Perceived loudness question; 12 watts class A vs. 18 watts class AB

Discussion in 'Amps and Cabs' started by BlueHeaven, Oct 31, 2005.


  1. BlueHeaven

    BlueHeaven Member

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    Here's the deal; I was leaning toward a Fargen Mini-Plex 12 watter(s.e. class A) but played a Budda SD18 today that sounded really good. I've always heard that class A watts are PERCEIVED by the ear as louder than class AB. I'm not looking to own the loudest under 20 watt amp I can...I'm looking to be able to open the master a bit w/o making my ears bleed. This might be a stupid question but, well I'm not afraid to ask a dumb question!
    Greg:confused:
     
  2. HeeHaw

    HeeHaw Member

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    I have ran a 36 watt, 4xEL84 against a plexi and it wasn't much quieter at full bore. Me thinks this whole wattage thing is just a clean headroom measurement. Yes the 36 watter broke up alot faster and sounded killer, but was still closing in on being nearly loud as the plexi RI.:confused:
     
  3. bob-i

    bob-i Member

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    A watt is a watt... period

    Perceived loudness is a combination of volume and fullness/harmonic complexity.

    Typically 12 to 18 watts is hard to perceive a difference. Between Class A and Class A/B you'll typically hear Class A as a little richer, but of course there are other factors like preamp and speaker.

    Bottom line, you'll need to A-B the amps and see. Both will be loud.
     
  4. rebob

    rebob Member

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    according to guitarone mag.(nov.'05 issue) in their review on the class A Mesa Lone Star Special . . . "a 30 watt class A amp will stand up favorably to a 50 or 100 watt class A/B amp."

    i haven't tested this but i have a Lone Star Special and it's Very loud. even at 5 watts!

    rebob.
     
  5. drbob1

    drbob1 Silver Supporting Member

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    Plus there's the whole issue of how you measure watts. Some companies measure clean output in RMS watts, others measure total possible output. It can get very confusing-generally a Fender rated at 50w will be quite a bit louder than a Marshall rated at 50w, until you push them both into distortion, then the Marshall may be louder. There's also a factor of the power amp compression-using a Vox AC30HW as an example, it's significantly louder clean than a Pro Reverb or a 50w Marshall combo with G12H30s but when you crank them all, the AC30 doesn't get a lot louder, while the Marshall and Fender do (they're all ear bleedingly loud in a medium room). Plus there's speaker efficiency-there can be a 6 dB difference in sensitivity between a pair of speakers which would make a 12w amp the same volume as a 50w amp with the same circuit type. I don't think class A vs class AB is much of a directive to help you decide (especially since most class A amps aren't).
     
  6. JamesPeters

    JamesPeters Member

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    It will vary from amp to amp based on a lot of things.

    I've heard the miniplex and it can be somewhat loud, although I'd say the Budda would probably be somewhat louder (unless they're using a small output transformer).
     
  7. BlueHeaven

    BlueHeaven Member

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    I appreciate the responses. I sure wish I could a/b these amps...not just for volume but for tone and feel. The bad thing is, the Mini-Plex may be THE amp for me(I don't know) but the Budda I've played and liked alot. I guess if I had y'all's money I'd just buy 'em both!;)
     
  8. Rusty G.

    Rusty G. Member

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    I've got a Fargen Mini-plexi combo with a 12" Weber Blue Dog. I run it in the half power mode, crank the master all the way open and run the pre-amp at about 3:00 o'clock. I play a '57 re-issue Les Paul into it and use the volume on the guitar to clean it up.

    It's not ear bleeding loud. Now, I want to add this. I like my Blue Dog speaker. . .but, I don't find it to sound great in the full power mode. In particular, the bass frequencies start to "fart" out. But, in the half power mode, it doesn't get flabby and it sounds great. Not sure if it's a 15 watt speaker or what, but it's just my observation that the amp sounds best in half power mode into that speaker. Haven't had the chance to try other speakers. I think I'd like to try a Scumbag G12H for something different.

    f.w.i.w. . .I don't find the Mini-plexi to be really loud. You could gig with it, but you'd need to mic the amp. Not sure that it would have enough head room to play over a loud drummer. With that said, it's a great sounding amp that's easy to get a great sound with and easy to record.

    Good luck!
     
  9. tacorivers

    tacorivers Silver Supporting Member

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    Is the Lone Star Special actually "Class A"? MB has been pretty loose with that term before.
     
  10. shane_m

    shane_m Member

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    Hey Blue Heaven..............I currently own a Budda SD18 and used to own a Mini Plex. I'll put it this way. I sold the Mini and have no plans whatsoever of getting rid of the Budda. Don't get me wrong the Fargen sounds great and may be a little more flexible with the tube switching and all but I found that even on the 12 watt setting it just wasn't quite loud enough. The SD 18 is almost too loud, but I find that I'm able to dial in the tone I'm looking for and more. Plus I like the two channels. This thing can go from chimey clean to absolute scream in a second.

    Shane
     
  11. HarryJ

    HarryJ Member

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    Always read that wattage vs dB was 10 to 2

    So, a 100 watt amp sounds twice as loud as a 10 watt amp

    Of course there are other factors including speaker efficiency

    HJ
     
  12. michael30

    michael30 Gold Supporting Member

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    I recently A/B'd (and A+B'd) two of my amps: a Fender Champ 12 (12W class A 1x6L6GC) and a Dynacord Twen (18W 2x6V6GT). The Fender has an efficient Fane Classic speaker while the Dynacord has the original not-so-efficient Isophon alnico speaker. The volume level was more or less the same, but the Champ had a clearer sound which would probably have sounded louder in a band situation. They sounded really good together (better than either one by itself).

    Michael
     
  13. 1964

    1964 Member

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    > 'according to guitarone mag.(nov.'05 issue) in their review on the class A Mesa Lone Star Special . . . "a 30 watt class A amp will stand up favorably to a 50 or 100 watt class A/B amp."'

    I just don't see it! That seems like a gross exaggeration to me.

    IMO, the difference between the perceived volume of a class A and class AB amp, all other things being equal (though they never are) would be quite minimal. The class A should be expected to be perceived as a little louder.

    A 30W class AB amp should compete favourably against a 60W solid-state amp, but I don't think most 30W class A amps would compete against most 100W solid-state amps.

    Of course, when solid-state amps distort it's usually harsh and horrible. Also, most solid-state amps would have cheap speakers.

    There aren't many solid-state boutique amps, and a big part of the equation would be the use of highly efficient speakers.

    For instance, Clark's 6W Lil' Bit Ltd will surprise. Not only is a 6W Champ much louder than most people realise, but through a 103dB Red Fang speaker, it's going to be as giggable as many 12-20W amps, especially vintage ones with original speakers.

    The big constraint of most small tube amps is the usual 8” speaker. Give a small tube amp a decent speaker or cab, and it will surprise.

    Clean headroom is the big question, especially with humbuckers.
     
  14. 1964

    1964 Member

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    ...Therefore, the Fargen Mini-Plex, even in 8W mode, should have plenty of output through a decent speaker or cab. And in 12W mode should have sufficient clean headroom for humbuckers.
     
  15. 1964

    1964 Member

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    IMO, the Mini-Plex should mate very well with a 1x12" cab fitted with a 101dB Eminence Private Jack (improved, more efficient, Greenback clone). YMMV. I can't speak for the Buddha.
     
  16. 1964

    1964 Member

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    > "Not sure that it would have enough head room to play over a loud drummer."

    The obvious solution is to ditch the drummer and save your hearing. :D
     

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