Class-D Power Amps | Page 2 | The Canadian Guitar Forum

Class-D Power Amps

Discussion in 'Bass' started by Hammerhands, Mar 24, 2020.

  1. jb welder

    jb welder

    Joined:
    Sep 13, 2010
    Location:
    Melonville, Canada
    But I think your 'who cares' comment extends to both bass and guitar so I have no issue with that. I just think it's funny when people make such an exception, but only for bass.
    But I'm sorry about the de-rail. This thread is (I think) about class-D vs conventional SS, rather than SS vs tube.
     
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  2. Hammerhands

    Hammerhands

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    Dec 19, 2016
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    Winnipeg
    Let us go off the rails!
     
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  3. Hammerhands

    Hammerhands

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    Dec 19, 2016
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    I think the Class-D discussion is over. With enough headroom or good design choices there doesn't seem to be any class issue. Unless someone has a contrary view?
     
  4. Hammerhands

    Hammerhands

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    Dec 19, 2016
    Location:
    Winnipeg
    What is it you get specifically from a tube amp for bass? From the power section?

    Would you say the Ampeg B-15 James Jamerson sound is the ideal?
     
  5. Hammertone

    Hammertone Gold Member

    Joined:
    Feb 2, 2006
    Location:
    Toronto
    I was at an L&M in January, and noticed that, among the various new bass heads and cabs, they had three new bass heads stacked up one above the other in one spot:
    -Mesa Subway D800 - 800 Watts @ 4 or 2 Ohms / 400 Watts @ 8 Ohms
    -Mesa Subway D800 Plus - 800 Watts @ 4 or 2 Ohms / 400 Watts @ 8 Ohms
    -Mesa Carbine 6 (discontinued in 2017 but L&M still has stock) - 600 Watts @ 4 or 2 Ohms / 320 Watts @ 8 Ohms.
    I typically buy used gear, and am not in the market for a bass head, but had some time to kill and thought it would be a bit of fun to compare them. It seemed like a good A/B opportunity for conventional older obsolete amplification (the Carbines were made from 2007-2017) versus newer Class D.

    My most "modern" bass amp is a Mesa Fathom head (same as the Carbine 6, just a different name). Mine is from 2007. I have friends who have moved to Class D bass gear, including the Subway D800, along with various Traynor, GK and Ampeg Class D bass heads. I think the new super-light, super-small amp heads are great for convenience in terms of size, weight and cost. I was simply curious to see how these three heads would sound compared to each other, all played through the same cab in the store, which was a Mesa vertical 2x15" cab, IIRC, using the same bass (stock J-bass, similar to what I play). No axe to grind, bone to pick, or pre-disposition one way or another. The only bass amp I have any sentimental feelings for is my Ampeg B-15S.

    I set up all three of the amps with similar tone/gain/volume settings, and one of the very helpful guys in the store managed the cab cable switching between heads for me. I found that there was a huge difference in sound and volume between the Carbine 6 and either of the Subways. I played around with the settings on the Subways to compensate, but the huge differences in tone and volume remained - the Carbine was really a lot better across the board. I was quite surprised by the extent of the difference. The Carbine 6 uses "Trans-Class™ Power w/8 Power MOSFET" power as opposed to Class D power. It weighs 25 pounds - hardly SVT or 400+ territory, but still way more than a 5-to-10 pound Class D bass head.

    Just a real world test - IMO, YMMV and so forth.
     
    Last edited: Mar 27, 2020 at 2:46 AM
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  6. laristotle

    laristotle Gold Member

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    Aug 29, 2019
    Location:
    acton
    My Markbass is class 'C', according to the webs. Sounds great to me. How's that fit in the alphabet of bass amps?
     
  7. Hammerhands

    Hammerhands

    Joined:
    Dec 19, 2016
    Location:
    Winnipeg
    What is that?

    Class D Amplifiers Offer Significant Advantages | DigiKey

    This is the way I understand the classes as they relate to guitar amps.

    Class A, mostly with one tube. Everything happens on the positive side, the tube is always conducting.
    Class AB, tubes are arranged in push-pull. There is a crossover area where both tubes are conducting.
    Class B, like Class AB but there is no crossover area.

    Class C seems to be like Class B, but there could be a gap where neither tube would be conducting. I'm not sure how that would work? Maybe there are transistors working in Class B and others in Class C?
     
    Last edited: Mar 25, 2020
  8. jb welder

    jb welder

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    Location:
    Melonville, Canada
    Not sure if this was directed at me, but the Jamerson sound is pretty ideal but maybe a bit muffled for me. Probably too dense foam. :)
    It's hard to put into words what exactly it is about the tube amp but part of it is probably the natural compression and lower damping factor. I have an Ampeg V-4 running in the 100 to 120W range. Not even the bass version, I just lock up the reverb tank. The kind of 'right here' clarity I just can't get with SS amps of 3 or 4 times the power output (using same cab). I don't have trouble hearing myself with the Ampeg, but usually find that to be a struggle with the SS.
    Not sure what exactly it is, but similar to how @Hammertone described the lower power linear Mesa being noticeably superior to the higher powered digital counterpart.
     
    Last edited: Mar 26, 2020
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  9. keto

    keto Gold Member

    Joined:
    May 23, 2006
    Location:
    Edmonton
    If I was there, I could have dialed the 800+ to be VERY VERY VERY close to the Carbine, it has a ton of punch and a very flexible EQ capable of cutting heads and rattling stages. You can't be afraid of the volume knob on the Subway stuff, they have a very smooooth ramp up right around the dial.
     
  10. Frenchy99

    Frenchy99

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    Oct 15, 2016
    Location:
    North Pole

    Who cares !?!? :eek:

    Bass players do and thankfully so !!! o_O

    I know this is a guitar forum but Cmon…

    :rolleyes:
     
    Last edited: Mar 26, 2020
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  11. dtsaudio

    dtsaudio Gold Member

    Joined:
    Apr 15, 2009
    Location:
    Hamilton, ON
    It most certainly is not. The distortion of a class c amp is unlistenable. It's only good for RF
    Class B does have a crossover. Distortion in that kind of amp is clearly audible at low volume.
    It's all about the bias. Class C is special purpose. Ignore.
    Class B is usable, depends on the application. You could bias a tube amp to class B and hear what it sounds like. Guitar players come pretty close anyway.
     
  12. laristotle

    laristotle Gold Member

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    Aug 29, 2019
    Location:
    acton
    Class D then? or what?
    Nothing on the MarkBass site that helps.
     
  13. dtsaudio

    dtsaudio Gold Member

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    Apr 15, 2009
    Location:
    Hamilton, ON
    One thing that needs a bit of clarifiaction here is the thinking that Markbass, Mesa Carbine, and a few others are Class D. They are not.
    They are standard Class AB (or as Markbass calls them analog amps) with switching or SMPS power supplies.
    Most of the weight of your standard solid state amp (combos excluded) comes from 3 places. The power transformer, the chassis and the heatsink in that order.
    All of these amps are fan cooled (smaller heatsink), the chassis's are cheap and much thinner, and there is no large power transformer (which is why the chassis can be thinner).
    Mesa has then taken things one step further now, and in the Subway series made Class D amps. They are even lighter and more efficient than their older amps.

    And here is where I take exception to Class D amps, whether for bass, guitar or stereo, and why I won't buy one.
    Reliability AND repair-ability in the long run.
    I can fix almost any guitar or bass amp that uses the standard technologies. If factory parts aren't available, then retrofits can usually be made, and you're back in business.
    When it comes to class D, the amps are usually not repairable, or not worth repairing becasue the amp modules are so inexpensive it is cheaper to replace than repair.
    So what happens when you are playing your 6 or 7 year old Class D amp and it craps out. The manufacturer says "we don't make it anymore and there are no parts. Can't help you"
    Guitar amp manufactures are not like car makers. They're not obligated to keep a stock of old parts.
    You can flame away on this. But I have already seen this happen to more than one person, and on some very expensive gear.
    And to take things up one more notch. My 6-7 years is the design life span for most digital products.
     
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  14. Hammerhands

    Hammerhands

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    Dec 19, 2016
    Location:
    Winnipeg
    Class D amps / Compact Bass heads

    "Hi David...The Little Mark II amp is class AB.

    Best Regards
    "
     
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  15. Hammerhands

    Hammerhands

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    Dec 19, 2016
    Location:
    Winnipeg
    I did no such thing.
     

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