From: geoff@nospamgeoffwood.org   
      
   On 17/09/2025 8:26 pm, Liz Tuddenham wrote:   
   > Geoff  wrote:   
   >   
   >> On 16/09/2025 8:23 pm, Liz Tuddenham wrote:   
   >>> Geoff  wrote:   
   >>>   
   >>>> On 16/09/2025 7:25 am, Liz Tuddenham wrote:   
   >>>>> Scott Dorsey  wrote:   
   >>>>>   
   >>>>>> Liz Tuddenham  wrote:   
   > [...]   
   >   
   >>>>> The only system that seemed to do it really effectively and in real time   
   >>>>> was Cedar: it claimed to synthesise a 'gap-filler' from the Fourier   
   >>>>> transform of the sound before and after the click.  Even that wasn't   
   >>>>> really intended to handle the continuous crackle of some of the worst   
   >>>>> gritty solid stock material (particularly inter-wars U.K. HMVs).   
   >>>>>   
   >>>>> I wondered if some sort of resonator could 'ring' and fill the gap, but   
   >>>>> it would need quite a lot of them to cover the whole audio band.   
   >>>>> Octaves seemed the logical way to go but that involved either a large   
   >>>>> number of ferrite pot cores or a lot of op-amps in state-variable   
   >>>>> filters.  I tried the pot-core approach many years ago and gave up   
   >>>>> because it was becoming too unweildy.   
   >>>>>   
   >>>>> This time I opted for state-variable filters and my design finished up   
   >>>>> with 170 op-amps and several other I.C.s.  It was a bit of a gamble   
   >>>>> whether it would be worth building it, as the principle was untested, as   
   >>>>> far as I knew.  It has paid off, the results are stunning; as the   
   >>>>> sensitivity is increased, the crackle just fades into the background and   
   >>>>> the music comes through absolutely unaffected.   
   >>>>>   
   >>>>> There are still a few things that need attention, as I can hear residual   
   >>>>> artefacts at a very low level - but I exhibited it to a group of   
   >>>>> gramophone enthusiasts at the weekend and they were completely bowled   
   >>>>> over by the sound quality.   
   >>>>   
   >>>> Isn't this all now trivial to do, better, in software ?   
   >>>   
   >>> In real time?  In a portable record player?   
   >>   
   >> OK, I missed the 'real time' bit.   
   >>   
   >> But wonder what the circumstances are for real-time. Demonstration of   
   >> vinyl (or shellac !) playback for historical or sentimental purposes ?   
   >   
   > Shellac* (what's this 'vinyl' of which you speak?)  Mainly to accompany   
   > live presentations on singers, musicians and other performers of the   
   > past - and for entertainment in the evenings after the presentations.   
   >   
   > The original purpose, which has now become secondary, was to be able to   
   > take the playing equipment to collections of recordings which were too   
   > valuable to transport to a studio.   
   >   
   > Something which I hadn't realised until recently, is that people are   
   > finding it allows them to hear subtleties on the records in their   
   > collection which they never heard before.  It might be useful to loan or   
   > hire out as a standalone analysis tool because it gives the ability to   
   > just  pop on a record and audition it quickly without a lot of faffing   
   > about with digital computers.   
   >   
   >   
   >   
   > *   In the UK, particularly during the1930s, the 'shellac' material used   
   > by the biggest group of record companies was appalling.  If you have   
   > never heard a British inter-wars HMV pressing you can have no idea of   
   > just how terrible the sound was.  Ordinary de-clickers which are   
   > designed to deal with occasional scratches on vinyl discs or good   
   > quality American or Australian shellac pressings simply cannot cope with   
   > it   
   >   
   >   
      
   But surely the Kellogs factor is a main attraction ;- )   
      
   --   
   geoff   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)