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Old 21st July 2011, 09:54 PM   #381
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Location: South Wales, U.K
Default Transformers & EMI shielding

Quote:
Originally Posted by Nosian View Post
What is a good shield between the tranny and the board? An aluminium plate cross the enclosure? or any better idea?
Ok, so someone mentioned the possible differences between E/I transformers, Torroids & R-core types and whether it's measurable. Prudence in design was mentioned too.
There are additional factors to include within the EI and R-core designs such as whether mu-metal EMI shielding (commonly utilised around AV speaker magnets) is incorporated or not. That may very well give rise to differing noise measurements / perceived sound quality.

To answer Noisan's previous question either Mu-metal or grounded copper screening plates could be incorporated between pwr supply section & dac board - I recall how some of Marantz/sony/philips top end Transport & DtoA models have compartments screened by copper plate & chassis

Also, if you do a search on this forum you'll find Peter Daniels experience of bonding a copper plate on top of & between dac i.c's and the grounding thereof

It's funny that this should arise in the postings now as this was the next mod I was looking to implement on my latest dual-dac kit (the CS4398 with VFD display)

-Andy-
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Old 22nd July 2011, 06:32 PM   #382
bismuth is offline bismuth  France
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Hi,

I just measured the dac with the ebay R-Core(2x9v+2x15V) and also with two 30VA R-Core (one is 2x9v, the other 2*12V), and there are small differences in the sub 1000Hz range. In red is the ebay R-core and in green the two 30VA R-cores. In solid the 2nd Harmonic Distortion and in dotted the third (in percentage) across the audio freq range.
At least it shows that transformer difference is measurable.

Caution with the ebay r-core to plug the 15V in phase beacause the wires for the two secondaries are the same color (yellow and brown).

Time for listening now...
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Old 22nd July 2011, 08:16 PM   #383
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Hallo

I am a total Neewbe, so sorry for asking a stupid question.
I have just soldered the ebay DAC but, have trouble finding out, how to connect to the transformer. The one of the two "power indputs" have 3 connections. I have a traffo whith 2x15Vac, i was planning to youse for this project. How do i connect the 4 wires from the traffo ? Please se my pictures.
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File Type: jpg 2.jpg (265.1 KB, 849 views)
File Type: jpg 3.jpg (385.2 KB, 828 views)
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Old 22nd July 2011, 08:20 PM   #384
syklab is offline syklab  Hong Kong
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Quote:
Originally Posted by bismuth View Post
Hi,

I just measured the dac with the ebay R-Core(2x9v+2x15V) and also with two 30VA R-Core (one is 2x9v, the other 2*12V), and there are small differences in the sub 1000Hz range. In red is the ebay R-core and in green the two 30VA R-cores. In solid the 2nd Harmonic Distortion and in dotted the third (in percentage) across the audio freq range.
At least it shows that transformer difference is measurable.

Caution with the ebay r-core to plug the 15V in phase beacause the wires for the two secondaries are the same color (yellow and brown).

Time for listening now...
How can you tell if they are in phase or not if they are both in the same color?
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Old 22nd July 2011, 08:56 PM   #385
bismuth is offline bismuth  France
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Quote:
Originally Posted by syklab View Post
How can you tell if they are in phase or not if they are both in the same color?
I used a two channel scope. I plug a yellow and a brown together for ground and the other yellow and brown to scope channels.

To be more precise, I plug the transformer to the dac with the wires that are in opposite phase.
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Old 22nd July 2011, 09:36 PM   #386
Trebla is offline Trebla  United Kingdom
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Silver84.

You have to search the web for the connection diagrams for your transformer.
I found this.

http://www.display.nl/components/com....12015.tek.jpg

You have twin secondaries.
The red and brown should be connected together as the lower drawing shows.
This becomes the 0 volts and should be connected to the centre terminal of the three way block.
The other two wires connect either side of it.

If you are only using one transformer, you have to join two solder dots underneath the board.
This connects the other bridge rectifier to the wires you have connected.
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Old 22nd July 2011, 09:47 PM   #387
bismuth is offline bismuth  France
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Quote:
Originally Posted by Silver84 View Post
Hallo

I am a total Neewbe, so sorry for asking a stupid question.
I have just soldered the ebay DAC but, have trouble finding out, how to connect to the transformer. The one of the two "power indputs" have 3 connections. I have a traffo whith 2x15Vac, i was planning to youse for this project. How do i connect the 4 wires from the traffo ? Please se my pictures.
You can try by putting together 'gn' and 'bn' wires for AC ground (in the center of the triple blue connector) and 'rt' wire to another connector, and 'bl' to the third connector. 'ge' and 'ge' must be plugged to the main 230V.

Note that if you did not the solder trick to join the two power rails on the board, you need another 9v transformer for the other 'double' connector.
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Old 22nd July 2011, 10:03 PM   #388
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Join Date: Jun 2011
Quote:
Originally Posted by Trebla View Post
Silver84.

You have to search the web for the connection diagrams for your transformer.
I found this.

http://www.display.nl/components/com....12015.tek.jpg

You have twin secondaries.
The red and brown should be connected together as the lower drawing shows.
This becomes the 0 volts and should be connected to the centre terminal of the three way block.
The other two wires connect either side of it.

If you are only using one transformer, you have to join two solder dots underneath the board.
This connects the other bridge rectifier to the wires you have connected.

That whas just what i needed, many thanks
I thinki will find another ´transformer for the two way block. That must be a better solution
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Old 23rd July 2011, 01:12 PM   #389
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Join Date: Jun 2011
bismuth --> Thanks to you to :-) I have just ordered another 9v traffo to the "2 way block" i

Btw. Funny thing. If i use a polhit to tjek the polarity (phase og 0 ) it light whith all the 4 wires. But if i take out the main power plug, and turn it 180* and put it back in, the polhit only lights up whith 2 of the 4 wires. This must be the correct way, to wire the transformer on the primary side ?
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Old 24th July 2011, 03:08 PM   #390
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Join Date: Mar 2001
Location: Brazil
Does anyone know who might be selling the AK4396 kit partly unassembled?

That is only having the SMD parts soldered on the pcb.

It seems more logical for me, if I will be upgrading many passive and active parts, not to have to desolder a part unnecessarily. The pcb might be damaged by doing so, particularly a problem with double sided pcbs.

Sometimes the only clean way to replace a part and not damage the pcb is clipping the part away. Then you just have to pull out a small piece of wire.

But as I said this could be solved by having a partly unassembled kit. OTOS I hate soldering SMD parts, particularly chips like the AK and CS chips. They were designed for machine soldering, not "human".
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