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DDDAC 1543 MKII distortion on analog output
DDDAC 1543 MKII distortion on analog output
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Old 22nd May 2008, 07:15 AM   #11
ecdesigns is offline ecdesigns  Netherlands
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Now that I know what to listen to, clicks are audible for sure. I find it difficult to accept it as normal.
If clicks are audible with sinewaves, they are also audible with music fragments containing sinewaves.


I can verify that DDDACs clocking method indeed improves transparency by effectively blocking source jitter, so the concept is valid.


The clicks are caused by the CS8414 receiver buffer under-run / overflow. This problem is caused by slave clock mode (both BCK and WS are inputs), in combination with source and master clock running (slightly) out of sync.

If the source clock runs slightly slower than the master clock, there won't be enough samples to fill the receiver buffer, so samples need to be repeated, if this condition lasts too long, too many samples are repeated sequentially, and audible clicks occur.

If the source clock runs slightly faster than the master clock, there are too many samples, and the receiver buffer overflows, now samples have to be dropped, if this condition lasts too long, too many samples are dropped sequentially, and audible clicks occur.

So the problem with clicks can simply be solved by avoiding receiver buffer over / under runs, in practice this means matching / syncing the master clock with the source clock.

One possible option is to use an adjustable master clock (+/- 100ppm), and match the master clock frequency as closely to the source clock as possible. This should reduce / eliminate audible clicks. Tentlabs offers 2.8224 MHz low-jitter VCXOs (Voltage Controlled Crystal Oscillators). The oscillator frequency of these VCXOs can be varied slightly (approx. +/- 100ppm) by varying the DC control voltage between 0 and 5V. The problem with this method is that the adjustment procedure must be repeated for each source, and oscillator drift (master / source) may require re-adjustment.

Best way to solve this problem is using the VCXO with an appropriate PLL configuration, in order to lock the master clock to the source clock.
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Old 22nd May 2008, 07:45 AM   #12
zdr is offline zdr  Belgium
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It makes perfect sense. I did not get too much into the subject so far as this is my first stab at DAC part of DIY, but now makes me wonder how other reclocked designs deal with this phenomenon? I don't think it's by having a screwdriver next to DAC chassis.

For me, sacrifying clean and distortion-free sound for the sake of slight improvement in imaging and transparency is not acceptable. I find myself now more trying to catch artifacts, rather than listening to music.

So far, a very unhappy owner of DDDAC.
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Old 23rd May 2008, 09:30 AM   #13
SM7UYJ is offline SM7UYJ  Sweden
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From the description, it sounds like I have had a similar problem with one off my TDA1543 DACs.

My problem was solved by resoldering the DAC-stack (18x) !

/R
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Old 23rd May 2008, 11:39 AM   #14
zdr is offline zdr  Belgium
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Which problem exactly did you have, parasite harmonics or clicks? I have already resoldered and reseated the whole tower couple days ago, so unlikely to be the cause of the problem. I even replaced 2 TDA1543 just in case.

See also post above from designer claiming that this is normal behaviour due to reclocking, due to difference in incoming SPDIF Fs and reclocked Fs, which makes perfect sense to me.

Can anyone with working SPDIF DDDAC MKII confirm that there are no clicks with 15KHz or 10KHz sine wave? I really hope it's me who did something wrong here.
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Old 23rd May 2008, 11:55 AM   #15
zdr is offline zdr  Belgium
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And yes, I almost forgot - I got the same result with one TDA1543 only, so tower is out of the question for sure.

To summarize, there are two issues here, with CD4000's SPDIF as a source:

1) Low frequency clicks, with any freq sine wave. If I run 15KHz for example, which will be barely audible for me, I hear clicks only. Theory that this is audible in sine waves only and not in music, is kind of ridiculous, and I am not amongst those who can hear difference between cables. If I can hear it, anybody can.

2) Parasite harmonics in audible spectrum as depicted above. They are all over the place. Simple comparison with default oversampled output of Marantz CD4000, puts DDDAC down hard in this respect.

I would very much like to hear from other owners of DDDAC MKII with SPDIF receiver.
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Old 23rd May 2008, 11:59 AM   #16
SM7UYJ is offline SM7UYJ  Sweden
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As I remember, I had both harmonics and "clicks"!

My DAC had no reclocking, so the cause for the "clicks" was most likely current related!

Hope you find the cause (and cure) !

/R
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Old 3rd August 2008, 11:09 AM   #17
benoitmabille is offline benoitmabille  Belgium
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Default in my case...

I had same issue ('clicks' on SPDIF input). Was caused by low quality chassis female cinch plug, wired to the SPDIF input. The plug was of really low quality (I choose it because of plastic body for isolation from chassis). Once it was changed to a better one --> no more clicks !
Hope it helps.
Benoit
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