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Old 18th December 2012, 12:29 PM   #151
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Quote:
Originally Posted by Ric Schultz View Post
You too Joe! Enjoy!
You bet, and the satisfaction you get back is a real bonus too. It seems I get these beautiful bottles of wine quite regularly, somebody gave me a Pinot Noir (from New Zealand) today. I like Pinots.

I'm just about to read what you've done to the 105, thanks. Read what you did earlier on the 103.

Cheers, Joe R.
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Old 18th December 2012, 01:46 PM   #152
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Joe Rasmussen

thank you for your patience and having time to explain what you wanted to say by saying use SAW

due to other principles of operation are involved noise has other distribution figure or even different nature all that leads to more dramatic sound advance compared to just to use expensive especially low jitter oscillator 'cause as you researched jitter doesn't always matter
of course, I'll try SAW type, thank you for sharing your experience
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Old 18th December 2012, 08:20 PM   #153
Coris is offline Coris  Norway
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Originally Posted by Joe Rasmussen View Post
Can you or Coris confirm my impression, reading between the lines, that Oppo has left left DC on the outputs, as DC bias to be seen by those caps? That may not be a bad idea as caps generally do better with some DC bias. But, in which case you have to find a way to remove the DC offset and you can't just get rid of the caps, as some seem to have suggested.

My own solution will be the same as the '95 which is DC coupled. The question is whether to sacrifice the headphone amp - I can disable all the I/V ICs, I can run 4x paralleled using jumpers. As these will each see a common 3R3 to ground-plane near DAC (reference point where things cancel), picking up anything stray has to be about as minimal as it gets. I will get same performance as '95 I suspect.

Still would like further confirmation that we are definitely back to 27MHz as was the usual standard in the past with Mediatek/Oppo.

I may possible get my first '105 this coming week.

Cheers, Joe R.
It is very possible to get DC offset 0,000 with right components and right design. The resistors involved in analogue stage after the DAC are crucial. Not at least the right opamps... In production process (producing thousands of PCBs) this is just not possible... Or it may cost the final product a fortune...
I think is not very easy to work around (jumping) the output of the ESS9018 in 105. One do not know what design it may be under the chip or in the internal layers of the PCB. The solution is to lift up all the output pins of the DAC and do another connections. This it may be very risky and involve an very big amount of precise work. I`m not at this moment very sure what procedure is to be followed... In the 95 model the (stereo) outputs were already coupled 4+4...
This mod it seems to me for the moment a very difficult task... It still to be analysed this mod I suppose, to be found it the right way(s).
But at last one may not be very obsess about coupling all together the outputs channels. It may work well as Oppo have designed/assigned the outputs of the DAC chip, if another mods are do it right in another stages... We will see...
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Old 18th December 2012, 09:21 PM   #154
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The stock 105 has no offset voltage before the output coupling cap.....I just measured my unit and all outputs are 5mv or under. The circuit is just the usual: IV converter for each phase and then another opamp to sum. When you sum you get rid of the DC offset (relative to the matching of the four resistors in the summing stage). This is how the 95 was and they used NO coupling caps. You can remove the caps, if you like. The balanced outputs use a differential driver that has reference to ground so has no voltage on their outputs as well. However, it is better to get rid of the summing opamp altogether and use a better IV converter then straight out through a coupling cap...way better. When you sum you are just adding the sound of another opamp and its passive components used (resistors, caps, solder joints). Less is better!

As far as summing more of the outputs together....well, the jury is out on that one. Some find that using them single is best. The traces for all the outputs are usable and if you want you can put them all together....without any surgery or removing of parts. There are many, many more important ways to improve the sound than the possible paralleling of the outputs. Please don't get hung up on one area.

Last edited by Ric Schultz; 18th December 2012 at 09:33 PM.
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Old 18th December 2012, 09:52 PM   #155
Coris is offline Coris  Norway
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Thanks for infos. 5mV is an very good offset. I still wonder why they use separation caps in this model, if it were just fine as it were (DC coupling) in 95 model...
Else I fully agree: are many ways to improve the player before thinking to sum the output channels. No, I`m not hang on this area. It ware my thoughts, answering/commenting the Joe`s post...

I found it at Digikey an 54 Mhz oscillator (PN 1253-1054-1-ND) which is specified as "Type SO (SAW)"... I can not see in the data sheet something about SAW type... I think I will give it a try anyway to this and another similar one 27Mhz.

Last edited by Coris; 18th December 2012 at 10:01 PM.
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Old 19th December 2012, 07:55 PM   #156
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Originally Posted by Joe Rasmussen View Post
Why am I saying this? Because what we did made no difference to the jitter spec and we heard the same improvement with all kinds of clocks/oscillators, even cheap ones - and it allowed us to clearly hear differences too.
Thanks for this, Joe. I just read the related material on your web site. Please correct me if I'm wrong, but it occurs to me that (following your "jitter is analogue" image) that jitter frequency would be (as with analogue waves) inversely proportional to 'wavelength'--in the time domain, presumably the number of clock cycles affected per 'cycle' of jitter (with jitter amplitude being the amount of phase shift per clock cycle). So very low frequency jitter (also called 'wander,' I believe) would, if this model holds, be that which shifts the signal across the largest number of clock cycles. If this is true, then it makes perfect sense that, other things being equal, the lower the frequency of jitter, the more distortion of the signal it would cause. A 1-Hz jitter component would affect, for instance, 44.1 thousand samples of a Red Book CD signal. A two-Hz jitter component would affect 22.05 thousand, etc. The additive effect of several low-frequency jitter components (even allowing for statistical cancelling out of some the huge sum of phase shifts) could, even if jitter amplitude were held constant across the jitter frequency spectrum, result in a potential for dramatic timing errors in signal reconstruction at all audio frequencies. Whereas higher-frequency jitter, affecting comparatively few clock cycles, would be more likely to inflect harmonics/timbre higher in the audio band, and their additive effects would be smaller.

It would be interesting, if adequately sensitive test and clock-perturbing equipment exists, to do listening tests on the effects of injecting different very narrow frequency bands of jitter on the same audio signal (clocked by something like the Rubidium clock), followed by the testing the effects of "stacking" several of those narrow bands of jitter, particularly at relatively low frequencies.

In any case, such a model would seem to confirm both the efficacy of ultra-low noise power supply design and construction (to power the digital circuitry) using known techniques, as well as of the discovery and implementation of clocks with optimum inherent stability (thus synchronous oscillators--rather than PLL--based on SAW devices would be candidates?). Given successful execution in these two areas, then one could look at minimizing sources of random rather than periodic jitter, such as thermal noise, etc.

I'd welcome comments on all the above--I am no specialist in this field and I could be way off base, or this could all be old hat to those in the know, but if it is, I don't think its impact on audiophile gear design has really hit home yet.

Thanks--this my first post, so please set any flamethrowers to "low."
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Old 19th December 2012, 08:41 PM   #157
couch is offline couch  United States
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PS to the above: I do realize that the actual clocks involved are running in the MHz range, so that a 1-Hz jitter/wander component would actually affect potentially millions of clock cycles, but it would still affect the number of signal samples corresponding to the sampling rate . . . .
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Old 20th December 2012, 01:58 AM   #158
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Hi Coris,
XLR outputs are balanced as you know, so it might be 2 channels per phase, the other outputs are single ended and would be only 2 channels as there is only 1 phase.
This is how it is in the 95?

What do you think?
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Old 20th December 2012, 08:16 AM   #159
Coris is offline Coris  Norway
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Hi Chris
In 95 the output channels of stereo stage DAC it were coupled together 4+4 with common I/V stage and the resulting signal it were amplified accordingly and distributed to XLR and SE outputs.
In the BDP-105's stereo board design, the 4 pairs of DACs in the ESS9018 DAC are allocated as: 1 pair for the RCA outputs, 1 pair for the XLR outputs, and 2 pairs stacked for the headphone amplifier. It seems that every type output it have its own I/V stage.

I looks like the headphone stage benefit most of this design... But let`s not be very obsess of this new stacking of DAC in the last model... It may be good enough. I did not took yet my self an close look on this aspect. Very soon...

Last edited by Coris; 20th December 2012 at 08:31 AM.
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Old 20th December 2012, 10:59 PM   #160
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Has anyone here directly compared a very low phase noise 100MHz XO such as
Crystek CCHD-575 to equivalent SAW 100MHz oscillator with same power
supplies etc?

If so, what was the sonic difference.
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