MayDus, PCM2706/CS4398 USB DAC w Transformer output. - Page 2 - diyAudio
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Old 25th April 2012, 06:45 PM   #11
Mayday is offline Mayday  Sweden
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According to the postalservice tracking I should get the dac-board tomorrow
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Old 26th April 2012, 04:42 PM   #12
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Got this today, will desolder the smd resistors on the dac-outputs and solder wires to the edcor XSM 10K/10K transformers I'm waiting for.
May have buy a new box for it too.

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Old 27th April 2012, 07:42 AM   #13
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The Edcor XSM's was shipped on the 22:nd, I'm hoping I'll get them on Monday
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Old 27th April 2012, 03:16 PM   #14
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The marked four resistors are to be removed and the solderpads used as solderpoints for the wires to the edcor xsm 10k/10k output transformers.

Click the image to open in full size.

I will also remove the rca-connectors. I have no use for them and should I one day want to use opamp instead of transformers, I can easily solder wires to better rca-connectors.
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Old 2nd May 2012, 02:02 PM   #15
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According to tracking the Edcor XSM's should arrive at my door before 16:00 tomorrow
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Old 3rd May 2012, 07:53 AM   #16
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Today I'll get the Edcor transformers and hopefully the enclosure. I've ordered the same one that I use for my B1 preamp.

The plan, if there's enough room, is to put the MayDus in the same enclosure as my Lehmann clone headphone amp since I'll only use it for that.
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Old 3rd May 2012, 10:35 AM   #17
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Got everything I need now, just waiting for the holecutted I've ordered to arrive before I start this build.

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Old 3rd May 2012, 03:04 PM   #18
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What do you plan to drive with the transformer outputs?

Since the Op Amp you bypass performs the analog LPF, how will you implement it?
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Old 3rd May 2012, 03:22 PM   #19
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If needed, I'll put a capacitor between the primaries. CT will be left floating.
This is not all that goes into connecting the transformers, but I'm writing from my phone now and have no access to the schematic.
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Old 3rd May 2012, 04:56 PM   #20
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The schematics I've seen on ebay for this design do not show pins M1,2,3 connected. However, the manual states they must be connected to gnd or Vcc. I found one PWB with a close up that shows them connected to ground, which is what I suspect for all of them. This puts the DAC in (M0-1) Left-Justified, up to 24-bit data and (M2-3) Single-Speed without de-Emphasis (32 to 50KHZ sample rates.

I believe that this will configure the device for Single-Speed (fast) Stopband Rejection per figure 20 on page 41.

Your dynamic range will be slightly degraded by not having the analog butterworth filter.

However, the output without a filter looks like it is better than 100dB. I suspect the filter gives another 20dB as they claim 120dB dynamic range.

You may lose some micro-detail and imaging without the filter.

It might be interesting to see if I can drive my sound card from the unbuffered output of the DAC to see how it looks on AudioTester.
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