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New Mesa All Tube Amps - Strategy and Prodigy (fresh start v 2.0)

Discussion in 'Amps and Cabs [BG]' started by Chris Fitzgerald, Jun 20, 2013.

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  1. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
  2. Lex P.

    Lex P. You've got it awful loud -Kathy P. Supporting Member

    Mar 19, 2003
    Two NV115's just waiting and waiting and waiting for the Prodigy. Actually I just got them yesterday but it seems like I've been waiting and waiting and waiting........

    I work in new product development and no all to well how long it can take to get things right and out the door. From what I've heard so far it sounds like it will be worth the wait!

  3. MesaBoogie


    May 14, 2013
    Petaluma, California
    Customer Service/Product Specialist: Mesa Boogie
    Hey everyone! Our fearless leader Randall Smith has had a chance to read through most of the thread following our GTG, and wanted to shed some light on some of the more technical aspects of the discussion. We'll start of with an in-depth reply to StuartV's thorough post from the last thread, http://www.talkbass.com/forum/f15/n...-fresh-start-885496/index50.html#post14421833, which goes into some fairly heavy detail. Ladies and Gentleman - Here's Randy!:

    Go to the head of the class, Stu: You were really paying attention to some of the technicals I spewed during our factory tour. Most everything you wrote is technically correct though I'd like to add a little more info. Quickly...As for 'per tube' watts, the Strategy is rated at 465 watts and the Prodigy 250 watts (@600Hz). Not far from what you mentioned but just trying to be accurate. OK...

    1. Power ratings and transformers: The SVT is an icon which we all respect highly. What we're trying to do is somewhat different, since SVTs are well known and available. Biggest complaint is weight and size. Our approach is to use more tubes (8 vs. 6) with a higher plate voltage rating (KT-88 @ 800 vs. 6550 @ 600). (And the Prodigy is for those with more typical requirements.)

    2. Instantaneous power in joules is a function of voltage SQUARED times current. (You can see where this is going and it's why tube amplifiers of lower continuous power rating may sound far more powerful than higher rated transistor amps, since their operating voltages are usually under 200.) 700 squared is an enormous number!

    3. To minimize weight, our transformers use grain-oriented, silicon steel for their laminations which have a greater magnetic capability than lesser grade iron. And to maximize available current, we use ten jumbo filter capacitors whose primary job is not filtering but storing electrons.

    4. Music is highly dynamic and the attack of a note requires vastly more horsepower than whatever comes immediately thereafter. Picture the flash-bulb analogy: it's not really so much light, it just occurs all at once. Our amps operate far more in this fashion than does the SVT.

    5. Nevertheless, our continuous power ratings, AFTER the initial attack burst, are still impressive: More than 450 for the Strat, more than 250 for the Prodigy. And the recovery time for the caps to fully re-charge is a function of the AC line (i.e. at 60 Hz, it takes 1/60 of a second to recharge. ( I admit it takes longer in Europe, 'cuz they operate at 50 Hz.)

    6. Now, for the strain on the tubes: everything you say is correct but overlooks a most critical factor: Plate Dissipation. This is the wasted heat generated by inefficiency in the tube's ability to conduct electrons. In a pure Class A amplifier, that waste product is 50%. In a Class C radio transmitter, that wasted inefficiency is close to zero. In both our Strat and Prod it's very low, way less than half the tube's rating. Yet this is the bias and operating condition we arrived at BY LISTENING for the sweet spot, not dialing for specs.

    7. After determining these voltages primarily by their musicality, I was particularly thrilled to see-- and hear-- that biasing them to run hotter (less efficiently) tended to sound dull and less alive, though there is no doubt at all that their distortion specs would have been improving. We follow the same practice with guitar amps and generally find the same results. Years ago when we dabbled in high-end stereo (Mesa Baron and Tigris) it was distressing to see how the specs improved, never mind the sonics, as the "waste factor" was increased.

    8. An apt analogy to this biasing thing is a clutch, if y'all remember when cars had that third pedal. When the clutch is slipping, it's wasting a bunch of power, turning it into waste heat. When it's locked up, it can transfer enormous power with no loss. Pure Class A amplifies like a clutch that's slipping 50% of the power. The way amplification is achieved is by modulating that slippage: No signal = 50% slippage. Half power = slippage varying from 25% to 75%. Full power = varying from full lock up (fully conducting) to fully slipping (zero conducting). BTW... saturation distortion (clipping!) occurs when the incoming drive signal is telling the power amplifier to swing BEYOND fully off and fully on... which of course it can't do. Thus the flattened top and bottom of the clipped wave form represent the limits of the power amplifier beyond which it cannot go.

    8. Got that? Good. So... what the power amp does, is conduct the resources of the power supply to the speaker in accordance with the incoming signal. We have a huge storage capacity sitting at a nice high voltage, ready to be unleashed by a phalanx of big valves. And whereas Hi-Fi specs are static, music is dynamic. So our approach from the first has been to serve the artist in his musical quest and the specs be damned. (In fact that was our problem in the hi-fi realm: The reviewer who LISTENED to the Tigris, had multiple aural orgasms. The technical reviewer noted that the specs sucked-- "This amp is more like a musical instrument" was his conclusion. And a greater compliment he couldn't have provided, no matter how inadvertent!

    9. With the venerable SVT in mind, our goal with the Strat was: "Half the weight, half the size, 50% MORE powerful, and tons of TONE". There will always be a welcome spot on the landscape for the great old SVT. Longevity is one of the best qualities of musical instruments and the SVT has truly earned its place in the pantheon of classics. Your SVT is "just right" for you-- keep it. We'd far rather have our friends happy with another's amplifier than unhappy with ours.

    10. Just don't ask me to carry it!

    Mvilmany, oaklandthumb and zenrad like this.
  4. MesaBoogie


    May 14, 2013
    Petaluma, California
    Customer Service/Product Specialist: Mesa Boogie
    One other historical tidbit Forum readers may enjoy:

    The first of the SVTs used 6146 power tubes, a wonderful device rated at 900 volts (with a plate cap!) which I used as a kid to build transmitters. When Ampeg switched to 6550s, they said it was to "take advantage of that tube's greater plate dissipation" thus illustrating what I'm talking about regarding operating efficiency. Unfortunately, the plate voltage was considerably higher than 6550s could reliably withstand and I recall unhappily, many of them arcing out immediately. This was back in the Prune Music daze and I recall one poor guy ready to punch me out 'cuz his SVT blew up at an important gig... shortly after I had re-tubed it. Needless to say, I was extremely bummed... it was then that I showed him that the tubes were getting 100 volts MORE than the published GE maximum! Quieted him down somewhat. Anybody still have a original 6146 SVT? How do they compare to the 6550 ones? I presume Ampeg lowered the plate voltage and increased the idle current, the opposite of what we've done.

  5. husky123

    husky123 Supporting Member Commercial User

    Jul 6, 2006
    Leesburg, VA
    Product Development Specialist for Bergantino Audio Systems
    GAS attack!
  6. Dave W

    Dave W

    Mar 1, 2007
    White Plains
    How are we looking on release dates?
  7. Man, this just got a lot more geeky!:hyper:

    I wish the industry as a whole would use a more appropiate frequency (say 40Hz) when measuring for ratings. Maybe there is a reason, I don't know.
  8. Primakurtz

    Primakurtz Registered Nihilist Supporting Member

    Nov 23, 2011
    Denver, Colorado
    Thank you, Dr. Smith! This explains some of the "quickness" of my old D-180 as well, I assume.
  9. svtb15

    svtb15 Banned

    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig. Q+
    Regard #5 above.
    I will say . The one thing that i really dig about the Mesa amps is what i have said prior...
    After the initial attack, the Mesa seems to be able to hold onto the note and good way. And allow it to decay naturally.... Not many amps do that.. Maybe that is due to the power supply... .. And it does it up to pretty loud volumes... Very Musical sounding topography
  10. JGR

    JGR The "G" is for Gustav Supporting Member Commercial User

    Jun 29, 2006
    President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
    The SVT's run around 700 volts on the plates which sags closer to 600 under load, keeping the 6550's within their dissipation ratings (though on the edge!). The 6550 has a lower power sensitivity than the 6146 so it required a higher screen voltage, and I believe that was the biggest thing that was changed. The 6550 SVT's run around 400 on the screens; bumping the 22K screen resistors up does more for their reliability.

    Randall (great to see you here BTW), I'm still wondering about the power ratings and transformer weight... to achieve over 450 watts RMS, you need a 1000+ VA power tranny which would be in the 25-30 lb range, and an OT with decent low end response is gonna be in the mid to upper 20's too... as a point of reference, the Aguilar DB728 is 57 pounds using torroidal PT an OT's.

    Can you tell us what the RMS power is at say 80 and 40Hz running into a dummy load - typical power test scenario? Also, what screen voltage are these guys running?
  11. KwinS

    KwinS Supporting Member

    Oct 30, 2006
    Dallas/Ft. Worth
    I think I'm going to pick up a second Walkabout Scout 1x12 extension cabinet tomorrow. That way I'll be fully prepared for my Prodigy whenever it shows up.

    ...and now this thread will pop up under the "participated" tab.
  12. Session1969


    Dec 2, 2010
  13. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    Glad to have that additional info! Now I'm sort of interested... :bag:
  14. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
  15. godspeed68

    godspeed68 i'm here for the sound Supporting Member

    Mar 24, 2004
    Chicago, IL
    i'm incredibly psyched on trying these...but it glows blue?...
  16. speyer

    speyer Supporting Member

    It's gonna glow alright! I was at my buddy's place last night and he has a MesaTransatlantic. It looks like a mini prodigy only silver. Its not turned on in this pic... But it lights up the entire room with those blue LED's.

    Can you find it?

  17. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Dear Mesa Boogie,
    Thank you for such a clear post with very interesting technical information while eliminating the corporate BS that sometimes shows up here.
    I must admit that I sold my Walkabout ONLY due to lack of clean headroom.
    I will be looking forward to trying the Strategy.
  18. Jazzbass2010


    Dec 14, 2010
    Are there any more audio video clips of the prodigy ?
  19. speyer

    speyer Supporting Member


    More Prodigy clips please. :)
  20. godspeed68

    godspeed68 i'm here for the sound Supporting Member

    Mar 24, 2004
    Chicago, IL
    someone should start a dedicated prodigy/strategy clip thread.

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