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Old 26th January 2013, 11:04 AM   #61
EUVL is offline EUVL  Europe
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A few people sent PMs asking for Bill of Materials for the circuits.

Firstly I have, as an exception, already posted component values in the schematics.
But they should be treated as provisional, and will only be finalised after we have completed all build and tests ourselves.
This will help us and you, to avoid confusions due to multiple revisions.
From our experience from the F5X and the Joachim Gerhard projects, we have also decided only to publish final schematics and BoM at our own website.
This will allow us full flexibility for Version control and editing.

So I can only ask you to kindly bear with us for now.
When we are ready to publish them, we shall put up announcements here.


Thank you for your interest,
Patrick
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Old 15th February 2013, 10:15 AM   #62
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At last some further progress to show. Tests to follow.

Space on top is reserved for the HAGS which is still waiting for PRP resistors as well as FETs matching.


Patrick
Attached Images
File Type: jpg 130215 DAO Proto1 a.JPG (106.5 KB, 958 views)
File Type: jpg 130215 DAO Proto1 b.JPG (86.7 KB, 790 views)
File Type: jpg 130215 DAO Proto1 c.JPG (90.6 KB, 771 views)
File Type: jpg 130215 DAO Proto1 d.JPG (122.4 KB, 766 views)
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Old 15th February 2013, 10:46 AM   #63
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Really nice Patrick!
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Old 15th February 2013, 02:27 PM   #64
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Not yet quite finished.
Still work in progress........




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Old 16th February 2013, 02:16 PM   #65
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Some test results :

Current configuration is DAO standard, bias 195mA.
10kHz square wave with 56R load is perfect without any overshoot.
Gain is 0.876, in line with expectation (Load = 56R, Zout = 7.8R, of which 6.8R is pure resistive.).
DC offset 4mV.

Also as expected some load is required for stability.
For headphones with high impedance, especially at HF, a Zobel of 27R 10nF will ensure perfect response.

Next steps would be to add TCs and HAGS module.


Patrick

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Attached Images
File Type: jpg 130216 DAO Proto 1 Test a.JPG (121.1 KB, 733 views)
File Type: jpg 130216 DAO Proto 1 Test b.JPG (174.7 KB, 357 views)
File Type: png 130216 DAO Proto 1 10kHz Sq Wave.png (32.8 KB, 313 views)
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Old 16th February 2013, 10:00 PM   #66
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I like your work!
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Old 16th February 2013, 10:01 PM   #67
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Thank you.


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Old 4th March 2013, 11:13 AM   #68
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Slow but gradual progress.
Here the first HAGS prototypes.


Patrick
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File Type: jpg 130304 HAGS Proto 1&2 Top s.jpg (228.7 KB, 452 views)
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Old 1st April 2013, 10:46 AM   #69
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Took a bit longer than I wanted, but HAGS is finally tested.

Without any trimming, initial DC was 160mV.
After one trimming resistor (calculated value), DC was down to less than 4mV at steady state.
Cold start value was about 15mV, but this settles to near zero after 3 minutes.
Bear in mind that the DAO following the HAGS is unity gain, and 10mV is 1.5W for a 65R headphone, I do not consider servo necessary.

Attached also square wave response for 10kHz and 100kHz, as well as frequency response to 2MHz.
-3dB is at about 1MHz. So performance meets expectation.
(Green is input, cyan output.)




Patrick
Attached Images
File Type: png 130401 HAGS Proto2 10kHz Sq.png (21.9 KB, 328 views)
File Type: png 130401 HAGS Proto2 100kHz Sq.png (25.9 KB, 137 views)
File Type: png 130401 HAGS Proto2 Freq Resp.png (21.1 KB, 144 views)
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Old 1st April 2013, 11:12 AM   #70
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Very nice performance. Indeed, the offset is small enough not to need a servo, as long as it does not drift, and I expect you have paid your usual attention to the thermal design so that it does not drift.
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