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Old 22nd August 2011, 03:23 PM   #3931
Ryssen is offline Ryssen  Sweden
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Now I have removed the ferrites,so Im one step closer to heaven..
There are those who say the ferrites shold be left there or you shoud add ferites.I dont know I dont hear any differebce on them........
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Old 23rd August 2011, 10:51 AM   #3932
gsa is offline gsa  United Kingdom
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Hi Ryssen, I must point out that removing the FB's is probably a waste of time if you dont seperate the supply rails. Its probably why you dont hear any difference .

If you do seperate the supplies there is an FB on the 8421 board that chokes the sound.

Talking of the 8421 board I will need to add yet another PSU to run at 2.5v as the 8421 chip requires 2 power rails. This will bring the PSU count to 7 excl opamp supply, the same as sheldons board.

The work never ends....
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Old 23rd August 2011, 12:59 PM   #3933
Ryssen is offline Ryssen  Sweden
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Quote:
The work never ends....
Do you mean that every PSU needs its own winding (transformer)
Or is a preregulator enough?
Do you mean that the 8421 VD and VL needs separate PSU?
I a separate regulator for the XO now.
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Old 23rd August 2011, 05:04 PM   #3934
gsa is offline gsa  United Kingdom
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Currently the upsampling board has a single 3.3v regulator situated on the board, its fed from a 5V rail. On the standard board the 5V rail is shared by VA on cs4398 DAC. There is a FB on the upsampling board which is used to isolate the supply, its shared remember.

On my modified board I have cut the track and provided the upsampling board with a dedicated supply at 3.3V. I also removed the FB and associated input caps. Take a look at the pictures in my earlier post.

I have 3 transformers which gives me 6 seperate windings each with its own regulated PSU. [overkill, but makes a difference]

Now here is the issue:

The 8421 needs 5.0V/3.3V for VL and 2.5V for VD and I have 3.3V on both, in an ideal world I would run VL at 5V and use a seperate regulator at 3.3V for the clock with another at 2.5V for VD. In total I need 3 regulated supplies, I need to add another 2. I will get round to it at some point. I will share a couple of the transormer windings to do this by adding fully rectified PSU.
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Old 23rd August 2011, 05:23 PM   #3935
gsa is offline gsa  United Kingdom
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I buy these power supplies, fully rectified variable LM317, I change the smoothing caps to 4700uf.

Voltage Regulator Kit, AC/DC in, DC out, Based on LM317 | eBay


I have included a photograph of where to look for the shared track its the middle one between the tracks. If you lift the DAC out and follow these tracks you will see how the supplies are all mixed up.

I cant express the difference it makes to seperate them, even if you dont add seperate transformer windings.
Attached Images
File Type: jpg IMAG0121.jpg (827.6 KB, 594 views)
File Type: jpg IMAG0124.jpg (385.5 KB, 534 views)
File Type: jpg IMAG0133.jpg (954.2 KB, 536 views)
File Type: jpg lm317.jpg (51.4 KB, 520 views)

Last edited by gsa; 23rd August 2011 at 05:27 PM.
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Old 23rd August 2011, 09:59 PM   #3936
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Quote:
Originally Posted by gsa View Post
The 8421 needs 5.0V/3.3V for VL and 2.5V for VD and I have 3.3V on both, in an ideal world I would run VL at 5V and use a seperate regulator at 3.3V for the clock with another at 2.5V for VD. In total I need 3 regulated supplies, I need to add another 2. I will get round to it at some point. I will share a couple of the transormer windings to do this by adding fully rectified PSU.
I pointed out the problem with the design back many pages ago, that they were running the 2.5V VD at 3.3 volts (really really close to the absolute maximum rating). Apparently the chips can handle it, but it's not a good idea. Back toward the beginning of this thread there were a bunch of folks who were toasting 8421's and I found that issue with the design. I haven't heard of anyone having issues lately, so apparently the 3.3 volt regulator on the newer ASRC board does the trick.


Sheldon
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Old 23rd August 2011, 10:24 PM   #3937
gsa is offline gsa  United Kingdom
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Yup I read the same stuff earlier in the thread, initially I assumed my board was newer and the issue was completely fixed. I initially thought the on-board reg was 2.5V and maybe the rail voltage was 3.3V.

This is not the case, I wonder if there is a potential divider dropping the voltage? Just not sure. I will get to the bottom of it at some point.

The whole board is a mess.

Its working out to be a great tutorial, learning all the way.

Finally I am getting what I would consider as "high fidelity" sound. Its starting to remind me of my past equipment.
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Old 26th August 2011, 06:49 PM   #3938
data is offline data  Australia
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Quote:
Originally Posted by gsa View Post
I buy these power supplies, fully rectified variable LM317, I change the smoothing caps to 4700uf.

Voltage Regulator Kit, AC/DC in, DC out, Based on LM317 | eBay


I have included a photograph of where to look for the shared track its the middle one between the tracks. If you lift the DAC out and follow these tracks you will see how the supplies are all mixed up.

I cant express the difference it makes to seperate them, even if you dont add seperate transformer windings.
Can you point out to me what each of the wires in the first pic are, I take it the red ones are coming from the ebay regs? supplying X.Xv?

What about the other two under that go under the DAC daughter board?

Thanks

I'm only now looking at doing more than the transformer output.
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Old 27th August 2011, 02:22 PM   #3939
gsa is offline gsa  United Kingdom
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Hi Data, the wires inder thr DAC board are the differential outputs, I removed the pins and soldered wires directly into the smurf board.

I hope that the attached pictures are a little mor informative.
Attached Images
File Type: jpg modpower.JPG (548.5 KB, 469 views)
File Type: jpg CS8416Mods.JPG (373.7 KB, 221 views)
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Old 27th August 2011, 02:27 PM   #3940
data is offline data  Australia
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Yes, thank you

That helps heaps.
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