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Low Frequency EQ: Shelf or Peak?

Discussion in 'Amps and Cabs [BG]' started by rumblinbass, Jul 26, 2012.


  1. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    Anybody out there prefer peak over shelf (or Baxandall) for Low Frequency EQ?

    I was doing some listening the other day for a project I am working on and I think I prefer Peak EQ for the lows. Just seems to add what I want without too much boom and mud. A cleaner more focused low frequency boost.

    Anybody agree? Why or why not?
     
  2. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    I like peak on lows and shelving on high. A lot of graphic EQ's are set up that way. Like you said it helps to avoid mud.
     
  3. wcriley

    wcriley

    Apr 5, 2010
    Western PA
    Depends entirely on how wide the peak is and what the center frequency is.
     
  4. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    +1.
     
  5. Freight Train

    Freight Train Earth-based Alternative Scientist, Sex Researcher

    Feb 25, 2012
    Dallas, Texas
    Depends on what you're wanting to do. I find low shelves are best for cutting lows. Peak/dip is more surgical for boosting, especially if it has a sweep, so as you say you're not boosting frequencies below what you're wanting to affect. Also if the room has some low resonance that you're having to compensate for, the dip will let you dial in and cut that without losing all of the lows.
     
  6. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    hmm. good to know. wasn't aware of that.
     
  7. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    Look at any of the stompbox GEQ's. Peak on 60 Hz and shelving on 8k (or 16k depending on how many sliders you've got).
     
  8. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    using a peak EQ for low frequencies might lessen the need (in some cases) for a high pass filter.
    ...maybe?
     
  9. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    The first question you need to ask yourself is:

    "Do I want precision or idiot proof-ness?"

    Then we can figure out what'll work best for your needs.

    Please tell me Rupert wants to build a bass preamp. I would love to buy that man a beer and talk gear.
     
  10. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    um, no.
    but what if I told you that I am designing a bass preamp with some of those vintage ideas and methods in mind?

    edit: Rupert is more of a Bourbon kind o' man...
     
  11. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    Transformer coupled HV discrete opamps?

    Sign me up!
     
  12. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    not planning on HV...but not completely ruled out. JFET input gain stage makes HV rails difficult. JFET's aren't typically rated for more than 40V. Right now I am planning on using the 2SK170.
    Discrete amplifiers? Yes. Not the Ring-of-3 type he used way back in the day but another topology that shows a lot of promise. Ultimately the goal is a low open-loop gain amplifier.
     
  13. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    Transformer coupled?
    ...um, looking for a 1M input Z. Kind of rules out a traditional input transformer circuit. However, doesn't rule out the current circuit we use for Mic Pre's. I do plan on a transformer coupled output stage for DI out.
     
  14. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    Sorry...I threw transformer coupled in at the last minute. It's on my mojo preamp wish list.

    I'd love to see what you come up with. I've had so many ideas I though were winners just to realize someone else already does it (or did it 30 years ago) and that some things are just outside my range of abilities.
     
  15. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    For low open loop gain I prefer CMOS chips. They've been used quite effectively in bass preamp designs (and they're cheap!).

    I'm just getting my feet wet on discrete amplifiers. I finally work up the nerve to start messing with JFET's and they stop making them!
     
  16. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    noted.
     
  17. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    I should really finish my thoughts before I hit send.
     
  18. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    The big plus to CMOS is that it's basically an FET amplifier with nice "tubey" break up if you keep the gain low enough. They're only good up to about 40dB but if you're input signal is too hot they can get just as thrashy sounding as regular opamps.
     
  19. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    frequently guilty of the same thing :rolleyes:
     
  20. rumblinbass

    rumblinbass

    Aug 22, 2003
    Wimberley, TX
    guess I should start investigating CMOS circuit then...

    edit: can you recommend any suitable for audio?
     

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