,

I have experienced two types of failures, one of which a friend also with an AES-21 shares.

1) My DAC (classe DAC 1) worked perfectly for years until finally zero lock could be achieved on anything. incoming frequency showed 32 kHz (lowest f display on front panel) and lock failure light came on, no sound, dead. I swapped out the AES-21 and it worked perfectly again on power-up.

2) My second AES-21 is having seemingly random pauses in sound, as if dropping samples. Sometimes it's like a CD skipping, sometimes I get 40 minutes of perfect before failure, sometimes just 1 minute between a slight hiccup. This behavior a friend of mine also experiences although much less often and he has a different DAC than mine (parasound 2000).

Both of us have clock-upgraded CD players so our incoming SPDIF streams are much cleaner than normal - the cirrus part in the AES 21 (i think it was an 8412 they used) might be failing or maybe the XO they use to re-clock afterward is (pretty sure from pictures I've found that there's a second PLL in the AES-21 that re-clocks).

I will have a schematic for the new AES-21 module very soon. I've explored a few different options and will upload once I finish with the details.
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