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Old 6th July 2012, 09:54 AM   #41
erin is offline erin  Australia
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Samwha has been around for quite a few years. Found in tv sets and VCR. I wouldn't consider them a high quality audio cap.
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Old 6th July 2012, 11:24 AM   #42
bcmbob is offline bcmbob  United States
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I haven't double checked yet but it appears everything else came in the first shipment.

I did get a couple early responses from good.feedback - he told me regular emails through his yahoo address sometimes end up in his trash folder The messages that got through were on the eBay response system.

alkasar, I just bought (Sunday) a second JC-2 preamp kit and an R-core trani for use with DACs from mindshadow. A world of difference in the entire transaction. Already received USPS tracking info.

I have the 1K resistors but the 33 ohm and some 150s are the closest my stash has to offer. Does anyone think those are close enough, or is ordering the exact value the best option?
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Old 6th July 2012, 07:49 PM   #43
alkasar is offline alkasar  France
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Quote:
Originally Posted by dhalbakken View Post
I'm quite sure that only one dual op-amp is being used in the new version instead of one dual plus two singles. Maybe something like this:

Click the image to open in full size.
DAC5 still has 3 slots for dual opamps, it probably still has the low pass filter.

DAC6 output stage however looks similar to the above schematic... actually very very similar. Even part numbers are the same. You have some magic to get schematics Dave
DAC6 has a variable resistor instead of fixed R27 or R34, to adjust offset. If I am not wrong, this is only to unbalance.
I'll plug DAC6 tomorrow and run some listening tests.
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Old 7th July 2012, 04:20 PM   #44
TheGimp is offline TheGimp  United States
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alkasar, you can do a frequency sweep with an oscilloscope and frequency generator.

You just have to plot the test points manually on graph paper.

Get some Log-Log grapah paper.

Set the test tone to 10Hz at -10dB and measure the output. Plot on paper.
Set the test tone to 20Hz at -10dB and measure the output. Plot on paper.
Set the test tone to 50Hz at -10dB and measure the output. Plot on paper.
Set the test tone to 100Hz at -10dB and measure the output. Plot on paper.
Set the test tone to 200Hz at -10dB and measure the output. Plot on paper.
Set the test tone to 500Hz at -10dB and measure the output. Plot on paper.

Continue through 20KHz.

If RightMark won't let you specify a frequency and amplitude, try AudioTester. I've usd it for several years and iirc the demo version will allow you to set these, but you can't save any plots. Since you are manually generating the plot it won't matter.

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Old 7th July 2012, 05:49 PM   #45
alkasar is offline alkasar  France
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thanks for the hint.
I once had a try with audiotester and didn't like it. Can't remember why. Nevermind : Rightmark RMAA does both : multitone and swept sine. It's not shown in the html report but it is visible in the application.

I have done some listening tests with DAC6. It plays very nicely. I have the feeling that there are more details in the high frequecies than my other dac (AD1955) but hard to tell as I can not do an A/B test.

Here are some measurements. All measurements are done on a Laptop running XP with an USB EMU0204 used as input device.

RMAA measurements
DAC6 measures OK but but nothing fantasitc compared to the EMU0204.

Summary comparison
Click the image to open in full size.

full report
RightMark Audio Analyzer test: comparison

square wave
I also measured some sinewave and squarewave response, eventhough I have no clue how to interprete results

For this, I use Visual Analyser software. A very powerful and very confusing tool... kind of a virtual scope on pc.

green wave is left channel, with 1kHz square wave
red wave is Right channel, with 1kHz sine wave

Input device is EMU0204 configured at 48kHz (bandwith 24kHz) or 96kHz (bandwith 48kHz).
Output device is either DAC6 or EMU0204 (loopback)

here are the screenshots. Obviously result depends on bandwith.

dac6 with 24kHz bandwidth
Click the image to open in full size.

dac6 with 48kHz bandwidth
Click the image to open in full size.

EMU0204 in loopback, 48kHz bandwidth
Click the image to open in full size.

hope this helps,
Al
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Old 7th July 2012, 05:56 PM   #46
alkasar is offline alkasar  France
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this is also interesting : spectrum of the 1kHz square wave with DAC6
we can see plenty of odd harmonics

Click the image to open in full size.
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Old 7th July 2012, 06:19 PM   #47
bcmbob is offline bcmbob  United States
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Made good progress on my build. Just have to order a few parts and hope to be up and running by mid week. Going to order exact values.
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File Type: jpg 20120707_133604.jpg (105.4 KB, 187 views)
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Old 8th July 2012, 12:33 PM   #48
bcmbob is offline bcmbob  United States
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To all - I read back through all the pages here and only found a few comments on the actual sound quality of this DAC. The test/graphs being highly significant, don't address what we are all most interested in - what it sounds like.

Can/will anyone post some subjective impressions/comparisons of what they hear with this unit?

Thanks
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Old 13th July 2012, 11:19 PM   #49
bcmbob is offline bcmbob  United States
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Got lights but no sound.

Unfortunately, I started out with a problem. As always I did first power up using a dim bulb tester which indicated a short somewhere. I found a solder bridge on one capacitor (A). With that fixed, there was no fault detected by the bulb but still no light on the power LED. Reversed the polarity of that and the other two LEDs and got power indication.

The USB LED lights when that cable is connected, and the "SP" LED lights up when S/PDIF RCA from computer is attached.

DC offset reads 0.00 mV for right ch and 6.3 mV on left. There are no hot spots detected by an IR thermometer or by placing my hand over the board.

On USB - no sound or hum can be heard. Driven by the RCA, a very faint, scratchy non-musical ghost impression of what's being played can be detected through the speakers.

Opamps at "C" call for OPA624 and are correct. Those at "B" call for OPA2604 as marked on the PCB, but one OP275-G-811-G4428 and one OP275-G-903-G6404 came with the kit.

I didn't get any documentation, and my assumption that the red toggle was a power switch was proven incorrect. In the down position the SP LED is active and off when lever is up. It must be a mode switch for the tenor module???

As always, I'm open to all help and suggestions.

P.S. My eBay supplier still hasn't un-disappeared himself but I will shoot this post off to the other vendor in hopes he may offer some assistance.
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File Type: jpg 20120713_174816.jpg (130.8 KB, 153 views)
File Type: jpg 20120713_174821.jpg (170.3 KB, 137 views)
File Type: jpg Marks.JPG (432.0 KB, 187 views)
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Last edited by bcmbob; 13th July 2012 at 11:27 PM.
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Old 14th July 2012, 04:44 AM   #50
repeet is offline repeet  Australia
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The switch changes the spidf input from optical to coax
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