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HPF-Pre DIY

Discussion in 'Amps, Mics & Pickups [DB]' started by ricobasso, Aug 28, 2012.


  1. ricobasso

    ricobasso

    Jan 18, 2007
    UK, South East
    I've just read the HPF-pre review thread and am thinking of building one to see how it works for myself. I'd be interested to hear from fdeck what the reason was for his decision to use discrete components. Is there some magic in the way it limits compared to some very nice rail-to-rail opamps out there?
     
  2. Nicer saturation, more headroom, less noise, I think.

    You should read all of FDecks web pages, he explains it there.
     
  3. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    The Series 3 is op-amp based. There are some op-amps out there with excellent specs and I trust Francis to know which ones to pick.
     
  4. ricobasso

    ricobasso

    Jan 18, 2007
    UK, South East
    I have an Ashworth piezo pickup on my upright and I've been using my own design of pre-amp for a long while now. It is a simple buffer with 10M input impedance and a bit of gain (no HPF and no polarity switch). It uses one TS912 dual opamp. This device can swing rail-to rail and has a max quiescent current of 400uA. This would give over 600 hours idling with a 250mAh battery. I've been very happy with it and have received many good comments over the years about my sound.

    So....before I build another preamp......if there's a good reason to abandon the TS912 for a discrete design, I'd like to find out more. If the series 3 uses opamps then I guess not, but it would be nice to hear fdeck's thought on the subject.
     
  5. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    I've used high-quality op-amps in laboratory audio applications for many years, including in circuits of my own design.
     
  6. iiipopes

    iiipopes

    May 4, 2009
    From the time I was 14 years old and got my first Sears electric guitar in 1975 and "looked under the hood" to see how it worked, I've tinkered with everything. At a point a few years ago, I finally decided that occasionally there were items that in spite of my tinkering, were more cost effective to just own. The fdeck series 2 is one of those. With my Full Circle, it does absolutely what I need for buffering in both level and cutoff, with excellent noise and linearity characteristics, before my signal hits my amp. Just drop the $70 and be done with it. I did, and with my current limitations of both time and money, I could not have built a better unit.
     
  7. ricobasso

    ricobasso

    Jan 18, 2007
    UK, South East
    :rollno: I'm in the UK
     
  8. seang15

    seang15

    Aug 28, 2008
    Cary NC
  9. drurb

    drurb Oracle, Ancient Order of Rass Hattur; Mem. #1, EPC

    Apr 17, 2004
    PM sent.
     
  10. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    Only remotely related: I have a DIY simple buffering pre also designed by Francis in my EUB. At the time it made for a big improvement in sound. Now I also own a Fdeck HPF for my DB. Last week I took the time to A/B the EUB with the buffering pre and the HPF. The HPF is yet another step up. That's not only because of the filter, it is also more pleasantly voiced (or the lack of voicing) and handles dynamics better. I'm yanking out the old pre and am going to use the HPF for the EUB too.
     

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