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AN1x filters are not correctly modeled

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  • AN1x filters are not correctly modeled

    I don't like finding failures, but after JP-8000 / 8080 filter distortion issue i think it is better to publish information, seek for possible solution or beg big companies to do something about it, than just to sit and do nothing.



    This have been bugging me for quite a long time. When playing Yamaha AN1x i've noticed that when switching from 12 dB to 18dB and specially to 24 dB, the change is minimal. Yesterday i decided to clear this out once and for all. Testing was done using AN1x white noise oscillator. Filter was set to near half position (60/128), resonance 0, filter keytracking 0 and filter env depth 0. Other oscillators, ring mod and feedback were set to 0. Effects were off.

    12 dB filter:



    Difference between one octave (450-900 Hz) turned out to be 12.75 dB. This is more closer to 13 dB than 12 dB.


    18 dB filter:



    Difference between one octave (450-900 Hz) turned out to be 15.75 dB. This is not good! You want to emulate the TB-303? Forget it. Looks like you will need to use the 24 dB one (see next filter type).


    24 dB filter:



    Difference between one octave (450-900 Hz) turned out to be 19.15 dB. This is far too much difference to be tolerated. If you want short Jupiter 6 type 24 dB basslines or arpeggios - forget them. The filter is too shallow. It is more like a 18 dB filter, so ironically if you want a 18dB filter, you need to select a 24 dB one.

    For comparison on JP-8080 (and other synths) when you switch from 12dB to 24dB you can immediately hear the difference. On AN1-x it sound like a small change, and when switching from 12 to 18 almost no change at all.

    In short
    The Yamaha AN1-x does not contain true 12, 18 and 24 dB filters. Instead it offers some "half-filters" with values of 13, 15 and 19 dB. This can be interesting for building classic 12dB (Jupiter 8) type of pads and strings, but when you need a strict 24 dB filter for percussive instruments, dance basslines or JP-6 arpeggio lines, the provided 24 dB one simply doesn't cut enough.

    If anyone is interested in doing more tests, please use the above settings and same frequency range when making spectral analysis. (This however doesn't change the fact that AN1-x offers a huge sound palette thanks to its deep and complex routing - it's a really nice synth, perfect for sound design and special effects.)

  • #2
    Sounds like Yamaha's got some 'splaining to do.
    Gear: buncha stuff and a couple bazilion cables

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    • #3
      Damn...Yamaha better fire up the ole' Time Machine and travel back to 10 years ago and fix this travesty.
      All jokes aside, it would be interesting to see an analysis on many synths to measure their filters, compared to their factory specs.
      It figures you wouldn't get it. "A Season in Hell" was a head of it's time. -Jimmy James

      Good deals with: Adam Poland

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      • #4
        Don

        It might be worth running the same tests against a couple of other synths for comparison
        Last edited by Gus Lozada : Today at 09:57 AM.

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        • #5
          It might be worth running the same tests against a couple of other synths for comparison
          Yup, already done it.

          Roland XP-30 12 dB filter:

          Result is exactly 12 dB.


          Roland XP-30 24 dB filter (using structure):

          Result is exactly 24 dB.


          Of course i can make few more tests, but it won't cure the problem. I can't figure out why they put "24 dB" mode when it sounds like 18 dB - in fact, results show it is a 18 dB filter (well, 19.15 dB to be exact).

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          • #6
            Maybe they reversely truncated 3.2 pole to 4 pole filter
            Alesis A6 Andromeda SCI Prophet-5 Korg Trident Roland Juno 106/60 DSI PolyEvolver Rack Moog Little Phatty Vermona Synthesizer Yamaha DX-7 Casio CZ-3000 Roland D-50 Nord Lead-3 Roland XV-5080 Korg WaveStation AD Yamaha A5000 Sampler Crumar Orchestrator Roland M480 Presonus Comp16&EQ3B

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            • #7
              Yup, already done it.
              Roland XP-30 12 dB filter:

              This graph misses the spike you get when you clonk the resonance up to the horribly squealing noise they still haven't fixed.

              Of course i can make few more tests, but it won't cure the problem. I can't figure out why they put "24 dB" mode when it sounds like 18 dB - in fact, results show it is a 18 dB filter (well, 19.15 dB to be exact).

              I guess whoever made the TB-303 kind of got a "whoops" feeling about that, too.

              "Whoops".
              "Part of an instrument is what it can do, and part of it is what you do to it" - Suzanne Ciani, 197x.
              Synthesizer Programming Megathread - add your tips & tricks or ask how to recreate sounds!

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              • #8
                Hey Don,

                Very cool analysis. Do you find that the slopes on the AN1X filters are dependant on the amp feedback parameters? (I think you would agree that the perceived resonance and cutoff drop ... and more so on the "24dB/oct" filter) when using amp feedback. I am just wondering if the slope is affected also?

                I can hear the low frequencies rise in volume as I adjust the amp feedback, and I wonder if there is a magic number where the 24 db/oct filter is really what it says it is. Of course if that is the case, there is not much resonance available on the filter.

                Best,

                Jerry
                Every society honors its live conformists and its dead troublemakers. - Mignon McLaughlin

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                • #9
                  Interesting, I always thought the 24db sounded weak and I always had a lot of difficulty emulating the AN1x on another synth.

                  I'd be real curious to see where the EX5, CS6x and motif series are at... Have to say though that after dumping it I've never wanted it back.
                  Every man makes a mountain of his life and master plan...

                  Why do you persist Mr. Anderson?

                  We used to joke that Chaz's pec's were rock hard and could deflect bullets, I guess not...

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                  • #10
                    "AN1-x filters are not correctly modeled"




                    That'll probably give it a 'unique character' and make it more sought after in the future.

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                    • #11
                      Don Solaris: If you don't mind, can you tell us what application you are using to generate these graphs?

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                      • #12
                        Interesting, I always thought the 24db sounded weak and I always had a lot of difficulty emulating the AN1x on another synth.

                        Well, i was embarrassed even talking about it, thinking maybe i'm crazy, or maybe it is just in my mind sounding different, i mean, hey! this is Yamaha!, they are Big! If they write 24 dB, then i must be 24 dB!!

                        So it wasn't until i bought JP-8080 and switched from 12 dB into 24 dB position - BINGO! This is it! This is a "switch" from one sound to another, and you can clearly hear how 24 dB cuts away high partials. On AN1-x you need to concentrate deeply to spot a tiny difference.

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                        • #13

                          Well, i was embarrassed even talking about it, thinking maybe i'm crazy, or maybe it is just in my mind sounding different, i mean, hey! this is Yamaha!, they are Big! If they write 24 dB, then i must be 24 dB!!


                          You are not crazy. You have great ears. Thanks for doing this.

                          Jerry
                          Every society honors its live conformists and its dead troublemakers. - Mignon McLaughlin

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                          • #14
                            If you don't mind, can you tell us what application you are using to generate these graphs?

                            Data analysis: Audacity (freeware!) - analyized @ 16384 FFT exported as text file.
                            Data plot: Gnuplot (freeware!) - a command line program, but really powerfull.

                            Here is a notepad i wrote for the gnuplot in case you will do the test

                            # gnuplot for Windows
                            # AN1-x filter analysis
                            # set output "filter3.png" # uncomment this for picture export
                            # set terminal gif small size 400,300 #uncomment this for picture export
                            set terminal windows color "Small Fonts" 7 #comment this line for pic export
                            set xrange [450:900]
                            set xtics 50
                            set xlabel "Frequency (Hz)"
                            set yrange [-48] #adjust this to fit within 24dB for 24 dB filter
                            set ylabel "Intensity (dB)"
                            plot "filter3.txt" title "24 dB filter" with filledcurves x1 3

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                            • #15
                              That one went over my pea brain. How would putting it after the effects chain make it useful? Kinda like a warm pre-amp on a mixing board, do you mean?

                              It would give you one of the sickest effects you can imagine. Endless delays, reverbs, massive wall of distorted sounds, pulsating and screaming with resonance, apply the filter and gently cut away high overtones while delay is still in the endless loop. You would have a true loop system, when you remove the dry signal from the delay, feedback is gone, so you have that endless delay texture that you can realtime modify by altering the cutoff, applying high pass and injecting more fresh sound in. Or apply two LFO's to do it instead of you, leave it in near self oscillation position, go for the dinner, come back to see what came up. You can record the whole Pighood style album that way, without even touching the synthesizer. (sorry Piggy, i couldn't resist!)

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