Attenuator question ( need help)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Mooncusser, Jul 7, 2006.


  1. Mooncusser

    Mooncusser Member

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    Hi everyone,

    I need to ask a question.
    I have never used an attenuator before.
    I have a few questions.
    If I buy a Weber MASS 100 for my Marshall 1959 SLP, how much tone will it suck?
    Does it sound artificial or feel processed, and just how much can you crank the amp and be able to enjoy the yeilded output in say, your basement? ....without buzzing the neighbors. (kinda hard to explain that last one, but I think you might see what I'm getting at.)
    Anyway, Thank you very much for your advice and opinons.
    Take care and best regards,
    Mass
    __________________
     
  2. John Phillips

    John Phillips Member

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    First and very important, you need a bigger attenuator. The Mass 100 isn't enough for a 100W Marshall, you need at least the 150W model (Weber will tell you this too). A cranked amp puts out far more than the rated power - Marshall Super Leads among the most, many are well over 150W and some over 200W fully-distorted output.

    (This is something that really annoys me, not just about Weber - IMO an attenuator should be rated for the amp power, not the actual electrical power. A '100W' attenuator should be capable of taking the full output of any '100W' amp on the market IMO, exactly to avoid confusion like this. If it isn't, and blows, you can count on expensive amp damage up to and including a blown OT.)


    Second, I don't think any attenuator will give you quite what you're looking for at practice levels from that amp. IMO they don't affect the tone as badly as some people say they do, but when you get beyond about -10dB all bets are off really - and at -10dB the amp is still putting out 10W, which is LOUD through a normal speaker cabinet... much louder than what I would think of as home-practice volume, but that depends on your home :).

    IMO they also affect the tone worse on cranked non-MV amps using power-stage distortion than they do on MV amps or cleaner amps with pedals in front, for the same amount of attenuation and/or final output volume. I've got much better tones at lower volumes using a combination of pedals and/or MV as well as an attenuator, than with just an attenuator alone. I know that's counter to popular belief about 'power stage distortion being best', but it's what I hear. I actually find I can use up to at least -20dB of attenuation and have it still sound good when the power stage is not overdriving.

    So as well as the attenuator, I would look into getting a good overdrive pedal (if you don't have one already) and possibly having the amp modded with a post-phase-inverter MV, which are usually better-sounding than preamp masters if you're looking for a lower-gain, pushed-power-stage tone. Then the idea is to get the amp up to just enough volume to start to sound good, while using the minimum amount of attenuation. You should be able to find a 'sweet spot' that way.


    Hope that helps! :)
     
  3. Wakarusa

    Wakarusa Member

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    A second thing to consider is the reliability of the SLP. Running dimed into an attenuator is the same as running dimed without (from the amp's point of view). This stresses the heck out of the output transformer and, particularly in the case of the more recent Marshall amps, will quickly destroy the OT from heat. The numbers behind John's claims are sound - at full clip you're closer to a square wave output than a sine wave and a square wave represents around twice the power of a sine wave with the same amplitude. Your OT (and any replacement OT I'm aware of) won't like the heat from 200W+.

    For my customers that insist on using attenuators on 100W Marshalls I set 'em up with two of the output tubes removed (and a nice drawing of how to connect everything up to get the recommended impedence matching). The tone is pretty close and the output power is now limited to something the OT can withstand.
     
  4. Mooncusser

    Mooncusser Member

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    You both took quite some time being more than thorough.
    I have saved this post onto a word doc., as it is so informative.
    I want to thank both of you for your time and efforts, it really helped me out ALOT!
    Best regards to you as always,
    Mass
     
  5. van_wylde

    van_wylde Member

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    Hi there,

    i have found the THD range of attenuators to be slightly better than the weber ones. However the problem is you have to select the righ Ohms with the THD and if you ever decide to change your setting it means a new attenuator.

    i want to second what wakarusa said about if you are to use an attenuator on a 100watt amp you should take out two of the power tubes.

    I have also found that when using a attenuator it is better to use smaller speakers. For instance if you are using 12 inch speakers i would consider buying a 10 inch speaker. it just seems that when you push a speaker harder you get a lot better sound and by using a attenuator you are not really pushing bigger speakers all that hard, hence i find it better to use a smaller speaker.
     
  6. Jon

    Jon Member

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    Hope this doesn't sound too negative, but it's a bit like asking whether you can limit the speed on your Ferrari as it's a bit fast for popping down to the shops - on a large amp I would say that attenuators are very useful for dropping the output by a certain amount to tailor your amp to a particular size of venue (I use a Weber Mass with a Victoria Sovereign - works great as the unattenuated amp is just a bit too much for smaller venues), but for home practice you really would be better off getting a dedicated amp - there are loads of low wattage amps aimed at home recording/very small gigs so it might be more tonally satisfying in the long run to look at one of these. THD univalve might be a good bet, or Cornford Carrera, or MiniZ?
     
  7. Rich M

    Rich M Member

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    I agree with the "pull two tubes" and use the 100W Weber. Although I've gone further and added a PPIMV (hole already there) and cut B+ in half (with rebias) to get the power levels down to basement levels (~12W). I have a Weber MASS but rarely use it, except when bench testing, as I can pretty much get any sound without it that I could with it (actually, the clean headroom is reduced a fair bit, but I am a gain freak). And the RCA branded Mullard XF2s that are in there can breath a bit easier.
     
  8. Wakarusa

    Wakarusa Member

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    The suggestion to pull a pair of tubes is for reliability/durability, not tone. In fact, the tone from a pushed pair is subjectively not as rich as the tone from a pushed quad - but still pretty good. It's a compromise to try to get you the power tube distortion you want without blowing the OT. I'd argue this is more important in a current production Marshall than your VHT -- Stevie uses better iron than Marshall's accountants will allow.
     
  9. Wakarusa

    Wakarusa Member

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    I'm wondering if you have the impedance settings correct for the 1959HW setup.
     
  10. Mooncusser

    Mooncusser Member

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    The HW is a bit out of my price range, (my dream amp) but I was able to aquire a 1959 SLP RI W/ no effects loop.
    I agree with Lashing. I am never going to need the 100 watts. I have just ALWAYS wanted this amp, and even though it is to much, it is staying for now. I just adore the dynamics this amp gives, even at low volumes, but it isn't going to see a stadium.
    But man, I am SURE looking forward to opening this thing up someday!
    :drool
    Peace,
    Mass
     
  11. danieldroukas

    danieldroukas Member

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    Rich M ... what was your method for halving the B+
     
  12. Jammin'John

    Jammin'John Member

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    A 100w amp is too much amp for most gigs!
    In the basement.........holy c%^p
    A great attenuator,like a THD,is $300.
    Why not just get a dedicated head or combo of less power & run it through your cab ?
    When I use an attenuator in a live setting I rarely use more than - 4db.
    Any more than that and the speakers aren't movin' enough air !

    JJ
     
  13. EXP

    EXP Supporting Member

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    +1 on the PPIMV. an attenuator will run you around $200+ , whereas the master vol mod runs around $50. i would go with the PPIMV.

    the half-power switch '' two tubes pulled '' is a great idea too. puts less strain on the transformers and tubes.
     
  14. EXP

    EXP Supporting Member

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    also when you add a PPIMV(being that its a 1959SLP). correct me if im wrong Marshall owners, but if you dime the Master Vol, it puts it back to specs of the original circuit.
     
  15. EricPeterson

    EricPeterson Member

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    I would spend the 300 dollars on a small tube head. I have pushed it before but i think it is a good alternative, try the epi valve junior head it is 99 dollars and has tons of mods that can be done to it all of which will still bring it in under the 300 dollar price tag of some of these attenuators
     

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