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Latest build

Discussion in 'Effects Pedals, Strings and more' started by mhammer, Nov 25, 2019.

  1. mhammer

    mhammer

    Joined:
    Nov 30, 2007
    Location:
    Ottawa, Ontario
    Some of you may be familiar with the old Maestro FSH-1 Sample and Hold. Great pedal, though a rather niche market. Unfortunately it depends on a chip which is now out of production. Fortunately, one of the folks on the DIYStompbox forum adapted the circuit to a currently-available chip, and in a blessedly smaller package (it was a big'un) ( https://www.effectsdatabase.com/model/maestro/fsh1# ).

    For the uninitiated, a sample & hold takes "snapshots" of the momentary voltage from a noise source, and "holds" it until instructed by a clock to take the next sample/snapshot. Because it's a noise source, each snapshot is generally different from the previous one in unpredictable ways. The sampled voltage is then used to set the resonant frequency of a filter, which will bop around unpredictably. This also depends on the quality of the noise source. While the particular transistor type used as the noise source is actually a pretty common one, you need to "audition" them for noise characteristics, since those vary from unit to unit, even within the same manufacturer and lot number.

    The adapted circuit is actually a reduced version of the original. On the original, you can see a slider switch that says "Filter Sample/Hold". In the Filter setting, the unit behaves like a fairly normal envelope-controlled filter (autowah). The adapted circuit skips that and concentrates on the S&H part only, which allows it to be smaller.

    I etched the board that the fellow generously prepared a layout for and posted, made a few mods, and the demo video is below. The sound is lousy because I didn't turn down the mic sensitivity enough. BUt apart from that, you'll hear the range of things it can do. The controls are labelled SPD (how quickly it progresses from sample to sample), RNG (the degree of contrast between samples permitted), BIAS (tunes the filter to higher or lower frequency ranges), RES (sets the degree of emphasis around the resonant frequency of the filter) and a toggle marked DROOP.

    The DROOP function is something I think I may have originated. Normally, the filter operates in steps. (Some other pedals have used a S&H effect and often labelled it "stepped") It gets to sound like a step because the sampled noise voltage is held onto by a storage capacitor in a stable manner. The droop function provides a way for that capacitor to actually drain off before the next sample is taken, such that each step is a kind of mini-sweep. It's a different sort of effect. There are times and settings when it reminded me a lot of the theme "Tillicum" by Syrinx, from that old CTV show "Here come the '70s".

    The effect is limited in its usefulness, much like a ring modulator, or even an octave divider. But it's a neat effect.

     
  2. KapnKrunch

    KapnKrunch Gold Member

    Joined:
    Jul 13, 2016
    Location:
    Yes
    Very sci-fi! What could it be used with other than guitar?
     
  3. mhammer

    mhammer

    Joined:
    Nov 30, 2007
    Location:
    Ottawa, Ontario
    I suppose anything that sustains long enough to hear the filter bubble around. So keyboards are fair game.
    Sample-and-hold IS a synth module, historically. Adapting it to guitar was the more recent development.
     
  4. KapnKrunch

    KapnKrunch Gold Member

    Joined:
    Jul 13, 2016
    Location:
    Yes
    Yeah, I was thinking maybe the EuroRack crowd had sonething like this going on...

    How about a Theremin!
     
  5. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    My son-in-law would love this effect. Sounds like a lot of fun.
     
  6. mhammer

    mhammer

    Joined:
    Nov 30, 2007
    Location:
    Ottawa, Ontario
    I can't imagine he DOESN'T have this by now. As off-the-beaten-path as S&H is for guitar, it is about as de rigeur for synth players as a phaser or EQ pedal is for guitar players.

    But even if he has one, I'll wager he doesn't have it set up for "droop". I'll have to pop him a note and hip him to the idea.
     
    greco likes this.
  7. CathodeRay

    CathodeRay

    Joined:
    Jan 12, 2018
    Location:
    Toronto
    Pete Townshend through an ARP2600 voltage controlled filter / sample & hold.

     
    Last edited: Nov 26, 2019
    mhammer likes this.
  8. mhammer

    mhammer

    Joined:
    Nov 30, 2007
    Location:
    Ottawa, Ontario
    Well there you go. You CAN use it in rock.
     

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