Supro Thunderbolt loudness issue

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Knucklehead, Feb 28, 2006.


  1. Knucklehead

    Knucklehead Member

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    I've got a '64 Supro Thunderbolt, it's the model with a 15" Jensen, 2 6L6s and a tube rectifier. I haven't played it in a long time and powered it up today. Seems like it's not as loud as I recall, in fact my '55 5E3 Tweed Deluxe sounds significantly louder. I put some fresh 6L6 tubes in the Supro, but it's still not any louder. It does have a great vintage crunch to it though. I alays thought 6L6s were more powerful output-wise than 6V6s.
    Any thoughts on the loudness issue, could it be another tube or part?
    Thanks!!
     
  2. Reeek

    Reeek Member

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    I'd be swapping out the rectifier next
     
  3. 59 Deluxe

    59 Deluxe Member

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    i actually used to have the same model supro, while having a deluxe as well. the supro sounded great (when it was cranked) but i would agree that my deluxe appeared louder.

    i would have to leave it to other experts as to why this would be. transformers in the circuit maybe?
     
  4. Dave Orban

    Dave Orban Gold Supporting Member

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    Mine was not particularly loud, as I recall... REALLY nice breakup, but definitely not a lot of headroom or volume...

    You could try a higher-efficiency speaker, and that would give you a bit more, but the trannies weren't all that large, from what I can recall...

    In spite of that, I do wish I still had mine...!
     
  5. Knucklehead

    Knucklehead Member

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    Thanks for the comments, I'll try the rectifier tube swap tomorrow. Does anyone know the RMS wattage rating for the Supro Thunderbolt and a 5E3 Deluxe, both are stock without any modifications?
     
  6. donnyjaguar

    donnyjaguar Member

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    I'd be suspicious of the power supply capacitors myself. They could be pulling down the HT due to internal resistance.
     
  7. Knucklehead

    Knucklehead Member

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    "I'd be suspicious of the power supply capacitors myself. They could be pulling down the HT due to internal resistance"

    This is a good point, I remember the Supro being easily twice as loud as it is now. I'll check thes power supply caps.
     
  8. jamielee

    jamielee Member

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    hello, just wondering if you figured out the problem. i also have a thunderbolt and it has a non original transformer in it. i read about how loud these amps are, but mine is not that loud. i am wondering if it is the transformer or something else. thanks

    just figured out the issue with mine. this explains the loss in low end and volume. the coil is frozen, so the speaker is not moving and pushing air.

    Voice coil burnout or rubbing. This is what is typically meant when we say a speaker is “blown.” A “blown” speaker commonly exhibits no external indications of damage, because the voice coil is not visible without disassembly, but this is by far the most common sort of speaker malfunction. It results from a buildup of heat in the voice coil, from excessive amplifier power or “clipping” distortion, which overcomes the ability of the speaker design to dissipate. When the overheating is sufficient, the relatively thin wire in the voice coil can actually melt at some point and develop an open circuit; when this happens the speaker stops making sound of any sort, and an ohmmeter placed across the speaker terminals will indicate no resistance whatsoever, because of the open circuit. Or the voice coil can deform from the cylindrical shape it must have to move back and forth in the magnetic gap. The speaker may still make sound, but it will be distorted, and when you push the cone in and out by hand there will be a “scraping” noise, felt as much as heard, which indicates that the voice coil is rubbing in the magnet gap. Other physical indications of a “blown” speaker can be an inability to move the cone in and out manually, indicating that the voice coil is stuck in the gap (from overheating, deformation, maybe even melting of the insulation or adhesives used to assemble it). I have seen speakers where a combination of voice coil damage and overexcursion has resulted in a cone which can be pushed in and will stay there, can be pushed out and will stay there, but will not “center” to its normal resting position.
     
    Last edited: Dec 8, 2008

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