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Old 17th May 2007, 04:40 PM   #1771
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I received some enquiries with regards how to mount crystal oscillator in USB DAC: the pads went over footprint overlay and it's not clear what is pin #1. So I mark each board by engraving a small dot next to pin 1 (on the oscillator).

Below is the pic showing proper footprint.
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Old 17th May 2007, 04:44 PM   #1772
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The oscillator can be sourced from Mouser: http://www.mouser.com/search/refine....9-C3391-12.000
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Old 17th May 2007, 06:41 PM   #1773
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Default Re: Re: Transformer selection

Quote:
Originally posted by Peter Daniel

Presently, I choose 2 x 22V secondries on Plitron transformers I'm using. This produces close to 34V DC rails, with 2 x 24VAC secondaries the actual DC voltage would be 37V DC ( taking into account regulation margin and usually higher mains level).


Peter,

Thank you for your response.

Just one thing: how to calculate the regulated voltage?

I had thought that the rectified and smoothed voltage would be the RMS the peak to peak, (x0.707 IIRC), doubled up for + and - supplies (previous post).

That's where I got the rough estimate 1.4 x VAC, and the figure of 25V secondaries for 35V rails.

You say 2x24VAC => ~37V DC, but I make it 34VDC.

I'm sure you're right, but how do you do the calculation? What is a usual margin for 'usually higher mains level'. Mine (nominally 230V) reads *exactly* 230V.

Now that my LM3875 kit is in the post (thank you), I'm on the point of ordering the transformers. I was going to go for 2X25V, but now I'm not so sure...

Best wishes to all,
Steve
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Old 17th May 2007, 07:37 PM   #1774
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Transformers I'm using are rated for 115V and my mains are usually 120-123 V.

Also, you need to take into account regulation margin which may be another 6%.

That's why the actual voltage is usually higher than expected.
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Old 18th May 2007, 12:16 AM   #1775
gjash is offline gjash  Japan
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Peter, would there be any benefits to using a tentlabs oscillator? the package is different but I guess i could just solder the leads to the pads on your pcb....

Greg
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Old 18th May 2007, 01:26 AM   #1776
gjash is offline gjash  Japan
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Peter I'm wondering about MSR860s. e.g., d1-d4: it looks like on the s chematic and the pics you posted are at odds. looks like d1's anode, pin 3, should be connected to the transformer, but that doesn't look to be the case in the photo you posted earlier. Did anything change from earlier photos? thanks

Greg
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Old 18th May 2007, 01:58 AM   #1777
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Quote:
Originally posted by gjash
Peter, would there be any benefits to using a tentlabs oscillator? the package is different but I guess i could just solder the leads to the pads on your pcb....
There is enough space to fit Tent clock in top layer. Just drill 4 additional holes for the pins and wire them to the pads of the original oscillator. It's hard for me to comment on a difference, as I didn't try Tent clock here.


Quote:
Originally posted by gjash
Peter I'm wondering about MSR860s. e.g., d1-d4: it looks like on the s chematic and the pics you posted are at odds. looks like d1's anode, pin 3, should be connected to the transformer, but that doesn't look to be the case in the photo you posted earlier. Did anything change from earlier photos? thanks
The rectifier boards for LM3875 and LM4780 have diodes mounted in opposite way to match the opposite rail connection, see attached pic.
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File Type: jpg pcb.jpg (96.6 KB, 1560 views)
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Old 18th May 2007, 11:12 AM   #1778
Pocoyo is offline Pocoyo  Indonesia
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Default dac

Hii Peter

Do you research about dac too ?
are you sell it [dac] ?

just pcb, pcb+kits or full pcb ?
thank you peter
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Old 18th May 2007, 03:51 PM   #1779
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http://www.diyaudio.com/forums/showt...54#post1195254
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Old 18th May 2007, 04:49 PM   #1780
Pocoyo is offline Pocoyo  Indonesia
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Default sorry not real all post in here

hii Peter

sorry not to read all your post in this thread
im afraid i will sleep in front of my computer LCD
178 page ... wow

maybe you must talk to moderator to split this
posting into 3 thread

Oh yes you are very famous in Indonesia and
i know for sure you never come here yet

i will tell this dac to my friend, byee
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