ezDAC v.1.5 Builders Thread - diyAudio
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Old 13th March 2009, 03:24 PM   #1
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Default ezDAC v.1.5 Builders Thread

Post your pics, thoughts, comments, questions here...
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Old 14th March 2009, 08:31 PM   #2
M-chen is offline M-chen  Germany
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Default just finished

Hi all,

here we go:

ezDAC V1.5 in my Sony XA-50es.
Powered by two Audiocom Super Regulators for 3,3V and 5V with its own transformer/rectifier unit, made of super-fast recovery diodes and 10000uF load capacitor.
The oscillator is a Tentlabs XO with a maximum jitter of 3ps rms.
The inputs are 16 bit right justified format taken directly from the Sony chip (CXD2545Q). That is the reason for the absence of an input receiver on the ezDAC PCB.
The analog outputs are directly taken from the PCM1794 to a LC-Audio Zapfilter 2. So the I/V conversion and all the analog stuff is done there. Discrete parts are the way to go, not opamps (just kidding)!

As you can see in the attached file this modified ezDAC does not need to many parts anymore. That saves some time for the build of course.
Finally one word about the most important, the sound:

Just WOW!

If you have any questions left about the modifications, just ask.

Greets,

Martin
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Old 14th March 2009, 11:37 PM   #3
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Martin, how do you power the XO? Is it 3.3V?
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Old 15th March 2009, 10:02 AM   #4
M-chen is offline M-chen  Germany
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The XO does not care about the voltage to much.
It accepts either 3,3V or 5V. So in this case it is 3,3V of course.

Greets,

Martin
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Old 15th March 2009, 10:41 PM   #5
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Default Broken Wire

The problem I was having with no output was down to a broken wire on the digital input. Fixed now and sounding great. Albeit quiet.
I'm running the output directly into a headphone amp and to listen at normal volume requires the amp to be turned right up. It looks like the output of the DAC is designed to be about the output level of a CD player about 150mV I would imagine. What is the actual output and can I increase this to line level, so I can directly feed some power amps?

Secondly to add a couple of extra inputs, would I just add extra sockets going to, say, a three way switch and then to the input for the board?

Thanks for a great sounding design.
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Old 15th March 2009, 11:03 PM   #6
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Default Re: Broken Wire

Quote:
Originally posted by stonedowner
The problem I was having with no output was down to a broken wire on the digital input. Fixed now and sounding great. Albeit quiet.
I'm running the output directly into a headphone amp and to listen at normal volume requires the amp to be turned right up. It looks like the output of the DAC is designed to be about the output level of a CD player about 150mV I would imagine. What is the actual output and can I increase this to line level, so I can directly feed some power amps?

Secondly to add a couple of extra inputs, would I just add extra sockets going to, say, a three way switch and then to the input for the board?

Thanks for a great sounding design.

Glad to hear it's working (hopefully, you can attach some pics).

Line level is about 2V, and that should be roughly what you're getting if you used the R values given in the BOM.

As to the other questions, I would recommend making your switch occur before the DAC input. That way, each signal can go through the transformer.
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Old 15th March 2009, 11:28 PM   #7
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Could you confirm the component values. In the standard BOM R27 and 28 are 3K where as in the fancy BOM they are 1.5K. R25 and 26 are the same in both at 27R as are R25 and 26 at 100R.
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Old 15th March 2009, 11:39 PM   #8
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If I remember the rationale (it's been a while), PCM1794 ("fancy") has about twice the output current of PCM1798 (standard), so I adjusted the resistor values to account for that.
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Old 16th March 2009, 09:14 AM   #9
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What resistors should I change to increase the gain of the op-amps?
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Old 16th March 2009, 11:37 AM   #10
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The ones you mentioned, R27, R28, plus R33, R34. If you're using PCM1798, try raising those resistors to 3K.
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