Fathom Synth Development Thread

[RPH]

Thanks for the reply.
Yeah I figured it would be insignificant.
I should have asked the right question, could you at some point add surgical filters to Fathom? As a feature request.
So I can filter out stuff better, like the 20Hz bump.

[FathomSynth]

The ultimate filter for that would be the Eliptic Filter but I have not yet found a good equation for it.
I've been wanting to add it for a long time.
For now you might try the Parametric with Resonance = 10 and Gail -15 dB.
You can pretty much chop out anything with that very precisely.

[RPH]

Your images have FM enabled and you will always get aliasing with FM especially with fractional ratios.

When I turn off Modulate on the detune tab most of the aliasing is gone.
https://i.imgur.com/NFWtOsi.jpg

The fractional ratios sound awesome in Fathom, I keep getting back to that haha.

[AmbieticA]

The ultimate filter for that would be the Eliptic Filter but I have not yet found a good equation for it.
I've been wanting to add it for a long time.

I uploaded a printout from Wolfram Elliptic Filter Model Documentation you can check out here, as there are a few equations that might help you create one.:

http://ambietica.lyonsdenmultimedia.com ... rModel.pdf

Also here is their entire Signal Processing library of equations. You'll find the Elliptic Filter Model document as well as many more Digital and Analog filter designs on this page here:

https://reference.wolfram.com/language/ ... ssing.html

Hope that helps for future reference.

[FathomSynth]

Thanks, but I need the actual equation which is the closed form expression for the elliptic necessary to generate the transfer function based on any set if input parameters including frequency, pass band, ripple ratio etc.

Wolfram is a tool just like Matlab and you have to buy it for a commercial product and even if I did I would never place a DLL with unknown source code inside Fathom. I would need their their C++ source code, and I doubt that is an option.

The Eliptic is very complex and no one to my knowledge has published the equation. The Wikipedia section on the Eliptic does not have it. They have the equation which describes it's shape but that is useless to generate C++ code. There are various academic papers on it, but they are extremely vague and assume you have the DSP knowledge necessary to take the general concepts and generate the closed form expression on your own.

RPH, Detune will cause a lot of aliasing unless you turn off the chorus on all detune voices. FM will also cause aliasing unless you keep the ratio on integers and the amount very low. I just tried FM under these conditions and my Ableton spectrum shows now aliasing at all.

[AmbieticA]

Thanks, but I need the actual equation which is the closed form expression for the elliptic necessary to generate the transfer function based on any set if input parameters including frequency, pass band, ripple ratio etc.

Wolfram is a tool just like Matlab and you have to buy it for a commercial product and even if I did I would never place a DLL with unknown source code inside Fathom. I would need their their C++ source code, and I doubt that is an option.

Darn! Ok, that makes sense. I didn't realize those equations were proprietary for just Wolfram alone. I'll keep digging. I've been looking for a Formant Filter type for awhile, but still haven't found that either. The search continues...

[FrankH]

You guys got me looking up filter stuff today.

This Analog Devices doc has a good description of Eliptic Filters; (page 26)
https://www.analog.com/media/en/trainin ... apter8.pdf

They site: A. B. Williams, Electronic Filter Design Handbook, McGraw-Hill, 1981, ISBN: 0-07-070430-9

It may be sufficient to go with a Chebychev filter.

[mladi]

Wagtunes, your concerns are warranted.

Obviously if a password changes the correct procedure is to let people know.

To be honest my procedure has evolved and it took a while to get it right.

I did not get the email list up and running in a dependable way until late last year. The email list is now very dependable because it is based on the email of anyone who has purchased the product minus a handful of people who requested not to get emails, which is also a list. The official procedure now is when ever the password changes an email goes out to everyone on the list.

I think what happened is that the latest password changed about mid last year just before I had the email list up and running. At the time I just figured when people discovered that their password no longer worked that they would email me for a new one which they did. Obviously this method was very unprofessional, but has since been fixed with the new list.

It's actually going to change again with the next release, but this time everyone will get an email.

Oh OK, our posts here crossed. It's great to have you back by the way, and a sound bank from you would generate a lot of excitement in our user base, so yes that would be awesome. Not to mention it's also pretty lucrative since all my existing sound designers are making on average around $100 per month on their sound banks.

i bought Fathom way back in 2017 and had a pw for the .zip-file. Now i bought the Upgrade to support you and the pw isn't working anymore. No problem but why i have to contact you after a second purchase for the password is beyond me. It's sunday i have a few hours to play around with it but have to wait that you answer me that i can unzip something i paid for two times. No hard feelings of course just sayin'..

[mladi]

dp

[Unaspected]

The Eliptic is very complex and no one to my knowledge has published the equation. The Wikipedia section on the Eliptic does not have it. They have the equation which describes it's shape but that is useless to generate C++ code. There are various academic papers on it, but they are extremely vague and assume you have the DSP knowledge necessary to take the general concepts and generate the closed form expression on your own.

I recall an implementation of an elliptic filter in the Reaktor library - I was going to experiment with it for anti aliasing but my attention drifted elsewhere. I have the ensemble on an HD somewhere so I'll have to look up the name as I can't seem to find it online right now.

[RPH]

http://www.matheonics.com/Tutorials/Elliptic.html
https://dedicatedhosting.pro/cauer-filters-99/
https://www.researchgate.net/publicatio ... IR_filters

[FathomSynth]

RPH,

Those are the best references for the Elliptic Filter I’ve ever seen. Thanks!

The first one even looks like it might be enough to implement it, although as you can see not be easy.

Since you seem to so good at finding that sort of stuff, if you can find me a good implementation of the comb filter I will put it in Fathom. The Comb filter has by far the most user requests.

Mladi,

Hi. Sorry you had to wait for the password, I can easily imagine that would be frustrating especially as the valuable music hours pass by.

We still use the very low tech unzip password. It has to be changed every once in a while and there is no way to avoid this. The last one was active for well over a year. Unfortunately it is going to change again for the next release.

Normally if I am at my development station users get a response for a password request within minutes. However you happen to have caught me while I was asleep.

That being said, your post gave me an idea. I already have a dedicated server which is capable of automated email response (and the server never goes down) so as soon as I get a chance I will update my server to automatically grant password requests as long as the requesting email matches a purchase email. Problem solved.

I will be using a new licensing system for Fathom Extreme starting in the release after the next one which will be version 2.33. However, it will NOT be dongle based and it will NOT be a machine lock. It will only be a user license like the u-he system and users will be able to use their license on as many machines as they want.

The new license system was actually coded by myself and installation is a one button press and will not require any complicated transactions.

The new license system will be mandatory only for Fathom Extreme, but as promised for Fathom Pro it will be optional and users who want to keep the unzip password for Fathom Pro will be free to do so.

Once this is done updating the unzip password will no longer be necessary for users choosing the new system since they will have their own password which never changes.

[RPH]

Those are the best references for the Elliptic Filter I’ve ever seen. Thanks!

The first one even looks like it might be enough to implement it, although as you can see not be easy.

No problem at all, Everett!
The third link made my head spin even more haha, no most definitely not easy.. many props if you get it implemented!

Since you seem to so good at finding that sort of stuff, if you can find me a good implementation of the comb filter I will put it in Fathom. The Comb filter has by far the most user requests.

Think these links should help out a lot, the equation you need is there:

https://recordingology.com/in-the-studi ... culations/
https://ccrma.stanford.edu/~jos/pasp/Fe ... lters.html
https://www.dsprelated.com/freebooks/pa ... lters.html

[mladi]

Thanks for the fast answer and insight Everett now i understand the situation. Keep up the good work!

[FathomSynth]

RPH, Thanks, you are now Seaweed Audio's honorary VP of Research And Development.

Also, one quick question on the comb filter, what is the primary parameter name for the comb filter which most people are use to seeing? I know it is not frequency like most filters since a comb filter is achieved with essentially a simple delay line. Are the units normally milliseconds, seconds, or samples?

Mladi, Cool, I'm going to try to be especially aware of all user's opinions and needs for licensing having been through plenty of liclense hell situations myself. We will need something soon going forward but I will make sure it is Easy with a capital "E". (Like a "Walrus in Goal Easy").

Also, as promised it will not impact Fathom Pro (unless some users want it optionally).