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Re: [Doepfer_a100] Re: A-107 outputting noise.

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  • Florian Anwander
    ... I don t own a A_107, but I even could imagine, that this is the normal noise level at certain filtersettings. Especially if high pass filters are placed as
    Message 1 of 10 , Feb 14 1:39 AM
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      On 13.02.13 22:17 , isoldeandisobelle wrote:
      > Here is the soundcloud link - https://soundcloud.com/isolde-and-isobelle/a-107
      >
      > First with a sawtooth and then just the filter out as I turn through the filter presets....it is also more noticeable with something like a sine.
      I don't own a A_107, but I even could imagine, that this is the normal
      noise level at certain filtersettings. Especially if high pass filters
      are placed as last part of the filteralgorithm. Dieter may jump in here.
      Perhaps the bandpasses are generated using LP->HP instead of HP->LP.

      Florian
    • isoldeandisobelle
      Well, Ok, Thank you for your reply. If you say this is a normal level for this unit, then that is fine with me, I did not want it to be a fault that became
      Message 2 of 10 , Feb 14 9:08 AM
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        Well, Ok, Thank you for your reply.

        If you say this is a normal level for this unit, then that is fine with me, I did not want it to be a fault that became progressively louder within time.

        Best wishes to all and thanks again for your advice.
        --- In Doepfer_a100@yahoogroups.com, Florian Anwander wrote:
        >
        > On 13.02.13 22:17 , isoldeandisobelle wrote:
        > > Here is the soundcloud link - https://soundcloud.com/isolde-and-isobelle/a-107
        > >
        > > First with a sawtooth and then just the filter out as I turn through the filter presets....it is also more noticeable with something like a sine.
        > I don't own a A_107, but I even could imagine, that this is the normal
        > noise level at certain filtersettings. Especially if high pass filters
        > are placed as last part of the filteralgorithm. Dieter may jump in here.
        > Perhaps the bandpasses are generated using LP->HP instead of HP->LP.
        >
        > Florian
        >
      • Florian Anwander
        ... I don t know whether it is normal! I do not own a 107. But, I can *imagine* that it is normal.
        Message 3 of 10 , Feb 15 2:42 AM
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          Am 14.02.2013 18:08, schrieb isoldeandisobelle:
          > If you say this is a normal level for this unit, then that is fine with me,
          I don't know whether it is normal! I do not own a 107.

          But, I can *imagine* that it is normal.
        • isoldeandisobelle
          Thank you for your replies Florian, perhaps Dieter will have the definitive answer.
          Message 4 of 10 , Feb 15 6:20 AM
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            Thank you for your replies Florian, perhaps Dieter will have the definitive answer.

            --- In Doepfer_a100@yahoogroups.com, Florian Anwander <fanwander@...> wrote:
            >
            > Am 14.02.2013 18:08, schrieb isoldeandisobelle:
            > > If you say this is a normal level for this unit, then that is fine with me,
            > I don't know whether it is normal! I do not own a 107.
            >
            > But, I can *imagine* that it is normal.
            >
          • ddoepfer
            ... I don t know the definitive answer but indeed the XP filter design generates a bit more noise than other filters (the A-107 is nothing but an expanded XP
            Message 5 of 10 , Feb 15 6:38 AM
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              > Thank you for your replies Florian, perhaps Dieter will have the
              > definitive answer.

              I don't know the "definitive answer" but indeed the XP filter design
              generates a bit more noise than other filters (the A-107 is nothing but an
              expanded XP filter). The reason is that the original signals of the four
              filter stages (CEM3379 filter chip) have very low levels and have to be
              amplified by about 100 to obtain the audio level used in the A-100. This
              causes a higher noise floor because even the noise is amplified. And in
              addition some filter types are composed from up to 4 filter stages. This
              increases the noise additionally. The filter types that use only one filter
              stage (i.e. 6, 12, 18, 24 dB low pass) should be a bit less noisy because
              for these only one of the filter stages is used.

              But with max. audio input level (i.e. just before clipping) the noise floor
              should cause no problems.

              Best wishes
              Dieter Doepfer
            • isoldeandisobelle
              That is definitive enough for me, thank you very much. Yes, it is not too much of a problem, as with higher inputs the noise is all but suppressed or masked
              Message 6 of 10 , Feb 15 11:19 AM
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                That is definitive enough for me, thank you very much.
                Yes, it is not too much of a problem, as with higher inputs the noise is all but suppressed or masked and with the filter types you mentioned it is not at all so bad, only in the quieter passages that I may create does it become a bit of an issue, but then I tend to just use another filter module for those parts.

                I was only concerned that it may have been a fault that may have got progressively louder over time.....but, your answer puts that worry aside.

                Thank you again and best wishes.
                --- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:
                >
                > > Thank you for your replies Florian, perhaps Dieter will have the
                > > definitive answer.
                >
                > I don't know the "definitive answer" but indeed the XP filter design
                > generates a bit more noise than other filters (the A-107 is nothing but an
                > expanded XP filter). The reason is that the original signals of the four
                > filter stages (CEM3379 filter chip) have very low levels and have to be
                > amplified by about 100 to obtain the audio level used in the A-100. This
                > causes a higher noise floor because even the noise is amplified. And in
                > addition some filter types are composed from up to 4 filter stages. This
                > increases the noise additionally. The filter types that use only one filter
                > stage (i.e. 6, 12, 18, 24 dB low pass) should be a bit less noisy because
                > for these only one of the filter stages is used.
                >
                > But with max. audio input level (i.e. just before clipping) the noise floor
                > should cause no problems.
                >
                > Best wishes
                > Dieter Doepfer
                >
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