Sharp DSP notch filter

Ben Bradley wrote:

>    Here are my thoughts after reading the whole thread (I DID learn C
> 22 years ago - didn't make me rich, but it paid a lot more than
> cleaning toilets in recording studios, and probably even more than
> designing pro audio equipment).
>
> In sci.electronics.design and comp.dsp, On Thu, 21 May 2009 02:54:36
> +0100, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>
> >I am proposing to engage on a project regarding mains voltage 'purity'
> >(and absence of ) with regard to audible clicks and pops in high-end
> >professional and hi-fi audio equipment.
> >
> >Typical EMC filters operate in the RF band and are threfore no use to
> >filter audio 'in band' noise that can travel through transformer
> >interwinding capacitance etc.
> >
> >I have found some of the TI INA series that will with suitable
> >preconditioning, tolerate mains voltages and give excellent common-mode
> >etc rejection. So assembling a 'preamp' front end should be no problem.
>
>    From what others posted, I'm thinking you might want to make
> several of these, to also measure things like the neutral voltage and
> the ground voltage (maybe referenced to your own ground stake you put
> in the ground outside the window or door, on the opposite side of the
> building where the main power comes in). Make these to withstand a
> kilovolt or more on the inputs (use several series resistors in each
> leg). That way you can see common-mode signals as well as
> differential.
>
>
> >What I will need to do however is to filter all the mains frequencies
> >and harmonics to a very large degree.
>
>    You say elsewhere you want to see the results in "real time." I
> interpret that as "not having to wait 30 seconds for processing," that
> a half-second or two seconds might be acceptable.
>
>    Others have said it, but I also see this as a PC application. A USB
> audio interface with four inputs should work (you probably want 24bit
> samples - if USB can't do 48/24 and 4 channels, you then use a desktop
> machine (or firewire, whatever), perhaps powered by a battery backup
> to insure line isolation, with a 4=channel or 8-channel card). Three
> inputs are for hot-to-neutral, neutral-to-your-ground,
> ground-to-your-ground, and the forth is the balanced output (with
> ground not connected!) of the mixer/console/UUT.
>
>    You run this thing, and it samples data continuously. When the
> mixer has an output (or when there's an anomalous output on any of the
> other three inputs), the thing samples a few more cycles, then stops
> and does the filtering (on data that's a few cycles long), and shows
> the areas of interest, both with and without the 50/60Hz imposed on
> the hot/neutral input.
>
>    This puts all the algorithms in a PC which has plenty of DSP
> horsepower thesedays, and also makes a good multichannel data
> recorder. I'm thinking you (or someone who knows C and PC code
> development) can get the Audacity source and modify it to do this (I
> don't know of the legalities and such of using the code in a
> commercial product, if you have to make the code you add open-source
> or what).
>
>    And you just might want to have more inputs to look at, such as the
> main DC filtering caps of the console. This would show if the
> transient occurs at a time when the rectifiers are conducting.

Hi Ben,

just wanted to acknowledge the thought you put into this ( along with all
the other useful contributors ). I'm going to chew it over and get back
later.

Graham


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On 2009-05-25, panteltje@gmail.com <panteltje@gmail.com> wrote:
> On May 25, 10:10&nbsp;pm, "m...@sushi.com" <m...@sushi.com> wrote:
>
>> You can always dual boot a windows PC.
>
> It can be quite a challenge for a non Unix wizzard to start using
> Linux,
> especially command line tools like humfilter.
> As humfitler is a a simple command line program,.
> written in a simple C, and basically only
> does wav file format input to wave file output,
> it should be easily portable to DOS, and run in
> a MSDOS window in for example XP.
> Perhaps compile with the old djgpp compiler?

Or compile with the current mingw compiler and run it on the
windows command-line

On 2009-05-26, Nico Coesel <nico@puntnl.niks> wrote:
> "miso@sushi.com" <miso@sushi.com> wrote:
>
>>On May 25, 2:21=A0pm, pantel...@gmail.com wrote:
>>> On May 25, 10:10=A0pm, "m...@sushi.com" <m...@sushi.com> wrote:
>>>
>>> > You can always dual boot a windows PC.
>>>
>>> It can be quite a challenge for a non Unix wizzard to start using
>>> Linux,
>>> especially command line tools like humfilter.
>>> As humfitler is a a simple command line program,.
>>> written in a simple C, and basically only
>>> does wav file format input to wave file output,
>>> it should be easily portable to DOS, and run in
>>> a MSDOS window in for example XP.
>>> Perhaps compile with the old djgpp compiler?
>>> Several of my programs have been ported to DOS by people.
>>> I am sure you can somehow send the wave output to a soundcard
>>> even in MS software.
>>
>>It's been my experience that it is easier to compile software under
>>Linux. The lack of compilers for windows is the issue.  I assume to
>
> Look for Mingw. Thats a GCC that works fine to compile software under
> Windows. Still, more complex programs cannot be compiled easely
> because of the Linux build tools.

You can rin mingw on linux, or many of the build tools are portable
to windows (modulo the limitations of the windows command-line).

Jasen Betts wrote:
> On 2009-05-26, Nico Coesel <nico@puntnl.niks> wrote:
>> "miso@sushi.com" <miso@sushi.com> wrote:
>>
>>> On May 25, 2:21=A0pm, pantel...@gmail.com wrote:
>>>> On May 25, 10:10=A0pm, "m...@sushi.com" <m...@sushi.com> wrote:
>>>>
>>>>> You can always dual boot a windows PC.
>>>> It can be quite a challenge for a non Unix wizzard to start using
>>>> Linux,
>>>> especially command line tools like humfilter.
>>>> As humfitler is a a simple command line program,.
>>>> written in a simple C, and basically only
>>>> does wav file format input to wave file output,
>>>> it should be easily portable to DOS, and run in
>>>> a MSDOS window in for example XP.
>>>> Perhaps compile with the old djgpp compiler?
>>>> Several of my programs have been ported to DOS by people.
>>>> I am sure you can somehow send the wave output to a soundcard
>>>> even in MS software.
>>> It's been my experience that it is easier to compile software under
>>> Linux. The lack of compilers for windows is the issue.  I assume to
>> Look for Mingw. Thats a GCC that works fine to compile software under
>> Windows. Still, more complex programs cannot be compiled easely
>> because of the Linux build tools.
> 
> You can rin mingw on linux, or many of the build tools are portable
> to windows (modulo the limitations of the windows command-line).

Cygwin gives you a proper Linux command line under Windows.

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