2008 7月-12月 第1項課程召集 - (1) 夏季 DAC 原理和製作班 (10月11日繼續組裝)

Dear KK,

I just bank in deposit for the DAC course. I also would like to reserve the DAC1955PRO for integrating with the CDPRO2M which I enrolled earlier. So that my CD player has a concrete architect to start with.

I think AD1955 in balance architecture is the most appropriate platform for me. Closed to my current Meridian G08 CDP. Detail system architecture (like I2S clock derived from DAC and feed into CDPROs) will discuss with you later. This makes my project exciting.

Thanks in advance.

Autumnleafcat.

So I would consider two chassis solution. Not too bad anyway.

gene, good idea...

How about the I2S clock output module from DAC1955 board to CDPRO2.

I've listened to Meridian G08.2 in Central Hifi Galaxy. The New 8.2 has stunning details while maintains suitable bodyline texture of instrunments. Bass and high frequency extremes are widely extended. I think I have to try hard on the DAC1955/CDPRO2 combo to beat this newly release machine on both musicality and fidelity.

Thanks admin and KK for this bonus class on DAC design !!

It is better to learn more details as soon as possible and plan for next step of our own DAC design. If every things are already assemblied but a possible upgrade is taught afterwards, then it may be too late / too difficult to implement the upgrade change on our DAC design.

So I would prefer bonus class being held on 11 SEPT. Or post teaching material topics of bonus class in advance and let us prepare our questions well before attending the class. Time is too tight in class.

Thanks KK for your outline of the bonus class. This helps a lot.

You may quote the maths and equatoins lightly for those who can handle.  Simulation is a good idea since we can get LTSpice for free.

Hi KK sir,

I am using default plan since I want to look for my dream component set myself. However it is really extremely hard to find all the components I desired in the market. Therefore I asked you and william for the upgrade plan late on yesterday. But William replied both upgrade plan A and B were not complete right now (some missing parts in both plans) because I was too late to request.

"Both heads cannot reach the shores", "兩頭唔到岸", 好慘! 頭髮白晒!

I think I cannot complete soldering my dac before Monday. 仲撲緊零件

BUT I would come on SEPT 15 to look at you testing for other c chings. I think I have no problem testing mine at home since in fact I have built several dac before: (3623, 8412, 8420, 5843, pcm63pk, 1704.......) If not many issues, I could handle the test at home.

話晒都係紅褲仔出身麻 !

If possible I would bring a small bottle to take some cleaning fluid home to wash the PCB myself. I know the washing procedure.

Theory of flux band to reduce leakage flux in power transfromer:

We firmly wind one turn of copper foil (with its width slightly smaller than bobbin width) on the outside of the transformer core and perfectly short-circuited the foil. Since this one turn is not in the main flux path of the core (you can imagine the difference in winding geometry of primary, secondary and this copper-foil windings), it will not induce emf from flux inside the core because the resultant flux is zero for this one turn, so it will not affect normal tansformer operation.

Only the leakage flux from the transformer core will induce emf on this one turn. Since this single-turn copper foil has almost perfect zero impedance from both dc and ac sense (super low DC resistance and ultra low inductance, that's why use copper foil instead of wire), the short-circuited induced current in this copper foil has no power loss. By Lenz law, a magnetic field is generated from this single-turn to oppose the leakage field and thus giving us the leakage cancellation.

Flux band concept:

practical example of power transformer incorporating flux band.

Looking inside flux band construction:

If ching wants to further reduce the leakage flux, one should use core belt wearing around the core. Core belt is made of highly magnetic conductive material to absorb stray field. However Core belt usually a custom built part to suit particular core. Therefore it is seldom use except certain product. You can cover the transformer by a steel/mu-metal can. But mu-metal does not sell in small quantity.

But flux band is only for reducing leakage magnetic flux from core. Certainly not 100%. For those who want to supress noise from power line, the transformer should add a faraday shield between primary and secondary winding. By connecting the faraday shield to ground. High frequency noise will capacitively couple to ground. The noise suppression is also not 100%. Adding a line filter can help a lot.

Transformer is not simple.

not yet finished!

Many thanks to KK sir.

I interest in listening sound of plan C ...

dir9001 can give 192k lock status indication to mcu in dac1955pro?

PLL RC value need to adjust for 192?