Filter brewing for the Soekris R2R

So, about that TNT3 filter...

I finally decided to build a new output stage, based on a simple but trusted standard topology: Balancing via a 5532 op amp with decompensated feedback paths, AC coupled output, fed by +/-15V. I used NJM5532DD, currently the best sounding one availible IMO and ubiquitous in pro audio and quality unipolar electrolytics bypassed by film caps.

Nothing fancy, the same stuff that is in my mixing console and something almost every bit of music you can buy went through.

It turns out the DAM's onboard output stage was the problem. TNT's latest linear filter sounds perfect with the new stage. :) The bass, the power, the movement, the detail and especially the spatial dimension.

Now NOS sounds overly aggressive and grainy in the high end.

Music as it is supposed to sound! Thanks TNT!

Now I wonder if a 4K filter could even improve on this... ;-)

I had a client who owned Amek 32 ch console with 5534 master bus summing. Ampex MM1100 2" 16/24 track tape MC feeding the Amek.
Seriously great sound. He complained of his mixes 'collapsing' WRT image and bottom end turning mushy when a large numbers of channels were
getting pushed past a certain point in level. He would then basically have to start the mix again being more vigilant of channel levels.

I designed a complete discrete, zero feedback master section running 32V rails and it killed the 5534's in every way. It also solved the collapsing mix issue.

IME, usually better off not to bypass your signal caps with film caps. Use 1 good cap. People usually comment on 'more detail' when electros are
bypassed... detail that wasn't there? Your NP electros go to many 100's of kHz, that should be enough for audio. :)



Joined 2003
Paid Member
There are only 4 user selectable filters: 04, 05, 06, 07. All the other versions you see are either there for different Fs, fixed FIR2, fixed IIR (DC, pree.) or for different data format (DSD).

So the only thing you need to "worry" about are the 4 ones that you already know the relation to the LEDs for.

I think your very "long" question tired folks out :-D so much text... what was the question now again... Uhu.. better not get involved.... ;) ??

Thanks a lot for trying to help me! Finaly I found the helpful person here) Please, help me with understanding the filter insulation and filter chosing process, as I'm kinda still feels like I'm missing something...
So from the tutorial I that first of all I need to install the filter pack with help of "extraputty" software. And then I need to select the filters, in play mode (according to the guide), assigning each filter type for F4, F5, F6 and F7 banks, which belong to the specific type of led indication on my 1421.
But how can I chose the specific filter from the pack I installed, if there is more the one type on each F4, F5, F6 and F7 banks? Please, check the attached picture - to see what I mean


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Exactly! Sorry, that was my bad! I didn't notice that every 04, 05, 06 and 07 filters are specified for every each pcm and dsd sample rate! Thank you a lot for pointing on it.
I have one more question. In the end of the tutorial it says that:
"If you set the filter in umanager, it will remember over a power cycle, if you use F4-F7 in play mode, it will not." What is the difference of setting the filters in a umanager and play mode? In the tutorial it also shows how to set it in a play mode (in a command prompt), but all of the changes that was made like that are going do disappear after power off and all of the default filters will come back again? How can I set the new filters permanently with help of umanager?


Joined 2003
Paid Member
You cant do anything except choosing which set of filters you want to be actively used. There is noting to assign. See it like you have a switch with 4 positions i.e filter set (bank) 4,5,6 or 7. If you give F5 as a command, and depending on Fs (sampling frequency of incoming stream), the corresponding filter will be activated. You choose a whole set (for different Fs)

Thats it.



Joined 2003
Paid Member
When You do +++ you end up in the U-manager i.e. you have a promt. Here You do "set filter = linear", linear = 04 - this will stick even after power off. If you from here do "Exit" (this as also a manager bu the designer didn't understand that this would make for a lot of confusion - especially as this manager don't have a name) and you end up where you can do F5... F4 - it will change your Bank so that you can do quick comparisons but it will not survive a power off.

No filters are "unloaded" or disappears - its just the choice of the active bank that this effects.

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Thank you a lot for help! I think now I understand pretty much everything I need)
However, now I'm facing another problem. I installed driver, set up the port settings, edtraputty and teraterm can see my dac niw, but...when I'm typing comands - nothing happens in command prompt in both software (putty and teraterm)! I tried to connect another keyboard, but still no result! Can anyone help me to solve this problem?
It looks like I have a troubles with key combination...
After several tries I finally get a blinking propmt, when I pressed +++ and was able to type.
So I updated firmware to the latest one 1.21 and installed filter pack.
After I checked the filters list with command "filers [all]", I found next (please check the attached picture). Does it mean now that all of the filters were successfully installed and automatically assigned to F4, F5, F6 and F7, according to their position on the list?
Also, am I understand right: if I'm gonna chose your filter (TNT) with Soekris 1421 red light - it will work only on 44.1 and 48khz and all the rest frequencies will work with default Soekris filters?


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Thank you all a lot for great explanations and help!
Testing new filter pack now (last TNT pack with DC mode) and found strange thing with NOS filter: on 96 and 192khz (didn't test higher yet) the sound is waaaay quiter then on 44.1 and 48khz. The difference is really significant. Is that how it should be or this is some problem I'm facing personally?
I did check all of the frequencies and found out that only on 88.2 and 96khz files, volume level drops down significantly with NOS 07 filer. All the rest type works fine and with no issue.
TNT, would you be so kind to check the filter pack, attached to this post - maybe there is some mistake that cause 88.2 and 96khz sound so quite?
Thank you a lot in advance!


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