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Filter brewing for the Soekris R2R
Filter brewing for the Soekris R2R
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Old 15th February 2015, 07:34 PM   #31
MisterRogers is offline MisterRogers  United States
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Filter brewing for the Soekris R2R
I for one are happy to get the filters a bit before the specs - as long as the specs come.
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Old 15th February 2015, 07:37 PM   #32
kuribo is offline kuribo
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If one was using multiple boards in an active system, three or four way, would there be some advantage to using narrow frequency ranges in the filters to only cover the frequencies each board would be seeing?
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Old 15th February 2015, 07:43 PM   #33
TNT is offline TNT  Sweden
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I would say yes if the desired f0 and steepness covers your requirement for out of band alias suppression as these would be less steep filters which is probably good.

//
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Old 15th February 2015, 08:01 PM   #34
TNT is offline TNT  Sweden
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OK - I hope then that you are OK with 2 more filters. I will post info on all of tomorrow morning.

//
Attached Files
File Type: zip MB2.skr.zip (5.6 KB, 60 views)
File Type: zip MB3.skr.zip (5.6 KB, 51 views)
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Old 15th February 2015, 09:17 PM   #35
spzzzzkt is offline spzzzzkt  Australia
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TNT,

I've had a listen to the MB1 filter, and my feeling is that it's fairly close to Søren's original.
Using Miles Davis' "So What" as a reference, it has the same lack of body to the opening piano chords and thinness to the lower registers of the double bass that I was trying to address. My previous 4 x PCM63P and jfet I/V DAC had that richness in spades and the DAM sounds slightly anaemic but highly detailed in comparison.

The shoutiness on Album//Rise is pretty well tamed.

Clearly it's a matter of taste and system - I'm using Hypex UCD180HG+HxR modules and Audiovector Mi1 Signatures fwiw.

cheers
Paul

Last edited by spzzzzkt; 15th February 2015 at 09:28 PM.
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Old 15th February 2015, 09:18 PM   #36
gazzagazza is offline gazzagazza  New Zealand
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Quote:
Originally Posted by zfe View Post
The 29 kHz will turn up as 44-29=15kHz (first we are in the lower side band which is mirrored frequency wise).
But still I also feel that the rolloff is too slow.


It would be a strange design concept to combine slow digital filter with a fast analogue one. Ususally the arument is you can do the fast ones more precise digital.
Show me a recording with significant levels at 29khz, or in fact tones equivalent to the imd test and then I will worry about aliasing. Musical harmonics fall away to very low levels by the time we get to 20khz.
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Old 15th February 2015, 09:19 PM   #37
spzzzzkt is offline spzzzzkt  Australia
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Quote:
Originally Posted by TNT View Post
OK - I hope then that you are OK with 2 more filters. I will post info on all of tomorrow morning.

//
Yes of course.
The information will help make sense of what works and what doesn't...
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Old 15th February 2015, 09:43 PM   #38
zfe is offline zfe
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Quote:
Originally Posted by gazzagazza View Post
Show me a recording with significant levels at 29khz, or in fact tones equivalent to the imd test and then I will worry about aliasing. Musical harmonics fall away to very low levels by the time we get to 20khz.
OK, I maybe formulated it no well.
We are talking about 44.1kHz recordings. If the recording was made well (using the apropriate low pass filters, reducing to DC-22.05kHz, during recording resp. generation of the 44.1 file) there are no noticable aliases, and if there are aliases in the recording we can not get rid of them in the DAC.

But due to the oversampling of the DAC we get duplicates of the DC-22.05kHz frequency spectrum of the recording at frequencies above 22.05kHz. The first one are the 44.1kHz-f, for f in DC-22.05kHz.

So the 15 kHz part of the reording will also show up as a copy at 29kHz at the DAC output.
We need a resonable fast filter to suppress the "29kHz".
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Old 15th February 2015, 11:25 PM   #39
spzzzzkt is offline spzzzzkt  Australia
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Quote:
Originally Posted by TNT View Post
I wil do so. I didnt see any instruction for in which order. If I'm not allow to post filters 24 hours before specifications I will not post them here. Knowing the technical aspects dont make up for an objectibe test I think..

Your call.

//
Yeah fine.

What I don't want to see is posts of filters that are then treated as "secret sauce" with no disclosure or discussion of the way they were built possible.
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Old 16th February 2015, 04:40 AM   #40
spzzzzkt is offline spzzzzkt  Australia
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MB1 looks very similar to Søren's factory filter however the roll off is steeper.

The slow roll-off is very slow in comparison.

In order the charts are MB1, Søren Default, MPSRO441v2

The plots are done with white noise, with DAC set to V+00, and audio interface input gain levels at minimum. I've had to attenuate the white noise source to prevent the inputs clipping. The levels were not touched when testing so any variation in level is the result of the filter configuration.

The method is a slackass version of NwAvGuy's testing procedure.

Note: Ignore dB scaling, this is illustrative only.
Attached Images
File Type: png MB1_WN.png (162.9 KB, 750 views)
File Type: png 1021Default_WN.png (125.0 KB, 728 views)
File Type: png MPSRO441v2_WN.png (173.3 KB, 725 views)

Last edited by spzzzzkt; 16th February 2015 at 04:45 AM.
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