Filter brewing for the Soekris R2R

[Blitz]

Finally readjusted allpass filter for hopefully satisfy wider group of people. It’s based on one of my early filter, so should be ok but verification is needed.

Some more explanation about allga filters family.
F4 to F6 filters stacks are made identically just with small change in FIR2 stage filter which is new 64 coefficient filter.This small difference allow to make adjustment of sound presentation according to preference.
Second thing that is special in allga family is magnified distortion adjustment with volume. If we set 0db on dac we could get over 5% THD. Lowering volume to c.a -6db on dac almost cancel that effect, so we have 0 to -6 db to adjust harmonics to preferred level.
There is FR with elevated high frequency ca 1.5db
F7 filter is NOS/NewNOS stack for “classical” presentation(volume level works as usually
Anti aliasing for all with IIR filters.

I wanted to try this package on my DAM1941 assuming that the 1021 filters work here as well...welll...error message: "Incorrect Image" when trying to update...is there a pure NOS-Filterpack for 1941 ? IDeally with the first filter being NOS as my friend did not wanted to invest into the font-panel...so he has only one filter, the first one all the time.

 

[hannesie]

Is the difference not the FPGA? In stead of the Spartan there is a Lattice in the DAM 2541

 

[gumisb]

I wanted to try this package on my DAM1941 assuming that the 1021 filters work here as well...welll...error message: "Incorrect Image" when trying to update...is there a pure NOS-Filterpack for 1941 ? IDeally with the first filter being NOS as my friend did not wanted to invest into the font-panel...so he has only one filter, the first one all the time.

You don't need to send "update" command after downloading the filter, just exit and / or toggle filter. You can also change and save the default filter.

 

[Blitz]

Thanks for clarification...just found as well TNTs comment that the Dam1121 manual is more selfexplaing...when I want to select a new default filter...is this done with the run time command:

Fx Filter Type, 4 = linear, 5 = mixed, 6 = minimum, 7 = soft

?

So, when I power off and power on...will the dma1941 remember this new selection as the new default ?

 

[TNT]

There are two ways of changing filters - just to complicate things for the user... Another problem is that the designer has not defined enough terms and concepts to describe the handling in a stringent and pedagocical manner. This is also probably the reson why so many have questions about it.. but Sörens un-paid support staff is here 24 hours a day - yes sir isn't it conviiiinient... Only one out of the two modes of the serial interface is named. I will below use Connected and Unconnected to describe the handling.

- When you don't have a promt, i.e. the serial connections mode directly after power on - lets call that "Unconnected" mode - you can enter e.g. "F5" and the DAC will change filters to F5 immediately. But it will not be permanently stored. If you want to make it survive a power cycle you need to use an other command in "Connected" mode i.e. when you see a promt - you get that after entering +++ in Unconnected mode. In Connected mode you use the "Set" command to do permanent changes - it will be instantly effectuated - see the "Manual".

To get back to Unconnected mode from Connected mode, use command "Exit".

//

 

[Blitz]

Ahhhh, great, now I got it...i think..

So, procedure will be:

• Power on and have serial connection, wait for status message
• type "+++" to get into uManager
• type "set filter=minimum"( for F7 as an example)
• type "exit"

So, i will start to learn what you guys did in the meantime, I think i used TNTs filterpack amd liked the NOS filter within best sofar...more direct than the rest...I worked on many other topics, but niw the resolultion of my system comes to a point where the filters will be even more audible...

 

[euro21]

Another solution: use any computer based device "programming" 1941 on power on.
I used Arduino.
https://www.diyaudio.com/community/threads/gb-for-ardam-lite-bare-pcbs.306521/page-9#post-5706523

It's has complete display control, remote management (filter changing, volume settings), .... but in recent years I didn't use any of them.

 

[TNT]

....my system comes to a point where the filters will be even more audible...

... and you will start to appreciate the F4 :-D

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[Blitz]

I have a question again, sorry to bother you...I bought a dam1941 when it came out, updated it to 1.23 and put the TNT/spikestabbern version on it with f4 the original Soekris Filter and F7 the NOS i likes best sofar.

Now, I bought for a friend another dam1941 like a year ago, not sure if anything has changed.

• i uploaded the NOSversion of gumisb first on it...and found that some of my music is highly attenuated like -12db or more...only when playing 96khz/24 files..... far too low to enjoy music, i need the voltage gain.
• so, i simply put the old TNT/spikestabbern version (1693) on it...same issue !!! I never had that issue before with my old own Dam1941 where this exact filter pack is playing for years
• So, i downloaded Soekris original filter, back to delivery status...now we have same volume, no matter if 96khz or not.
• So, i downloaded TNT/spikestabbern again setting again: Same issue as before...highly attenuated, but only at 96khz/24...

My old dam1941 where I had not the gumisb version on does not have this issue...I suspect there is a setting which has not been cleaned when uploading firmware /soekris filter pack 1.23 ?...my suspiscion is because my Setting F7 as default as well survived the firmware update...So, düthe DAC is not completely resetted to delivery status...

 

[Blitz]

in addition...what does df do ? Dump flash content...leads to....? Sounds Dangerous...

 

[TNT]

I think it lists/prints the memory content... I never tried it...

My part of that filter file, i.e. F4 and F4 only do actually have some additional attenuation in the filter - 3,1 dB to avoid interovers.

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[Lawrenceho]

I am so sorry if this question sounds stupid, but why isn't there any NOS filter for DSD (2.8MHz + sampling rate)?