Dynamic Filter

[Marc Hildebrant]

Group,

I have tried the dynamic filter with some Edison Cylinder recordings with good results. In the user's guide, I read where the filter is a "single ended" type...i.e. high end.

While I was reading an article written by H.H. Scott, he described a similar type of filter that used both the high end and the low end to reduce the noise. (circa 1946).

Does it make sense to make the Dynamic filter two sided ?

Marc

[Craig Maier]

Hi,

I guess it could be easily done. But, I think that you can get a very similar effect by using the Punch and Crunch (dynamics processor). I would just use the bottom band and set it for expansion (ratio about 1.3). Move the other bands out of the way and just tune the bottom band and that would emulate what you are asking about.

Craig

[Marc Hildebrant]

Craig,

In the article from Scott, he talked about a "vertical" and "horizontal" method of noise reduction. The method Scott talked about was to move the frequency low end points and high end points of the band pass filter with regard to signal amplitude levels. Scott called this method vertical.

The punch and crunch method would be a horizontal method where the signal level is boosted at times.

Interesting stuff.

Marc

[Marc Hildebrant]

Some experiments today indicate that for the Hill and Dale type of records, a low end noise reduction and the high end would help. The hill and dale type of records have more low end rumble than the laterals.

Note: I do use a high pass filter on the hill and dale records, but I still have some rumble left that could be reduced in a "dynamic noise filter" method.

Marc

[Craig Maier]

I have had decent results on Diamond Discs by using the CNF with a very high fft count. Then, I set all of the frequencies above around 200 Hz out of the way (all the way down) so that the only ones being de-noised are the low frequency components.

[Marc Hildebrant]

Craig,

If the CNF settings were down some, say set above the rumble, would it react better ? Maybe let some of the low end sound through...

Marc

[Craig Maier]

Hi Marc,

I am not sure. It probably depends on the power spectral density of the low frequency signal and how that is weighted. Rumble that I have heard over the years varies greatly in distribution.

Craig

[mikeebb]

Curious - but this filter sounds like the "DNL" filter that Philips used to provide on their tape decks. Essentially a variable low-pass filter that varied by recorded level (quieter = more high cut and lower turnover). It was modestly useful on some tapes, but for me was over-aggressive. Or is this what your Punch n Crunch limiter would do?

FWIW, I finally bit the bullet & got the DC8 upgrade. Will install later this week and try it on some ongoing projects. Just in time for 9 to come out, right?

[Craig Maier]

Hi,

As for the Dynamic Noise Filter in DC8, you can make it as agressive or as gentle as you want based on the various parameter settings. Same applies to the Punch & Crunch. They have a very wide range of adjustability.

DC9 is a long way away since we are still in Alpha testing right now of the Forensics9 program. We have to go through full Beta testing of Forensics9 before we release it, which will likely take until early fall of 2014. Then, we must create DC9, which will also have to go through Alpha and then Beta testing. So, DC9 is about a year away.

Craig

Note: Ultimately, we went directly to DC10, skipping DC9 as a member of the product line numerical sequence. It made sense given that it was written to be compatible with Win10, thus easier to remember.