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Thread: M/B innovations like SimulClass and DynaWatt: Are they any good?

  1. #1
    Member Joe Bee's Avatar
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    M/B innovations like SimulClass and DynaWatt: Are they any good?

    Hi there,
    I was recently browsing through Mesa Boogie patents to gather some ideas and I was wondering what you guys thing about Randall Smith's inventions. Is it just marketing garbage, or do the inventions actually make a significant audible difference?

    Take for example DynaWatt, patent 4,713,624 which you can serarch here
    http://patft.uspto.gov/netahtml/PTO/srchnum.htm
    It seems to be quite a clever circuit with the screen supply decoupled from the plates with a big capacitor, which is charged through a rather large resistor to give a long RC time constant. I guess the effect is that you get a lot of clean headroom when you play single notes, but once you hit it hard, you get a sagging compression effect.

    The most classic is probably the SimulClass patent 4,532,476 which I found to work by running a pair of output tubes not only in class A, but also conntected as triodes. Allegedly this makes the whole amp sound like triode class A, although I don't know whether this is a good thing in a guitar amplifier.

    The Duo-Class with switchable Push-Pull / Single-Ended power is rather new and probably interesting for those who feel the need to drive a 5W power amp into deep saturation (power-scaling anyone?).


    Anyway, I do not own any Boogie amps and I have never played around with one long enough to really pay attention to these things.
    I am pretty sure that if any of the above techniques had a real influence on sound it would have been copied by countless other manufacturers, just like the 39k cold bias stage from the SLO-100 can be found in each and every high gain amp today.
    On the other hand, why would Boogie do it if it had no point, considering they are trying to sell products to innovation-hostile guitarists.

  2. #2
    Noodle of Reality Steve Conner's Avatar
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    Randall Smith once tried to patent the half-power switch, which I believe was originally described in a RCA applications book in the 50s. I think most of his "innovations" are no more patentable than that.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  3. #3
    Member Joe Bee's Avatar
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    I gather you don't like the business practice of patenting everything from "software dialogue boxes" to "round things intended to make moving stuff easier" very much, but I guess so does everyone with a bit of common sense. So let's forget for a moment that he actually patented these things, and just pretend a fellow diy enthusiast came up with them. (I suppose this has happened countless times anyway, long before Randall ever though of them.)
    From this point of view, are any of the circuit ideas worth dublicating? Even if the ideas are quite simple it could take some time to get it right, so before I try it I would like to know what other people think about this stuff.

  4. #4
    Senior Member Enzo's Avatar
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    Patent/schmatent, I think the point is that these are not really innovations.

    Wiring pentodes as triodes is nothing new. Running screens from separate supplies or substantially decoupled from a common supply is nothing new. What was I looking at the other day - Music Man maybe? - had the plates on 700v and the screens on 350v.

    It is all a matter of knowing WHY each part is in an amp and what that part does. THEN you can tweak its value and maybe alter the relationship to everything else. (For example adding a diode between the plate supply and the rest to prevent sag from getting into the preamp.)

    Even some simple things might take time to get right indeed. But that is not limited to these "novel" ideas. If you design an amp from scratch, to get it where you want it, you will be tweaking the values of the plate loads, the cathode resistors, the bypass caps, the interstage coupling caps, etc. AFter all, the circuit itself from a Fender and a Marshall are pretty darn similar if you leave out the values.

    Sure these things are worth a try, just as it is worth trying different cathode bypass arrangements, different B+ voltages, different tone stack values, different tone stack styles, and so on.

  5. #5
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    I have a Boogie with Simulclass output. With the switch in the supposed class A mode, the two tubes are not biased any place near class A. My EL34's are at only around
    30 ma each But still they sound very nice with the screens tied to the plates in this circuit. What gives the Simulclass amps their unique sound IMO are the EL34's and 6L6's running in parallel, or the EL34's also sound very nice by themselves. My guess is that the EL34's are putting out way more in class AB, than the claimed 18 watts class A, or whatever those ads said. Would be fun to measure sometime.

    But I think we need to give Randall some credit. I think he is a very good marketing/amp designer person. I think he's made a few bucks on his inovations over the years. Wonder if he ever has time to read these forums

    Kevin

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    Having played the Mesa Boogie Lonestar models I ca say that they do sound very nice. In fact I am in the process of building a simplified version of this amp with a parallel push pull output stage using 6L6GC's. Look at my thread
    designing a 15W/30W power switching amp

    The power amp schematic is basically the same as that of the Lonestar; so how does the switch between ground and the second pair of 6L6GC's work? And for those famaliar with the lonestar model how does Randall Smith do low power single ended and high power push pull class AB in the same amp using one OPT??

  7. #7
    Senior Member Old Tele man's Avatar
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    ...just "new" paint on "old" ideas.
    ...and the Devil said: "...yes, but it's a DRY heat!"

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