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Class D Power

Discussion in 'Amps [BG]' started by EZ9R, Dec 31, 2013.


  1. EZ9R

    EZ9R

    Oct 28, 2008
    I was trying out some basses today at a local store and was using a GenzBenz Shuttle 6.0 through a single 12" cab. The salesman said I should turn the master all the up max and use the gain as the volume control because "It's a Class D Head".
    He said turning the master below max or 10 attenuates the power. I'm used to dialing in my gain just before clipping and using my Master as the volume on my MB SD1200. Any opinions? Thanks.
     
  2. B-string

    B-string Gold Supporting Member

    The salesperson was completely clueless and you can run it either way to your preference.
     
  3. 1958Bassman

    1958Bassman

    Oct 20, 2007
    Level controls DO attenuate- that's the reason most have a scale of dB that shows 0dB at WOT and -∞ at the low end of the control.

    How the controls are set up depends on the intended application- many pro audio amplifiers have unity gain at some middle position and +4dBu at a higher position, which is standard level for pro, balanced audio, but -10dBu is standard for consumer audio, unbalanced HighZ equipment. Instrument amps are a toss up.

    To the OP- using the Master level control as the volume control is backward. The Master is to set the maximum clean level, with the input level control used to adjust for the application.
     
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Disclosures:
    Technical Communications Developer, QSC Audio
    Sales guys usually don't know how anything works. You found a prime example. If the master was always supposed to be turned up all the way, there wouldn't be a knob there.
     
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  6. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Disclosures:
    Technical Communications Developer, QSC Audio
    Unity gain (Vout = Vin) on most pro power amps would have the gain control turned almost all the way down.
     
  7. B-string

    B-string Gold Supporting Member

    I disagree with an instrument amp, if your aim is to saturate the level in the preamp (many instrument amps "sound" better this way with harmonic distortion and compression) then it is not "backwards".
    As Bob Lee points out if it was not to be used, it would not be there.
     
  8. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Disclosures:
    Technical Communications Developer, QSC Audio
    Good point.
     
  9. Geri O

    Geri O

    Sep 6, 2013
    Florence, MS
    Quote:
    Originally Posted by B-string
    I disagree with an instrument amp, if your aim is to saturate the level in the preamp (many instrument amps "sound" better this way with harmonic distortion and compression) then it is not "backwards".

    True, although saturating the preamp of a bass amp has never been a goal of mind. I'm usually in the middle of two guitar players, there's enough purposeful distortion going on without my help.

    Geri O
     
  10. EZ9R

    EZ9R

    Oct 28, 2008
    I just never heard that before about class D power. This wasn't a GC salesman either. That's why I was curious.
     
  11. B-string

    B-string Gold Supporting Member

    Note I didn't say overdriven, a degree of saturation warms the signal up and can help cut through the chainsaws on glass.
     
  12. B-string

    B-string Gold Supporting Member

    Class D is no different than class A, A/B, G or H in this respect.