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what is a digital amp?

Discussion in 'Amps and Cabs [BG]' started by NedtheRed, Dec 11, 2002.


  1. NedtheRed

    NedtheRed

    Jun 20, 2002
    Jersey....eew
    Hi, im interested in buying a Peavey DPB (300w), and it says that its a digital amp. What exactly does this mean? Will the sound be any better or worse?

    Does anybody happen to know anything about this specific amp?
     
  2. VicDamone

    VicDamone

    Jun 25, 2000
    Well...I'll try. A digital power amplifier has a digital output section. Instead of the tubes or transistors moving current up and down to match the musical signal at the input side of the amp, a digital amp uses transistors or Mosfets in either an on or off state. While this is not a new idea, getting the devices to switch quickly enough to smooth out the digital corners is a result of todays high speed processing and, frankly a great deal more (design).

    The benifits are a huge reduction in heat which translates into a much more efficient amplifier. A typical AB amp is maybe 50% efficient with 50% going up in heat and the other 50% giong to your speaker. A digital amp is 90-95% efficient so you have more volts going to your speaker.

    Beware, there are digital amps whose input sections are digital which seems to qualifiy them as digital. Their output sections are still anologue.

    Currently the only domestic digital pro audio amp I'm aware of is the Carver-Pro ZR1600 which plays MUCH louder than it's output rating because its not compressing.

    As a result of processing power this is new stuff. If your not in the need of an amp soon I'd recomend waiting a year or two. I'm sure many manufactures are scrambling with this new technology. I can't imagine what the car audio manufactures are giong through right now.
     
  3. geshel

    geshel

    Oct 2, 2001
    Seattle
    A digital power amp (or PWM, pulse-width modulation, also known as Class D) works by turning the output devices (transistors) on and off very rapidly. The "on" voltage is the full-power output voltage. The actual output power is determined by how long the transistors are "on" compared to how much they are off.

    For example, if you were to switch the transistors on once every microsecond, leaving them on for half a microsecond each time, the output power would be 50%.

    As the input signal changes voltage, the "on" time of the output transistors goes up or down accordingly. Even though the output is jagged, it is smoothed out by passing it through a filter before the speakers. Theoretically, it's perfectly possible to recreate the input signal exactly (though amplified) this way.

    The Acoustic Image Clarus amp uses this technology too.
     
  4. Are Stewart amps considered DIGITAL????
     
  5. And Walter woods, as well?
     
  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.
    Technical Communications Developer, QSC Audio
    IMHO, Class D (PWM) output sections aren't really digital unless their signals are actually derived numerically. Simply converting an analog signal into PWM through the usual means isn't digital. Converting a digital audio stream into PWM, if the audio data is used to compute the duty cycle of the pulse stream, is.
     
  7. Stu L.

    Stu L. Supporting Member

    Nov 27, 2001
    Corsicana, Texas
    Are digital amps stable? What I mean is, a guitar playing buddy of mine was left standing at a gig after his new "digital" amp blew. The one time he didn't bring his back up. I guess I'm just a little cautious.(sp?)
     
  8. "As the input signal changes voltage, the "on" time of the output transistors goes up or down accordingly. Even though the output is jagged, it is smoothed out by passing it through a filter before the speakers. Theoretically, it's perfectly possible to recreate the input signal exactly (though amplified) this way. "

    How is the ON TIME of the transistor governed? Is it set by a microprocessor (digital) or by some analog means?
     
  9. geshel

    geshel

    Oct 2, 2001
    Seattle
    I'm not sure - I'd like to know too.
     
  10. I enjoyed your "My Rig" link. What do you do with that chapman stick?
     
  11. geshel

    geshel

    Oct 2, 2001
    Seattle
    Thanks. Mostly, it's just collecting dust these days. I'd sell it but I know if I did I'd immediately need/want to play it. I play it once every couple of months - mostly King Crimson stuff, though guitar parts on the melody side (Discipline-era). Since I started playing guitar I pretty much split my time between bass and guitar. I like tapping, and I'd like to get an 8-string Warr, but given that and I don't know how I'd want to tune it, it doesn't make much sense to get one now.
     
  12. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    Peavey has a good explanation on different types of power amps at:
    http://www.peavey.com/support/technotes/poweramps/classact.cfm

    Several music equipment manufactures selling "digital power amps" are refering to amps that use switching power supplies as well as Phase Modulation. Some "digital guitar amps" are just amps with digital effects built in.

    The best part of digital power amps is that you get a large amount power for the weight and very little heat. I use digital poweramps for my bass rig (and PA) because they are light and I like alot of deep low bass (which requires alot of power).
    In my opinion, digital power amps sound "colorless" when compared to a solid state of the same power rating. This can be seen as a disadvantage as the "coloring" of an amp is typically what one is after when one purchases and amp. Tube amps even have more "color" than solid state amps. For example - tube amps sound warmer because the tubes will apply different amounts of gain in different frequencies and have certain amounts of compression. Find a site that sells different types of tubes and there will be descriptions of the "sounds" that a particular tube has.
    I have "digital" power amps from 3 manufactures - Peavey, Stewart and Soundtech. I would not recommend the Soundtech (PS802) but I would recommend the Peavey DPC series.
     
  13. VicDamone

    VicDamone

    Jun 25, 2000
    I agree. Although in my brand new 'Hybrid Digital' (Jfet input stage and absolutly no filtering) the output is by far the best I and many other have heard.
     
  14. 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.
    Technical Communications Developer, QSC Audio
    Do you mean pulse width modulation?

    IMHO, calling amps with switch-mode power supplies or PWM output sections "digital" is misleading. I know, there are a lot of speaker and headphones labeled as "digital," but they're just as non-digital as the amps are.
     
  15. I was reading this older thread, because I'm looking for a 1U-rackspace poweramp.

    What's wrong with the Soundtech PS802???