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Old 12th March 2013, 02:39 PM   #601
JLOP is offline JLOP  France
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Quote:
Originally Posted by chaparK View Post


I had a quick look at AD1865 datasheet, and it doesn't seem to support I2S. I'm not sure whether we talk about the same chip though, the one I looked at is an obsolete part from AD with 18-bit resolution.

If that's the one, then you'll need additional glue logic if you want to hook these DACs to Najda on the expansion port.

Now I'm wondering: the boards that you have, how do you feed audio in them? If you can feed SPDIF, then you just plug your boards to Najda's SPDIF outs and it's done.
Yes you are right, it's an old DAC but with a reputation of being one of the most natural sounding ever. Did not tried all of course but very happy with it. The design of the board is a clone of a famed NOS Audionote designed DAC, although not multi-channel. I feed it in SPDIF.

What worries me is that in XO application, eg 3 channels, I'll have one stereo DAC for Woofer L/R, another for medium and a third one for tweeters, all with their own clock. Isn't it a problem with phase or Jitter ?

BR
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Old 12th March 2013, 02:56 PM   #602
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Understood about the enclosed - I will make it enclosed
I'm used to trouble shooting 480v DC KT88 valve amps.
Enclosed ones I've been able to find are few and far between at the rating / spec needed over here. Someone will no doubt prove me wrong...

Found this one that looks promising

http://www.xppower.com/pdfs/SF_ECP40.pdf

Bit beefier than needed but the lower models available here don't have such good regulation figures.
+ as Nick pointed out, I will have plenty of power for the expansion board for 5 / 6 way in the future.

Gonna be fun to start this project...
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Old 12th March 2013, 03:12 PM   #603
jcga is offline jcga  France
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Ladies and Gentlemen,

I received my board yesterday... and fortunately I have a couple of days off. I did some interconnections yesterday evening and here is the first power on !

As you can see on the picture, the idle consumption is about 5VA (3VA on the +/- 12V) and less than 2VA on 5V. I measured 1.5VA in Standby mode.

On the right side of the picture is some of the measurement gear that I will use to check the board now.

Stay tuned

Best from France
JC
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File Type: jpg Najda_first shot.jpg (359.6 KB, 535 views)
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Old 12th March 2013, 03:18 PM   #604
chaparK is offline chaparK  Luxembourg
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Congrats JC!
And beautiful LCD display!
(Et un espace de travail qui respire le serieux!)
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Old 12th March 2013, 05:49 PM   #605
JLOP is offline JLOP  France
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avec la collection complète de l'Audiophile
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Old 12th March 2013, 06:19 PM   #606
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Very nice. I like the power supplies
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Old 12th March 2013, 06:59 PM   #607
jcga is offline jcga  France
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I have started to play with it...

On first picture where you can see measurement of a quick three ways Linkwitz Riley 4th at 150 and 2kHz. The additional high pass curve is the one with the the CS3318 set at 6.0 Vrms. Others are outputed with the nominal output set at 1 Vrms.

Second picture is to show the board configuration where you can set the DAC interpolation filter along with the nominal output.

Be aware of a small bug with the current version of software/firmware, the Bass / Trebble optional controls introduce a phase aberration even without any correction selected. Well, it took me a couple of hours, scratching my head with some measured phase deviation before tracking that one !

Jean Claude
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File Type: png Najda quick filter.png (56.6 KB, 490 views)
File Type: png Najda under control_1.png (77.6 KB, 468 views)
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Old 12th March 2013, 10:05 PM   #608
jcga is offline jcga  France
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A quick illustration of possible use:

on first picture, I have loaded the frequency response of a small mid woofer (Scanspeak 18W4531-G0 obtained by a combination of a near field measurement up to 250 Hz and a free field above on axis. No smoothing at all. You can see how well ScanSpeak was able to control the break up modes ! I love and use this driver by the way!

Chanel 8 is just here to illustrate the target (LR24 150Hz-2kHz).

The next picture is the same response corrected by only a Highself. not bad already !

xx_4a & 4b show you the same driver with the LR24 filters enabled and a couple of EQ added. Please note the vertical resolution (1 dB/step).

The result is quite good but we can see a deviation from theoretical below 100 Hz (only one half of an octave below the cut off freq).

xx_5a & 5b are just to show you that, sometimes, it's better to use different type and order for the filter to meet the target. We are now close to the target down to 60 Hz with the use of a Bessel third instead of the LR24 and all that with only 5 EQ beside the filter by themselves.

So what, at 300€ it looks to me a real bargain, thanks Nicolas. Of course there is a lot of room for improvement but with a firmware labeled at rev 0.3 and a software at rev 0.01 ? congratulation, you have already a winner
Attached Images
File Type: png Najda under control_2.png (95.3 KB, 457 views)
File Type: png Najda under control_3.png (95.2 KB, 438 views)
File Type: png Najda under control_4a.png (125.2 KB, 156 views)
File Type: png Najda under control_4b.png (96.5 KB, 145 views)
File Type: png Najda under control_5a.png (125.6 KB, 131 views)
File Type: png Najda under control_5b.png (96.4 KB, 125 views)

Last edited by jcga; 12th March 2013 at 10:09 PM. Reason: correction
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Old 13th March 2013, 06:01 AM   #609
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jcga - great, thanks for that.


Sorry if this has been covered before. Can we input biquad filter coefficients with this software?
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Old 13th March 2013, 06:14 AM   #610
Shaun is offline Shaun  South Africa
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@ jcga: I had planned to post some of my own efforts here. I use the exact same driver as a mid.

I would really like to see an FIR implementation. Any recommendations for suitable software to do this?
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