Aluminum Chassis, what are your thoughts?

Discussion in 'Amps and Cabs' started by teleamp, Jun 24, 2008.

  1. teleamp

    teleamp Senior Member

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    I just buuilt a tweed deluxe using an aluminum chassis and I think there might be some sonic differences. How do you guys feel about chassis material?
     
  2. doctord02

    doctord02 Member

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    Since Aluminum is not ferromagnetic, sure it might make some differance... However, I'd bet that differance is about a hundred items down on the list of things that really are likely culprits, like speaker choice, wire choice, componet choice, lead dress, etc...
     
  3. Wizard of Ozz

    Wizard of Ozz Silver Supporting Member

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    I don't mind it, as long as it is reinforced to withstand the weight of both heavy power and output transformers bearing down on it during shipping. I've seen more than a few amps lately (especially aluminum chassis) that have been bent, squashed, deformed due to not being strong enough to properly support the weight of the transformers.
     
  4. teleamp

    teleamp Senior Member

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    I had the chassis custom made with extra reinforcement and I am using light weight iron.

    But I know exactly what you are talking about. Someone shipped me a high dollar 50 watt amp, the transformers acted like ballast in a dead blow hammer, wrecking the chassis, wiring, tubes and cabinet. Had the chassis fit the cabinet instead of being narrower and/or the chassis corners been welded....
     
  5. jdh

    jdh Supporting Member

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    Since the chassis is often used as the circuit common the conductivity of the metal will have an effect on the overall circuit response. Whether the corners are welded or not is another variable as well as the thickness of the metal. We all have our preferences and hierarchies in the design chain. I personally would say the chassis and its mechanical topology rates equal with wire type and size. Quantitatively I would rate the chassis as 1 of 10 variables that can make or break an amp. And yes, I prefer aluminum.
     
  6. guitarsnguns04

    guitarsnguns04 Member

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    I prefer aluminum as well....so did Ken Fischer :stir
     
  7. KarlH

    KarlH Supporting Member

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    Definite effect on tone, IMO

    steel = faster response, especially in the highs, more strident high end, easier to get that "explosive" response

    aluminum = softer highs, cushy lows, more forgiving with treble frequency detail
     
  8. quinnamps

    quinnamps Member

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    Examples of aluminium chassis amps are plexis, trainwreck, and dumbles.
    It is a better conductor than steel. many people feel aluminium has a faster response and better high end.
    It is non ferrous so it has less of a chance of hum issues. Also it will never become magnetic.
    Chassis' are almost always used as ground. Electrons can be argued to flow to ground or from ground but either way it would seem that ground plays a very important role.
    I prefer it from a technical point of view having reviewed lots of opinions and facts on the matter. I cannot say I have built an amp in one and swapped to another but my experiences and my senses of what i am trying to achieve have led me to it and I am sticking with it. Some may cite some technical problems with it using it as ground but practical experience has told this is not nearly as much of an issue in the real world as it is in theory. Plenty of really great, very infamous amps well over 30+ years without any more or less grounding issues than any of their steel counterparts.
    It does require you to not use the thinnest piece you can find which many have made the mistake of. Proper thickness will allow you to use all the same size controls, add a faceplate and provide a very strong mounting surface for transformers. Done right and no worries.
    Good stuff imo.
     
  9. teleamp

    teleamp Senior Member

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    I have been using steel, but the 5E3 that I built with the aluminun chassis is the quietest one that I have built. It is also one of the better sounding ones as well. I'm going to try aluminum with a couple of my amps and see how they turn out.

    I worked on an original 59 Deluxe a while back and notice that the PT was physically smaller than the ones being used in clones, so I used a Champ/V Champ/Bronco/Princeton/Deluxe replacement transformer which is the same size as the originals.
     
  10. stratman_el84

    stratman_el84 Member

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    One of the keys to successfully using aluminum chassis is choosing the correct alloy and thickness. Different alloys have different hardnesses as well as different conductivity characteristics. There are also things one can do to enhance the conductivity/ground quality of an aluminum chassis.

    The chassis I use to build the Testament MK-I 20 watt heads like mine linked to in my sig below are 10"W x 6"D x 2-5/8"H 6061-T6 1/8th-inch aluminum alloy, all pieces (top, front, back, sides) cut and welded, not bent. After cutting, welding, and holes are added, the chassis is sent out to be sand-blasted then chromate-conversion coated per MIL-C-5541F Class 3.

    The chromate-conversion coating protects against corrosion and also enhances the chassis' conductivity greatly (+30%-40%) making it an extremely-good conductor and reducing hum-and-noise-inducing ground-loop currents to negligible levels.

    The amp is extremely quiet and stable. Lows are extremely punchy and dynamic for a cathode-biased P-P 2/EL84 amp, rivaling fixed-bias AB2 designs, and the highs are glassy and smooth. The amp is amazingly dynamic and harmonic-rich.

    At the given dimensions, 1/8th-inch 6061-T6 is extremely rugged, especially as everything is welded and there are no bend-points to deform under weight/stress.

    Cheers!

    Strat
     
    Last edited: Jun 26, 2008

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