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Old 14th April 2013, 11:09 AM   #921
Rixsta is offline Rixsta  United Kingdom
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Hi, is there a DAC with a 4 channel (or more) ADC with it too ? around to buy or to diy
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Old 14th April 2013, 02:23 PM   #922
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Thanks Dave. I'll make that change. To me, the idea of actually cascading biquads is also a bit pitiful because that's wasting DSP resources.
How will you implement the mixed IIR/FIR mode? The most obvious way would be to simply give coefficients b0,b1,...,bM,a0,a1,...aN in a text file.

That would allow for the greatest flexibility.

Regarding OP amps I'm laying low with that for now. Much more important to get everything up and running.

/K
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Old 14th April 2013, 04:44 PM   #923
Ryssen is offline Ryssen  Sweden
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Am I right when I say that the opamp next to the edge of the PCB is for channel 1 and 2?
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Old 14th April 2013, 05:42 PM   #924
Shaun is offline Shaun  South Africa
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Nick, would it be possible to detect and reject a SPDIF signal that is not a proper stereo signal? I am taking a digital out signal from my AV processor. Under some conditions, this port can output a 5.1-format data stream. Via Najda, this comes through as either a motor-boating hiss (5.1 active) or a high-pitched sound (PVR paused).
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Old 14th April 2013, 07:36 PM   #925
jcga is offline jcga  France
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Originally Posted by Ryssen View Post
Am I right when I say that the opamp next to the edge of the PCB is for channel 1 and 2?
According to the CS datasheet, two opamp are needed to feed the offset-ed differential input of the AD so the 2 eight pins opamp near to the edge are for inputs.

The other four are for outputs

Jean Claude
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Old 14th April 2013, 07:42 PM   #926
Ryssen is offline Ryssen  Sweden
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The other four are for outputs
Yes,and wich one of them is channel 1-2?
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Old 15th April 2013, 06:08 AM   #927
jcga is offline jcga  France
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Originally Posted by Ryssen View Post
Yes,and wich one of them is channel 1-2?
Well, have a look on the component side of the PCB, you can clearly see the traces leaving the input plugs...

Jean Claude
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Old 15th April 2013, 10:22 AM   #928
chaparK is offline chaparK  Luxembourg
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Originally Posted by alugner View Post
About the +/-12db filter gain. Is such high differences in gain not better addressed by other drivers or power amplifiers? There must be a considerable risk of clipping on the power amplifiers if You need a >24db correction. I might have misunderstood the discussion.
It's for filtering purpose that such a gain is required, not for level adjustment. For example a shelving filter with more than 12 dB of gain.

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Originally Posted by Speedysteve7 View Post
After a bit of work today all is properly encased and working perfectly.

Here she is all mounted up. The display slot took a while. Two 10mm holes and then careful jigsaw out. Rest was with various files, until I was satisfied. Fine emery cloth on file to finish.

Click the image to open in full size.

To get the display flush I had to countersink it in the 8mm thick front panel.

Click the image to open in full size.

This was done with lots of suitable depth 10mm drill holes and then angle grinder with flapper wheel to remove the rest.

Case feet

Click the image to open in full size.

I decided I wanted the expansion board on the left as viewed from the rear. Plenty of space there.

Click the image to open in full size.

Did you spot the mistake I've made in this shot?

Getting the holes in the right place took care.

Matches the MF unit - Could use some gold though and a nice Najda logo and text to indicate what the buttons and LEDs do...

Click the image to open in full size.

Could do with a clean up not finished.

So very sucessful and the push to make buttons have a very nice action to them.
The 5mm hole for the IR works perfectly from the place I use the remote. Actually I just tested it and you can point the remote pretty much anywhere in the room away from the case and it still works!

Now - sit back and listen, with a nice cup of tea
Well, what can I say? That unit looks really good, Steve!!! Congrats and many thanks. I'd like to add a gallery on the website, and I'd like to include your machine.

I haven't spot the mistake you mentioned, but I can see there's no cut for the USB and Relay plugs.

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Originally Posted by Ryssen View Post
I did a wooddenboard mount..
I use Salas shunregulators.
Click the image to open in full size.

Today I have checked the digital input,and the Leds.

But I miss the abbility to invert the phase on each output..
Or is it there?
Yes it is there Forgott about it..
Very nice Ake, that's very serious work. Can I ask your permission to add this pic in the gallery as well? It shows the level of organisation which is required to achieve successfully the project.
(Anyone who wants to send me pics, please do so )

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Originally Posted by kazam View Post
How will you implement the mixed IIR/FIR mode? The most obvious way would be to simply give coefficients b0,b1,...,bM,a0,a1,...aN in a text file.

That would allow for the greatest flexibility.
So I think we have agreed that the FIR/IIR mix would most likely consist in the FIR input processing tab combined to the IIR channel processing tab.

Regarding coefficients, this will be included in all IIR blocks, with the ability to load the content of a file. There will be these coefficient you mention, for biquad sections only - i.e. it's the user responsibility to decompose a higher order filter in second order sections.

Quote:
Originally Posted by Ryssen View Post
Am I right when I say that the opamp next to the edge of the PCB is for channel 1 and 2?
No, the opamp for channels 1 and 2 is actually the 2nd from the left edge.

Quote:
Originally Posted by Shaun View Post
Nick, would it be possible to detect and reject a SPDIF signal that is not a proper stereo signal? I am taking a digital out signal from my AV processor. Under some conditions, this port can output a 5.1-format data stream. Via Najda, this comes through as either a motor-boating hiss (5.1 active) or a high-pitched sound (PVR paused).
We can look at this. There's a flag in the SPDIF streams that says whether it's PCM or something else. We could use this flag and zero outputs when it's not PCM. How about that?

Regarding LCD wiring with the supplied flat cables, here's how I do it:

cable.jpg

Basically the contacts come out of the housing so you can rearrange the order for your particular LCD pin out.

This works only if you don't require more cable length. Also, some of you have more elegant ways to wire the display - this is just a suggestion. (and no, this pic will def no go into the gallery )
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Old 15th April 2013, 11:30 AM   #929
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Originally Posted by chaparK View Post
So I think we have agreed that the FIR/IIR mix would most likely consist in the FIR input processing tab combined to the IIR channel processing tab.

Regarding coefficients, this will be included in all IIR blocks, with the ability to load the content of a file. There will be these coefficient you mention, for biquad sections only - i.e. it's the user responsibility to decompose a higher order filter in second order sections.
I'm not sure I follow here. I think of "Mixed FIR/IIR" as a generic filter transfer function:

H(z) = B(z^-1)/A(z^-1)

where A,B are polynomials in z^-1 and thus uniquely defined by the parameters b0,b1,...,bM and a1,a2,...,aN.

What would be the purpose of dividing this into biquads? Isn't is more efficient just to implement this is as a general filter structure from a DSP op count perspective?

I can understand the need for biquads as that is something people are used to and they certainly have their use. For maximum efficiency it would be nice to see the direct form implementation as well. I guess a check to see if all poles are inside the unit circle would also be great.
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Old 15th April 2013, 02:28 PM   #930
Shaun is offline Shaun  South Africa
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Originally Posted by chaparK View Post
We can look at this. There's a flag in the SPDIF streams that says whether it's PCM or something else. We could use this flag and zero outputs when it's not PCM. How about that?
Sounds like a plan! I'm glad to hear there's a likely easy fix.
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