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Old 21st February 2015, 08:58 PM   #161
soekris is offline soekris  Denmark
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Quote:
Originally Posted by TNT View Post
Cool.

Did you litsten to MB2b Sören?

//
No, there is no point for me to listen to it as:

1) The filter is incorrect to start with.
2) I don't know how it's made
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Søren
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Old 21st February 2015, 09:10 PM   #162
TNT is offline TNT  Sweden
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So You have only listened to your own filters?

//
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Old 21st February 2015, 09:39 PM   #163
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Something's wrong with the MB2b, TNT - I set it up and my DAC went into a restarting cycle. It won't start up correctly until I reload another filter.
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Old 21st February 2015, 09:43 PM   #164
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Originally Posted by leehan View Post
rePhase file attached.


IP filter you mentioned has similar tradeoff (higher stopband floor). I hope somebody actually tests this for image attenuation and other criteria. I don't have any means to do so and time to set up one at the moment.
rePhase file doesn't appear to be attached?

If you want to visualise the effect of the filter you can use SoX to do so. It won't be exactly what you'd get from the output of the DAM1021 but still better than nothing.

The way I've been doing it is:

Code:
sox  /path/to/input.wav -r 352.8k /path/to/output.wav vol 8 upsample 8 fir /path/to/firfilter.txt
If you see clipping errors reported, drop the vol setting by 0.1, rinse and repeat, until you get no errors.

The output file will be up sampled to 352.8k have the selected fir filter applied. You can then open up with Audacity, Baudline or your preferred spectrum analyser and see the result. Anything you see above Fs/2 is a mirror image.

On OS X you can drag files into the terminal to insert the file path which makes a bit easier.

If you want to see what filter curves SoX is outputting with various the guru tweak settings grab a short - 3 seconds is heaps - .wav containing white noise. Google should turn up a few sites that have online test file generators, these are fine for the task.

Code:
sox /path/to/input.wav /path/to/output.wav gain -h 0.1 rate -m -I -b 90 -p 28 352.8k
The gain -h 0.1" setting provides 0.1dB headroom for any following effects, and might need to be adjusted to avoid clipped samples.

"rate" is used to upsample, interpolate and dither. Settings in this case are those posted by John Swenson in a thread linked earlier:
-m medium quality
-I Intermediate phase
-b bandwidth as a percentage of nyquist or fs/2 (= 19845 Hz for 22050Hz)
-p phase setting, 0=minimum, 50 = linear-phase. 28 is a intermediate phase, slightly biased toward linear-phase.
352.8k = target sampling rate.

You can then analyse the filtered file and get fairly accurate idea of the filter curve. Don't pay too much attention to the absolute dB values - look at the values relative to the passband. Not sure how you recover the phase information.

Screenshot attached.

It's a bit difficult for me to do any serious listening over the weekend, so will try to test the posted filters Monday.
Attached Images
File Type: png SwensonSoxWN.png (63.9 KB, 347 views)

Last edited by spzzzzkt; 21st February 2015 at 09:45 PM.
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Old 21st February 2015, 09:49 PM   #165
potstip is offline potstip  Turkey
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Originally Posted by TNT View Post
SMPS. Meanwell. I also have batteries. Will try these again. Good that you reminded me. Listening this evening I wasn't to thrilled.

//
Did you realized soound difference between Meanwell SMNP and batteries?
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Old 21st February 2015, 10:04 PM   #166
leehan is offline leehan  United Kingdom
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Paul,

That's very helpful information, many thanks!

Missing rePhase file in post #141 attached.

One of your new links in the first post helped me understand what REW impulse plot is about, it's in dBs!

So I'm attaching that version of the impulse response as well. I aimed a 30% IP. If this calculation is in decibels, I hit the mark at 26% (bottom of the ripples is about -69.5 dB).

I will work with the filter again after analysing it with your SoX method, probably next weekend.

Cheers.
Attached Images
File Type: png Impulse3.png (23.2 KB, 367 views)
Attached Files
File Type: zip IP.rephase.zip (1.1 KB, 17 views)
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Old 21st February 2015, 10:42 PM   #167
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Quote:
Originally Posted by leehan View Post
OK, a post explaining my interest in IP filters.

3. Duration of ringing is affected by the steepness of the roll-off curve. Longer durations affect items 1 and 2, and also transients negatively (3). A slow-roll off is desirable for shorter ringing. But as everybody knows DA artifacts also need to be attenuated.

Hence my preference of IP for 44.1kHz as an optimization between pre and post ringing given the necessary roll-off steepness.
(
Like you, I am philosophically aligned with IP filters. Haven't had a chance to listen to them yet.

I may be misunderstanding this, but I believe that the number of taps also affects both the length of ringing and the level of the stopband. You might be able to trade-off filter length and slope.

Keep up the good work.
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Old 21st February 2015, 10:44 PM   #168
TNT is offline TNT  Sweden
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Originally Posted by RudeWolf View Post
Something's wrong with the MB2b, TNT - I set it up and my DAC went into a restarting cycle. It won't start up correctly until I reload another filter.
Ok... sorry - dont know what to do. Other had also this problem. On the other hand, other succeded.

Strange and I can not offer any ideas I'm afriad

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Old 21st February 2015, 10:55 PM   #169
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Quote:
Originally Posted by leehan View Post
Paul,

That's very helpful information, many thanks!

Missing rePhase file in post #141 attached.

One of your new links in the first post helped me understand what REW impulse plot is about, it's in dBs!

So I'm attaching that version of the impulse response as well. I aimed a 30% IP. If this calculation is in decibels, I hit the mark at 26% (bottom of the ripples is about -69.5 dB).

I will work with the filter again after analysing it with your SoX method, probably next weekend.

Cheers.
Change centring to "Middle".

Red is centering = middle
Blue is centering = 35%

Slightly more pre/post ringing but a massive improvement in stop band rejection at Nyquist. There is about 1.5dB less roll-off at 20kHz using the "middle" setting.

I've added a couple of zoomed plots showing the difference at 20kHz and 22kHz. You can see the reduction of roll off at 20kHz mentioned above and 10+dB improvement in rejection at 22kHz resulting from this single change in configuration.
Attached Images
File Type: png MiddleV35_FR.png (38.1 KB, 346 views)
File Type: png MiddleV35_IR.png (40.3 KB, 356 views)
File Type: png leehan20kRO.png (40.4 KB, 328 views)
File Type: png Leehan22K.png (36.0 KB, 83 views)

Last edited by spzzzzkt; 21st February 2015 at 11:12 PM.
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Old 21st February 2015, 11:09 PM   #170
leehan is offline leehan  United Kingdom
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Reduces ringing length and amplitude as well... hmm. We need Pos to to explain why he recommended intermediate centering values for IPs. Pos, where are you?

That said, I'd be already happy with original roll-off, better than I expected.

I'll try this version as soon as possible. And proceed with porting it to higher sample rates.

Regarding porting to higher sample rates, I find http://www.auralic.com/download/flex...ilter_mode.pdf filter parameters tables a good starting point.

Thank you.
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