Filter brewing for the Soekris R2R

I can't find lower FW versions as 0.99 on the Soekris site, but I think I still have a 0.9 version somewhere.

My ultimate goal is to try out the 1021filt_1015_Kb16_BW, which I only have the .txt file off.
I used MKROM to map it to an .skr file but with no luck... only silence :D

I'm now going through the backlog here.
This topic is already discussed in the past, let me have a deeper look.
 
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This is time domain performance optimized filter. Noise elevated over 30kHz is residual noise of my measurement ring. This is also source of small ripples on 1kHz square wave.
It’s intended for 44.1/48kHz use, all higher frequencies are bypassed so if higher frequency works for sure performance is suboptimal. Recommended all-rounder is F6. Influence of output stage/buffer is key to perceived sound.
 

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Short update from my side; I still play with the newNOS filter which came with the filterpack and I'm hooked to it.
I also have a Denafrips Pontus 2 and I still need to do a fair comparison but my impressions of the Soekris are that it sounds more 'magical' with really loads of resolution. It comes really close to my Pontus 2...
 

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In the current version of the dam1021 rev7, the RS232 interface is no longer in the same place as described in the manual. Tried to establish a connection to the DAC via the new J10 interface, unfortunately without success.
What is the Function of J9, I can't find a Description of it does anyone already have experience with the new boards, what has changed?
 
Hi everyone. My DAM 1021 rev. 1 firmware v0.80 has VREF mod (with transistors and 4x 2000uF caps), opamps were removed, also the rectifier bridge, I've added some decoupling caps here and there. 6 PSU caps were replaced by Oscons 1000uf/16V. I fed my DAM with i2s from a similarly modified Squeezebox, both powered by Salas UltraBiB v1.3 at 9V

20211222_015748.jpg


Today I have upgraded the firmware to v1.21, at the same time uploaded 1021filt_F6_C128dp.skr (that I found a few weeks ago) without selecting any particular filter. Then spent a few hours listening. WOW! The difference is huge. This irritating harshness is gone, especially hearable on the piano, more space, more details and it's more like analog! Also, it seems that Soren fixed the pop during switching the sample rate. :)

Now I have just uploaded TNT441Lin2noDC.skr - set it to "linear", it's the middle of the night so the volume level is low, so I need to do a real listening later during the day.

Please recommend to me which skr files to try. Which are your favourites? I mostly listen to lossless 44.1k I'm not concerned about DC as my F2J has caps on the input and output as well.

Thank you in advance. I promise I will give my feedback :)
 
Yes, J10 is labeled GND,TXD,RXD
Here is example interface https://www.adafruit.com/product/954 but any TTL level interface should work. ExtraPutty works for sure.
These USB -> RS232 (TTL levels - up to 5V) don't not work with rev. 1, at least not with mine, I tried with CH340 and FT232 chips. I had to use my 15 yrs old desktop computer with serial port on the motherboard to upgrade the firmware and upload the filters.

https://www.codrey.com/embedded-systems/rs232-serial-communication/
 
tried so far at 44.1k:
TNT441Lin2noDC.skr - F6 - is very good, clean, precise - perfect!
1021filt_F6_C128dp.skr C128dp (don't remember which bank) has something magical, love it despite that it has a lower volume level
1021filt_allgama.skr - there are some strange distortions I think on all banks, I can hear them clearly on male voices
 
ok, I found DIYA_1021filt_noDCmode.skr from TNT post #1833

For me (and my system) the best is EQHQ(F5 - mixed), then C128dp( F6 - minimum), then NOS(F7 - soft), and then "Linear phase" (F4 - linear)

I haven't expected such a big difference after updating the firmware from v0.8 (2015) to v1.21 (2019) and these "filters".

Many thanks for sharing!
 
What did the F4 lack? Just curious as I made that particular filter in that file but not the others...
To my ears the other filters were more open, especially EQHQ and C128dp, more airy, with more HF details, they filled the room fuller than F4. NOS was also too polite comparing to them.
C128dp had some really slight harshness in female vocals, so EQHQ was my choice.

Maybe F4 would be better perceived if used with the output opamps, don't know. I haven't spend days listening, it was actually quite quick test. Maybe I should give it more time.

It might be also related to my system: the raw output of the DAC is connected directly to the power amp (current source) First Watt F2J clone (single stage amplifier with no global feedback). Using full range drivers in Frugal Horn enclosures (similar size to XL).

So where the other 3 filters are coming from?
 
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