MT 15

Discussion in 'Amplifiers' started by RedGuitars, Jan 23, 2018.

  1. Michael_DK

    Michael_DK New Member

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    With everybody talking about how loud this thing is, I'm starting to think this amp is not for me and my bedroom playing.... :(
     
  2. elvis

    elvis Hamfisted String Banger

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    I use my Archon 100 at home levels. I'm sure the mt15 will do it.
     
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  3. DreamTheaterRules

    DreamTheaterRules New and improved member

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    Yes, same with the 50.
     
  4. Tone-y

    Tone-y New Member

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    For those talking about its loudness for only a supposedly 15 watt amp, don't forget that volume works on a logarithmic scale. For twice the volume you need 10 times the power! To get twice as loud as a 15 watt amp, you'd need 150 watts. For twice as loud as a 50 watter, you'd need a 500 watt amp!

    In other words, this is potentially only half as loud as a 150 watt amp.
     
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  5. jfb

    jfb Plank Owner

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    I didn't take time to play one at Experience. I might order one. I remember liking the Archon when I played it.
     
  6. shinksma

    shinksma What? I get a title?

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    So I had a good discussion with one of the guys at the amp-display area on the factory floor at Experience 2018.

    He stated that the MT15s should arrive at PRS this week, and ship out to dealers by next week.

    The most recent delay was unavailability of a specific part at the overseas factory - not obsolete parts, just not available to them from their suppliers. So PRS sent parts from the US to the overseas factory, rather than doing a design tweak to use an alternate but not ideal part. He didn't indicate what the part was (for good reason, I suspect).

    I know folks are getting antsy for these things, but look at it this way: again, PRS did not compromise, you are gonna get one heck of an amp!

    I know I will pick one up eventually. Maybe after the DG30, maybe before. (Again, I would say don't tell my wife, but she already knows...)
     
  7. LSchefman

    LSchefman Hears Tones

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    I’ll bet it has a volume control right on the front panel somewhere. :)
     
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  8. elvis

    elvis Hamfisted String Banger

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    I had my volume control modded to an area control. Just one derivative...
     
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  9. DreamTheaterRules

    DreamTheaterRules New and improved member

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    My Archon is fitted with a dB meter. The sensor is mounted two rooms away... usually in the living room and on the couch while I’m playing.
     
  10. Em7

    Em7 deus ex machina

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    Actually, the multiplier is 8, not 10. A 120W amp is twice as loud as a 15W amp. It takes a 9dB increase in sound pressure for the human ear to perceive something as twice as loud. Sound pressure increases by 3dB every time we double power; therefore, we are looking at 2 to the 3rd power. Inversely, it takes an 9dB reduction in sound pressure for the human ear to perceive something as half as loud. If we want to reduce volume to that of 1/8th of a 100W amp, we need to reduce sound pressure by 27dB, which is equivalent to dividing power by 512 (2 raised to the 9th power). A 0.2W amp is 1/8th as loud as a 100W amp.

    One thing that needs to be understood is that the average guitar speaker produces 100dB @ 1W @ 1 meter.

    dB = 10 * log10(power)

    Therefore, we have the following sound pressure levels are different wattage levels

    100 + 10 * log10(1) = [email protected]
    100 + 10 * log10(2) = 103dB @2W
    100 + 10 * log10(4) = [email protected]
    ...
    100 + 10 * log10(15) = 111.76dB15W
    ...
    100 + 10 * log10(100) = [email protected]

    The human voice at three feet is 65dB. Needless to say, a 1W amp at full tilt through a loudspeaker with an efficiency of 100dB @ 1W @ 1 meter is significantly louder than the human voice. I love tube amps as much as the next guitarist, but, in my humble opinion, bedroom playing is best handled by a quality fully analog solid-state setup or a digital signal processor combined with a solid-state power amp. We are dealing with a compromise situation where we want to achieve the best possible performance at the lowest possible volume. Solid-state circuitry is more linear and allows for a finer level of control over signal shaping. The beauty in a tube amp lies in how the power section pushes back at you when run at full tilt. This phenomenon is due to poor power amp damping and back EMF from the speaker. While I use a tube amp when I jam somewhere where I can open it up, I use a Tech 21 Trademark 60 at home. There are different tools for different jobs.
     
    #490 Em7, Jun 14, 2018
    Last edited: Jun 14, 2018
  11. Tone-y

    Tone-y New Member

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    Obviously my laymans explanation was a bit rough. Thanks for your the clarification; very interesting.
     
  12. DreamTheaterRules

    DreamTheaterRules New and improved member

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    I bought into all that for a while. In fact, for years I couldn't get away with playing with much volume at home, so I spent all my money on guitars and modelers and didn't have any great amps. Unfortunately, I tried numerous different SS and modeling devices, and NONE has EVER sounded as good as my Archon, or ATMA or Mark V25 or Mark V, or Custom 50 or 2 Channel H, or Vox AC30hw2x, or Mini Rec, or TA15 or TA30 etc.... So I'm back to Every single time I'm playing and my wife is awake or not home, I use a tube amp. The only time I turn on my AmpliFire or small SS amps, is after she's in bed.
     
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  13. Em7

    Em7 deus ex machina

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    There is nothing wrong with using a tube amp at home as long as you can let the power amp breath a little bit. I own a 2-Channel "H" (I have also designed and built tube amps at several power levels), and it in no way performs as well as the Tech 21 Trademark 60 at bedroom volume. It sounds and feels like it is being starved to death. In a room where I can open the 2-Channel up, there is absolutely no comparison. However, I stand by my assertion that bedroom and spouse-approved volume levels and tube technology are basically mutually exclusive. It is a compromise situation. The Archon suffers from the same problem when run at bedroom volume. Even if we generate a lot of distortion in the preamp, the phase inverter (PI) and the power tubes are part of tube amp tone and feel. Some of this magic can be maintained by using a post-PI master volume, but back EMF does not come into serious play until the amp is opened up.

    We can use an attenuator, but good attenuator design is a black art because impedance is not a synonym for resistance. Resistance is a measure of resistance to the flow of direct current. Impedance is the resistance to the flow of alternating current, and alternating currents have frequencies (e.g., the power at a U.S. power receptacle has a frequency of 60Hz). A guitar signal is an alternating current that is induced in pickup coils when the ferrous strings cut magnetic lines of force in a magnetic field. Anyone who has taken an ohm meter to an 8-ohm speaker knows that it does not read 8 ohms. That is because speakers are rated at nominal impedances, and impedance is frequency dependent due to impedance equaling the SQRT(R^2 + X^2), where SQRT equals the square root function, R = resistance, X = reactance, and the symbol "^" meaning raised to the power of. Reactance (X) is the difference between inductive reactance (Xl) and capacitive reactance (Xc). Inductive reactance is 2 * Pi * f * L, where Pi = 3.14, f = frequency in hertz, and L = inductance in henries. Capacitive reactance is 1 / ( 2 * Pi * f * C), where Pi = 3.14, f = frequency in hertz, and C = capacitance in farads. Speakers are both inductive and capactive. As output power is the square of the output transformer secondary voltage divided by impedance, the power delivered by the amp to the load changes with respect to frequency because speaker impedance changes with respect to frequency due to speakers being inductive devices. Tube amp power is rated by measuring output transformer secondary voltage into an 8-ohm dummy load, which is a non-inductive resistor bank; therefore, its resistance to the flow of alternating current is not frequency dependent like a speaker. Add in the fact that a speaker is a magnetic transducer that can also produce electrical current when the voice coil moves through the magnetic field that flows back through the power transformer into the power tubes (a.k.a. back EMF), and we have a very difficult real-world design problem on our hands.
     
    #493 Em7, Jun 14, 2018
    Last edited: Jun 15, 2018
  14. Dirty_Boogie

    Dirty_Boogie Still got the ol' tagger on it

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    Well that clears things up! o_O

    Seriously though, nice explanation. Almost 30 years since I graduated with my EE degree, and this brought back good memories (mixed in with night sweats before finals.)
     
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  15. elvis

    elvis Hamfisted String Banger

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    I find that neither my tube amps or my axe fx sound or feel great at bedroom volume. But they get the job done.

    And I play loud whenever I can.
     
  16. LSchefman

    LSchefman Hears Tones

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    1965

    “Turn down that noise!!”

    “But Mom, it sounds best when it’s loud!”

    1970

    “Turn down that noise!!”

    “WTF, man! Never trust anyone over 30!”

    1979

    “Turn down that noise!!”

    “If it’s too loud, you’re too old!”

    1988

    “Turn down that noise, the baby’s sleeping!!”

    “Aw, grumble...”

    2000

    “Turn down that noise!!”

    “But. My. TONE!”

    2018

    “Turn down that noise!!”

    “Never trust anyone over...uh....If it’s too loud you’re...umm...”
     
  17. DreamTheaterRules

    DreamTheaterRules New and improved member

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    Yes, feel (amp wise) is gone at low volume, with either. Find a tone that’s decent and work on riffs and songs. But whenever you can move some air, enjoy real tone!
     
  18. DreamTheaterRules

    DreamTheaterRules New and improved member

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    And there you have it! Decades of knowledge in one post.
     
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  19. DreamTheaterRules

    DreamTheaterRules New and improved member

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    So, what I’m saying is, I read all that, studied all that, built and modded pedals and amps for years, and finally decided to stop wasting time with all that. For me, it was a tough decision, because I kept thinking I could build or design a better mousetrap. What I finally decided is that, I have a job, a wife, a family, and a life of other things. What time I do have for music, is FOR ME spent much more productively, more ENJOYABLY, when I’m playing guitar, than when I’m studying design theory, modifying or building pedals or amps, or reading amp or pedal forums. I can buy a great amp and a few great pedals and actually enjoy “playing” rather than spending all my time trying to build, mod, tone critique...

    I’ve still got 3 or 4 un-built pedal kits in the music room. TONS of caps and resistors and all kinds of other stuff I need to get rid of. I’ve actually shaken hands with the devil and would rather PLAY through my Mustang Mini for 45 minutes than spend 45 minutes modifying pedals or amps or reading about either in the forums.

    Giving my brain a rest and letting my hands and ears have some fun. :)
     
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  20. bluenova

    bluenova Electrified since '84

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    Maybe I’ve missed it somewhere but what’s you’re history with building amps? This tech talk is awesome!!
     

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