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Old 6th July 2013, 08:09 PM   #591
Coris is offline Coris  Norway
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Quote:
Originally Posted by Seiyoung View Post
Hi Coris!

Have been reading your post with much enthusiasm. Powering the clock circuit with battery is very interesting. Very low internal resistance of a battery will surely give good result. BTW, have you ever considered using super capacitor (or ultra capacitor) in the range of some 10 to 50 Farad instead of battery? Super cap is usually rated for 2,7 Volt, so can be connected serial to have 5.4V rating. For 3.3V application, it has enough margin.
Super cap has uncertainty for audio use but I hear some good result.
Yes, I have considered very large capacities, too. I just bought 2 of such caps, but I have not succeeded yet to experiment this way. I think to use such large capacity (but not as high as teens F) caps for decoupling the power rails on the chip power input. I have a enough long list of experiments, and researches on different things in the field, but (of course) not enough time...

In my concept, there is a difference when using battery and very large capacities. The battery can provide very long time the power, comparing to caps, even though that caps are of very large capacity. The caps need to be "filled up" with power all the time... They do not generate as batteries... So there may be an regulator or power source before that caps. The battery is charged once and it can provide the power (quite constant on these lithium types) for very long time (on low/reasonable current use).
In this case of ES9018 DAC it may be an idea to power it from battery completely. but an quite elaborated design it may be in place to rich this task. I have in mind to take a closer look at this concept, but I do not know yet when...
Using battery to power oscillators (on few teens mA) it works just wonderful and it is very simple. I still wonder how in fact these oscillators are made inside, because they can tolerate large power supply variations (extremely slow rate in case of a battery, when discharging), without no any impact on the outputted frequency, and for the rest of the DAC system. I have used (experimental on Oppo 95) a such powered oscillator with a full charged battery, and let it work (for more than two weeks, many hour use every day) until it were stop by itself (discharged battery under the oscillator Vcc low limit). I could never notice an variation in the quality of the sound outputted. You know, when it stopped to work that oscillator, I was just listening something on the player. The sound it were just high end, and suddenly it stop everything. I was very surprised because I could not notice before it stopped working any malfunction of the DAC, bad sound and so on, which it could indicate that the battery it may be too low. Every thing it were working wonderful and suddenly stopped.
I have done this experiment with two different DAC chip types/systems. The same exceptional result.
In this case of an 3,3V oscillator there is about a Vcc lowering variation of 0,6V! It only works just fine... But when is about a reasonable use of the DAC system, and then charging the battery at once when the system is off, then the variation of tension at the oscillator power input, is in the worst case, no more than 0,2V...
All of us knows about how much work and research is done to find the lowest noise regulator solution. Ultra low noise regulators chips are created, sophisticated shunt regulators designs is used, and anyway it is not enough to get the cleanest power for very special circuits as DAC and clocks. Put a battery in place and it is just done. The difference of the sound out of a such powered clock system is only huge.

Last edited by Coris; 6th July 2013 at 08:18 PM.
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Old 11th July 2013, 01:12 AM   #592
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I am incredibly busy right now, but I have sketched out a circuit that I will post as soon as possible. I could post it now, but then not have the time for the necessary follow-ups.

I also want to actually try it on my own '105.

It will be based on a transconductance circuit/device SOIC package. Where the existing Oppo circuit needs 3 SOIC in total for two channels, this will actually only use two, as the summing of the phases takes place at the very input and no after two separate (and currently asymmetrical I/V converters that then needs another opamp to sum it together. Also, the filtering is largely passive (passive components are rather hard to force into slew - and it takes the 'heat' off the active circuitry) up to three poles (two is enough) that are buffered separately.

I will try post on Sunday.

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Old 11th July 2013, 01:22 AM   #593
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Quote:
Originally Posted by Seiyoung View Post
Super cap is usually rated for 2,7 Volt, so can be connected serial to have 5.4V rating.
Don't think that is a good idea unless to really know what you are doing. They have large amounts of dialectic absorption and they may differ from one sample to the next. So when discharged and then turned 'on' the voltage across one may see above 2.7V even if only 3.3V is fed to the series. You may try two resistors that may help to prevent the near full voltage appear across one of them. But you will need to calculate the current. Then there is the turn-on current of these caps. it can overload small SMD 3.3V regs. Also these caps, when turned 'on' first time, especially if they have been on the shelf. needs the voltage come up gradually. Not saying you can't use them, but need to be aware it is not simple.

Cheers, Joe
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Old 11th July 2013, 10:12 AM   #594
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Joe, I can see you do have working knowledge concerning super caps. I tried to use it to my car amp and found it somewhat strange and finally took it out. For dynamic load change, they are very slow (to be charged) and cause some odd things. I just wonder how it work for the static load like clock osc. Yes, many things to be considered, for sure. Thanks for your insightful tips!
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Old 11th July 2013, 02:50 PM   #595
Coris is offline Coris  Norway
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To be honest, I do not think that using caps in many Farad range to drive oscillators is a special nice/useful idea. Not even to substitute a battery to power a circuit.
Large capacity caps it may have a clue and positive impact in a device functioning when is to be used for decoupling. When about powering a device then one may chose power sources... A cap is not a power source, but an power accumulator/buffer.
The large capacities caps used for cars amplifiers, are actually huge decoupling capacities. These improve the low end of the audio frequency spectre for that car amplifiers and provide enormous instant (peaks) currents needed for that sort of high power amplifiers (special in low frequencies ranges). Such instant power needed at once by those type amplifiers, can not be provided by the car battery. That because are used so large caps as buffers in between battery and amplifier. Special circuits needed to start up charge it and for protection is a big challenge in the field. Everything become too much complicated and for doubtfully results when about using such for oscillators...
BTW, my personal opinion is that car amplifiers do not deliver at all high fidelity sound, but high power low frequencies to bump the bass elements in a very noisy environment, as a functioning car is...

At least we may back to the thread main discussion line: Oppo 105 player...

Last edited by Coris; 11th July 2013 at 03:06 PM.
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Old 16th July 2013, 05:05 PM   #596
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So other than the SAW oscillator and the Modwright mod, has anyone
found any other mods that affect this player for the better? Thanks to Coris for sharing his research in the oscillator department.
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Old 18th July 2013, 07:53 AM   #597
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Joe,

Do you know what the approximate impedance is that the stock Oppo 105 DAC circuit drives? I'm assuming that it is setup to drive an Op-amp which is presenting a "virtual ground" and is running as an active I/V convertor, correct?

I'm curious if in all of your experimenting if you ever removed all of the loading so that the ESS9018 was running purely in "voltage mode" instead of "current mode"? I didn't realize that it was even possible to run this DAC in "voltage mode" myself until about a week ago when I happened to try it on DIY ESS9018 based DAC kit which I just acquired. I know that this chip is supposed to measure better when run in co-called "current mode", rather than voltage mode. But my ears don't agree, and actually prefer the sound in voltage mode (I just sounds far more dynamic and "alive"), even though in "current mode" it is running a passive I/V arrangement somewhat similar to what you have described doing.

Anyways, I was just curious about what kinds of I/V configurations you have experimented with and what it was that made you go in exactly the opposite direction?

Last edited by TarnishedEars; 18th July 2013 at 08:02 AM.
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Old 18th July 2013, 08:04 AM   #598
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Quote:
Originally Posted by TarnishedEars View Post
Joe,

Do you know what the approximate impedance is that the stock Oppo 105 DAC circuit drives? I'm assuming that it is setup to drive an Op-amp which is presenting a "virtual ground" and is running as an active I/V convertor, correct?

... I didn't realize that it was even possible to run this DAC in "voltage mode" myself until about a week ago... and actually prefer the sound in voltage mode (I just sounds far more dynamic and "alive"), even though in "current mode" it is running a passive I/V arrangement somewhat similar to what you have described doing.

Anyways, I was just curious what kinds of I/V configurations you have experimented with and what it was that made you go in exactly the opposite direction?
It may well sound better in Voltage mode because less has gone wrong and if you no longer use opamps to get a virtual earth, which is what the stock player does. That virtual earth sits at 1.65V (that is why it is virtual) and relies on feedback to achieve the effect.

But if you pull the output to ground and cause 2.1mA of offset current per phase (each 781R) and use small value 'current sense' resistors of a few Ohm, then use a very high quality amplifier (preferably without feedback IMO), then I can assure you it sounds much better than just Voltage mode. You can't do that with any other DAC that has an offset voltage - in which case you are likely to cause damage, but the Sabre DAC is different because it had a defined known output impedance that in effect is equavalent to a series resistor, so we know exactly how it behaves when we terminated at or near REAL earth conditions.

I am shortly about to post a schematic... so wait a little while and you will see a detailed example.

Cheers, Joe
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Last edited by Joe Rasmussen; 18th July 2013 at 08:09 AM.
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Old 18th July 2013, 09:45 AM   #599
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Default Modding OPPO 103

Hi to all

these are some photos of my modded 103.
I use this player only as a digital transport, the analogue stage was dismout.

- First of all i installed a linear PSU from Jea Hong, but all caps has been changed. I installed 2 20.000müF and 2 33.000müF from Mundorf Lytic, which are quite big and made space problems. Each of them is bypassed with small wima mkp caps. Some small Rifa Pme247 were added.
The small values were changed to oscon SEPC smd with the lowest ESR known to mankind. Use only the 16v version and not more than 470müF.
Then somthing really important, the main fuse. This was changed to Padis Rhodium.

- Next thing was the smd caps on the digital board, all has been changed to the oscon SEPC 16v 470müF.

- Both clocks were changed to NewclassD / Dexas new small size Dclock Neutrino launched in may this year. Both have an own linear PSU. My experience is that the best clock without its own LPSU is nothing.

- Every PSU has its own mini power conditioner in kind of a staggered delta filter between line-neutral / line-earth and neutral-earth.
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Old 18th July 2013, 10:29 AM   #600
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PART ONE

EXECISE: HOW TO IMPROVE FUTURE BDP-115

OTA: Operational Transconductance Amplifier

Click the image to open in full size.

This is an exercise in how the next generation Sabre DAC fitted Oppo Player may get a significant jump in audio performance (particularly unbalanced stereo, although a balanced version can also be shown).

Manufacturing to a price is an art in itself - and business. Often products are criticised, sometimes fairly and often unfairly, that they could easily be made to sound better.

But what seems simple is often not.

For example, it is useless to suggest an alternative unless the active device is fully surface mount SOIC package - and this will be.

To me it is clear that the Oppo's post-DAC circuit presents a unique challenge, and if we want to progress, we must use something that takes us beyond the usual opamp (operational amplifier) configuration. Opamps are used because they are cost-effective and comfortable solution.

The alternative must also be cost effective, so we must keep an eye on component availability and cost. I believe this can be done, especially as the solution is an OTA based SOIC made by a major American manufacturer and this device looks to be available for a significant time into the future. Discrete active devices are almost certainly out of the question. Examine the way that the Oppos are made and you have to fit in with that - or you are out.

So top of the list: The active device has to be an 8-pin SOIC. It must be in current production and by a major IC manufacturer (and the one we will be be using doesn't come any bigger).

We know why manufacturers use opamps, they are predictable. But the use of opamps are problematic as they are feedback devices and that is not ideal, especially not inside a chassis with a significant amount of high energy HF, and not just radiating but also on the very signal coming out of the DAC. In fact, people like Charlie Hansen of Ayre has identified this as a significant contributor towards "digital sound" - and it is not difficult to figure out why. As the rise time of non-content specific noise is anywhere near the limit of the feedback to keep up, then in subtle ways (and sometimes in horrific ways) the open-loop performance of the opamp can be exposed. There is also the 90 degree feedback error caused by the internal compensator capacitor used in pretty much all opamps.

The logical answer is to use no feedback - but of course that is where the challenge starts. We need to think outside the box.

There is a certain class of opamps that can be used without feedback.

And at least one is a SOIC. I am not at this point disclose it identity, but simply state that it does exist.

Please look at the proposed schematic above. Let me say that a more complex version of this works, because I am using it. It is not available as SOIC, so the device we have in mind is similar and yet different.

But this less complex version will perform very differently to opamps - and sound far more musical, with more true instrumental colours where opamps tends to grey things out and sound thinner. The bass is also predicted to be well above the norm.

Over the next week or two, I am going to experiment with this SOIC.

In the next part, we will discuss the features and possible values of the above schematic.


.
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Last edited by Joe Rasmussen; 18th July 2013 at 10:31 AM.
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