The Best Method to Remove Hiss from Analog Tapes?

[mjurick]

I've been experimenting with many different variations of applying the Dynamic Noise Filter and Continuous Noise Filter to remove hiss from analog recordings.

I've found that the Dynamic Noise filter works best b/c it removes hiss without introducing "weird artifacts" that the Continuous Noise Filter introduces sometimes.

However, when using the DNF, it has a tendency to remove too much high end and "dulls" the original sound. So I apply a light setting of DNF - but then, it sometimes sounds "dirty". I've found the best approach is to apply a light setting (low threshhold 0- 150/ high feq 4000-6000) and then apply a second layer of the Continuous Noise Filter using an attack of 40 and release of 80 and Attenuation of 4 or 5, very low.

This almost works to my satisfaction. But I feel I could be doing something better. Maybe someone could explain to me how the frequency slider on the DNF works? Could anyone *PLEASE* recommend the settings/variations/etc that have worked for them where the end result is good hiss removal, but no sacrifice of the high end?

I would greatly appreciate it!

PS: In the tip pop-up window, there is a tip that says DC-ART is addictive. It is! I've been toying with so many different settings that I can't pull myself away until I get it "just right". Please help!

[Craig Maier]

Re: The Best Method to Remove Hiss from Analog Tapes?

I would recommend spending some time experimenting with continuous noise filter for removing hiss. It is the best filter for this application. It can be made to remove noise with no residual artifact. After you take a noise fingerprint, you need to go in and manually adjust the upper frequency blue inflection points on the graph with the mouse. You will find that there is a position where the noise is removed and no artifact remains. You may want to set the attenuation to about 25 when doing this with the attack at about 5 mSec and the release at about 20 mSec. I hope that this helps.

[mjurick]

Re: The Best Method to Remove Hiss from Analog Tapes?

Thanks for your quick response - it had great info. Can you advise me on what/how to adjust the upper frequency blue points? I'm not sure of the correct positioning.

Also if you suggest an attack speed of 5 and release of 25 - why is the default 40 and 80 respectively? Isn't that a big difference? Also does the attack speed and release have an effect on possible artifacts that can be introduced?

Also, could it also be proper to set the attenuation to 14 or 15 and run 2 passes instead of 1 at 25? What's your advice on this?

Again, thanks so much for your advice. My goal is to keep the most "high-end" possible when removing hiss.

-Michael

[Craig Maier]

Re: The Best Method to Remove Hiss from Analog Tapes?

I just use preview mode and my own sense of hearing to determine the optimal position for the blue inflection points. They can be moved globally up and down by the shift threshold control and they can be individually moved with the mouse. Click on a point and you can drag it up (raises) or down (lowers) the threshold for that point. You can also move any particular point left (lower frequency) or right (higher frequency) to place it more optimally. I have never had to run the filter twice since I am able to get the proper results with one pass. I guess it just takes some practice and experience. I can de-noise a file using that filter after playing with the parameters for only about 30 seconds now. As for the attack and release times, there is a tradeoff between speed, artifacts produced, and transient response. Slow moving music can withstand slower speeds while extremely dynamic music requires fast settings. Release should be set longer than Attack time as a general rule.

[mjurick]

Re: The Best Method to Remove Hiss from Analog Tapes?

>Slow moving music can withstand slower speeds while extremely dynamic music requires fast settings. Release should be set longer than Attack time as a general rule.

How much longer? Let's say the attack was set to 160. Could the Release speed be equal or somewhat greater, like say, 175? What are the sound results if the release is around the same as the attack?

-MJ

[Craig Maier]

Re: The Best Method to Remove Hiss from Analog Tapes?

My general rule of thumb is that the release time should be at least twice as long as the attack time, - - often longer. The reason for a longer release time compared to the relatively short attack time is the fundamental nature of music. Musical transients build up quickly and exponentially decay much more slowly. Imagine someone plucking a guitar string. The point at which the string is released produces a note envelope with a very fast rise time. But the envelope of the decay time is relatively slow unless dampened by the player. Experimentation is the best way to adjust the attack and release time for the Continuous Noise filter. Use the "keep residue" feature to be sure that you are not destroying any transients with your settings if you are not quite certain.