Filter brewing for the Soekris R2R

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rickmcinnis

Member
Joined 2006
zfe said:
With the Vref modded DAM I like the NOS filter much more than before.
The smallest step away from NOS is most likely linear interpolation. I think I like it even better. I have attached it. Perhaps someone wants to give it a try.

The impulse response is triangular and thus the frequency response sinc squared.
Click to expand...

Dear zfe,

With all of the variations for vref I would like to know what you have settled upon.

Tell me, please,

Thanks,
 
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zfe

Member
Joined 2014
rickmcinnis said:
Dear zfe,

With all of the variations for vref I would like to know what you have settled upon.

Tell me, please,

Thanks,
Click to expand...
Just 2700uF parallel to the output cap (I will probably test also other things in the future),

I think any kind of the proposed Vref mods solves the problem with the High frequency noise and is a huge step forward. The variants improve that further but are "fine tuning".
 
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ylingf

Member
Joined 2004
zfe said:
With the Vref modded DAM I like the NOS filter much more than before.
The smallest step away from NOS is most likely linear interpolation. I think I like it even better. I have attached it. Perhaps someone wants to give it a try.

The impulse response is triangular and thus the frequency response sinc squared.
Click to expand...

Not sure what I am doing wrong, but I have total silence with this filter. Changing to NewNOS the sound came back.
 
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zfe

Member
Joined 2014
ylingf said:
Not sure what I am doing wrong, but I have total silence with this filter. Changing to NewNOS the sound came back.
Click to expand...
If I use the posted files I have the same problem.
The problem seems to be that the name of the file is too long (I wanted some speaking names).
If you change e.g. the name to Linear.skr it works for me.
For convenience I attached the same with shorter names.
 

Attachments

  • Linear_Interpolation.zip
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aive

Member
Joined 2013
zfe said:
The frequency domain filtering assumes a periodic and time invariant signal to produce the "perfect result". I tested some periodic but not time invariant signals, and the difference from what you would like to see from the "perfect" filter is quite significant.

Usually the argument is that speech/music is not time invariant but you apply the fft only to a short snapshot, which is time invariant in first approximation, i.e. the filter does roughly what you expect.

By the way, the same problem appears with long FIR filters in time domain, if the FIR filter is longer than the number of samples the signal can be assumed to be approximately time invariant.
Click to expand...

Hey zfe do you think the front and end issues can be resolved via zero padding at the front and end? Or application of a window function to make the signal appear periodic?
 
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arf

Member
Joined 2006
sacd

spzzzzkt said:
There was a fantastic free SACD produced by DPA Microphones around 2008 called "Miking a Grand Piano". It's intended to demonstrate different mic configurations, and has 8 or 9 tracks of the each performance captured with different setups. Because the recordings are intended to illustrate mic and array performance there is no additional effects or production applied. The music is not the most thrilling stuff you've ever listened to, but it is a very useful reference for judging system performance if you can track it down.

DAD - News Miking a Grand Piano - a Super Audio CD by DPA Microphones

I really need to find someone who can rip the SACD layer...
Click to expand...

Hi Paul, if you are still interested I could rip this for you on my PS3 (PM me).
cheers
Danny
 
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PanagiotisPapadakos

Member
Joined 2013
After a long time I was able to play with my DAM. I upgraded it to 0.99 firmware version and used the EQHQ v1 variations of Paul EQHQ variations v1 | moreDAMfilters.

Unfortunately my truepath is still out of the game, so I used a diy headphone amp using opa 2227 and a pair of cheap headphones (Samson SR850). After some hours of listening and playing with filters my preference is the following: NOS > Low delay > {EQHQ family}. I find the latter ones to be a bit thin and not so natural after some time, altough they seem sharper and I think with a better stage, while the NOS and in a lesser degree the Low delay offer more full bodied instruments. I am not sure about the soundstage though. I am not used checking things using headphones...

What are your observations?

P.S.
1) It seems that this thread has silenced out, after Paul's departure :-(
2) I have not done yet any Vref mod. I only have remove the opamps of the balanced output.
 
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PanagiotisPapadakos

Member
Joined 2013
TNT said:
Do the opamps really interfere with the direct outputs? How and what is the impact on the direct outputs?

//
Click to expand...
Well, unfortunately I can not say for sure, since I am not used in this setup (headphones). I have to fix my main system to tell you for sure. But I think there is better attack and more details (I heard some very quiet harmonics I have never heard before).

P.S.
Somebody has to take measurements for this mod
 
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SebastianL

Member
Joined 2013
I just installed the v.0.99 firmware and can't get the 1021filtNewNOS and a couple of other older filters to work. LED keeps flashing. I've retried several times. However the filter pack included with the new formware works just fine. So does some of the new filters Paul are making on his website, for instance revised EQHQ variations filters
What is wrong? Isn't the new firmware backwards compatible?

(Sorry if this has been addressed before, but I haven't been around for a while.)
 
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SebastianL

Member
Joined 2013
Invalid command

I'm not having any luck typing that, presuming it's at the prompt in the uManager right?

invalid_command_F7_zpsq7ibxcse.jpg
invalid_command_F7_zpsq7ibxcse.jpg

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