Power Scaling methods, how do these work?

Discussion in 'Amps and Cabs' started by yannis, Jul 13, 2006.

  1. yannis

    yannis Member

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    Hi all,

    I have been reading around recently (Reeves, LondonAmps, MavenPeal etc..) with respect to power scaling. I have visited the relevant sites (londonpower and MP) read all the material etc.

    Since i am not insanely proficient with circuitry yet (but i do understand some fundamentals), i wonder the following.

    Using a power scaling method, you can overdrive the power-tubes by using less voltage to them. Thus you get the familiar/desireable tone at lower volumes. The tubes last longer, the amp runs cooler. This can be achieved with either a extra variable transformer or valve or something.

    My questions.
    1.How do you overdrive the powersection using less voltage?
    2.Is it in general reliable? Does it mess up the signal path? (i have the option to be bypassable).
    3.Is it as effective (or more effective) than a Hotplate, valve switching, triode/pentode solutions?

    I know that the RG88 that i heard online (thanks dbx) was AWESOME at talking levels.

    Thank you for your replies.
     
  2. trisonic

    trisonic Member

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    The Maven Peal system and the Power Scaling system do not work in the same way.

    Only the designers/engineers can decide how much information they can impart on a public forum.
    I should add that I have a Ganesha. The "Wattage" and "Sag" work very well indeed - they impart the quality of a cranked amp at lower than ear shattering volumes. Dave Zimmerman never intended his system to work at so-called "Bedroom Volumes" however. They work well on small stages/studio situations.
    Other members have had great success with "Power Scaling" but I cannot comment never having tried it myself.

    Best, Pete.
     
  3. yannis

    yannis Member

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    Cheers trisonic,

    I do not want proprietary details for the associated designs. I just need to know, if as a solution it is a sound solution for appartment living versus a hotplate or triode/pentode/valve switching stuff. Furthermore i would like to know if there are any reliability issues in having an amp with power scaling versus an amp without one (i am not talking about DIY powerscaling add ons).
     
  4. fullerplast

    fullerplast Senior Member

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    Yes, absolutely. IMHO it sounds better and is more versatile than an attenuator or valve switching schemes. Nothing is in the signal path at all and it is continuously variable. There may be some amps that sound better with an attenuator, it can come down to personal preference.

    An amp with power scaling is generally going to be running cooler and will stress the OT and tubes less than running an attenuator. That being the case, it should result in better reliability and longer component life.
     
  5. yannis

    yannis Member

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    Good to know, i ll be having then a valve driven varipower ;) i ll keep you posted soon! Is the concept basically to reduce voltage going to the main power tubes?
     
  6. PB Wilson

    PB Wilson Member

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    Pentode/Triode switches really don't do much to decrease the overall volume. It would probably be the last choice for acceptable bedroom/apartment jamming.

    Translation: My wife can't hear the difference when she's telling me to knock it off and put the guitar away when she's trying to sleep. :nono
     
  7. 908SSP

    908SSP Supporting Member

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    As much as I love the Maven Peal I think fundamentally they do work the same at the level of the power tube itself. There is only so much that can be done in the tube to make it over drive at lower levels, tubes are relatively simple things.

    Blankenship has added another option to that list and his too works on the same basic principle.

    Now having said that there are huge differences in how you control the voltages going to the power tubes. The Maven Peal has by far the most sophisticated system regulating all the voltages keeping everything in balance automatically so with one knob the sound level goes down with no change in tone. From reading the PSK literature some manual adjustments need to be made to maintain the tone. On the Blankenship amp he puts a Variac in the circuit to control the voltages to the power tubes while maintaining the heat voltage separately.

    I am not tech a so my understanding is very basic. Read an article on the inner workings of a tube you will be surprised on how simple a device it really is.

    All of these systems work like I said I think the Maven Peal is the top of the heap but it is limited to factory builds. The London Power is an invasive kit so it is possible to install in your clone but not something I would choose to do to a old amp.
     
  8. fullerplast

    fullerplast Senior Member

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    Generally yes. There are various schemes however and it can be extended to other sections as well.
     
  9. µ¿ z3®ø™

    µ¿ z3®ø™ Member

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    waiting for my JMJ w/ power scaling to experience it for the first time.
    like almost everything in life there are always tradeoffs.
    w/ powerscaling one is not gonna get the output tranny saturation effect that some amps achieve. now it's absolutely true that this does stress the components, but there's only one way to make that happen.
    but i am looking forward to checking it out on the JMJ.
    i've also been looking at the update to kevin's website and the new studio amp and the immense amount of control there is over certain sections of the amp. whilst i generally shy away from amps w/ loads of knobs, it's usually because they are switching amps w/ a plethora of volume and tone knobs. i like the idea of being able to control other aspects of an amp.
    but danged if that amp ain't a truck load of $$$$$.
     
  10. yannis

    yannis Member

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    I understand that you cannot bypass the laws of physics... aka speaker distortion, air movement and transformers saturation. I am only wondering if the power scaling on the screen plate voltage (cathode bias) is a very good solution to tame volumes for appartment living versus using attenuators.
     
  11. Wayne

    Wayne Member

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    Would you mind posting a link to this? I'm not sure which site you are referring to. Thanks.

    Wayne
     
  12. MikeT

    MikeT Member

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    Kevins page is at http://www.londonpower.com
    He currently has a session amp (I think this is an older design of his) for $1000...

    must resist...

    Mike
     
  13. Wayne

    Wayne Member

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    Thanks. Looking forward to seeing the amplifier line.

    Wayne
     
  14. 56_Special

    56_Special Member

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    I'm having a London Power powerscaling box installed in my 18 watt Marshall clone as we speak. Believe it or not, this amp (with 2X12's) is too loud for rehearsal with my band. (They are always telling me to turn down and get a dirtier tone. I tell them its one or the other. They roll their eyes. *sigh*) At gig's, it's the perfect stage volume. Anyway, when it's installed, I'll tell you how it works out. I'm guardedly optimistic.

    Martin
     
  15. µ¿ z3®ø™

    µ¿ z3®ø™ Member

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    altho' i'm looking forward to experiencing the powerscaling phenom w/my JMJ, i would think that for an apartment, it would be far preferable to not strain the output tranny and tubes. peeps who have used powerscaling seem to love it. with any amount of massive attenuation there will be a significant change in tone, partly because of the fletcher/munson curve, partly because of the psychoacoustics involved and partly because of the lack of speaker distortion.

    18 watts is LOUD. in the past few years i've only rehearsed w/ one drummer that was so loud that no attenuation was needed on a tweed deluxe. stage volumes can vary w/ the venue, as U say.
     
  16. tonefreak

    tonefreak Member

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    From John Suhr regarding the Badger and Power Scaling:

     
  17. tonefreak

    tonefreak Member

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    More from Suhr:

     
  18. µ¿ z3®ø™

    µ¿ z3®ø™ Member

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    hence the reason, i presume, why some attenuators sound better w/ certain amps/cabs than others.
     
  19. muddy

    muddy Member

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  20. reeves amps

    reeves amps Member

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    Agreed...that's why we Power Scaled our most recent offerings.
     

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