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Output Transformer/Reverb Upgrade for Sears Silvertone 1484

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  • #16
    For at least 20 years I've been telling people that the Twin Twelve really isn't amenable to mods that attempt to increase it's power output. It's designed to be a low power amp, and a large part of the circuit's characteristic tone comes from the low power operating point of the tubes coupled an undersized output transformer. The OT was so small that when people would try to hot-rod the amps the OT would invariably blow up. For the longest time a suitable replacement OT could not be obtained, so people would put in a Fender OT and the result would be that the character of the amp was markedly changed; the amp no longer had that thick, rich, creamy milkshake type of distortion. For this entire time I've been sort of a lone voice in the wilderness, crying out against the indiscriminate modding of some of the last true inexpensive PTP amps.

    Of course, nobody paid attention because SF Fenders could also be had for next to nothing and those were highly favored as modding platforms. The result was that the Silvertones received no respect whatsoever.

    Eventually the value of SF Fenders began to rise. Later on Jack White came along, and drove the prices of the "worthless" Silvertone amps higher and higher.

    What amazes me about these Silvertone amps is that even though people like them, but they never seem to be willing to accept them for what they are -- they always feel a need to mod them to get more power. Like Juan said, if a Fender is what you want then buy a Fender. If you want the characteristic silvertone sound, restore your silvertone, but don't hot-rod it. Hot-rodding these amps invariably causes critical parts to fail that destroys the amp, and replacement parts like output transformers have always been difficult if not impossible to find.

    The result was that when you'd hot-rod one of these amps to get more power, you'd invariably blow the Silvertone OT. Then you had to replace it with a Fender OT and the amp would never sound the same. This problem continued until eventually there became enough demand for the replacement type of OT that Mercury Magnetics started reproducing them for $150 - $160 each. That was before Jack White became popular. Now that Jack White is popular, more people are hot-rodding the amps, blowing the OT, replacing them, and repeating the cycle. Unfortunately, MM won't even discount these transformers any more because even their reproductions are in short supply. There seems to be an era of supply-demand imbalance developing all over again.

    Now the amp has become so desirable that Mojotone is even offering a Twin Twelve clone kit, in a Marshall-type chassis, with Heyboer reproduction transformers, for $750 or so. Even Jack White is reportedly using them. The good news is that now that Heyboer is making reproduction iron we're no longer stuck with a single supplier.


    Juan makes a really good point -- hot-rodding these amps is just dumb. If you need more power then add speakers. If a 2x12 isn't getting loud enough, the easy, effective, no-risk solution is to go to a 4x12, not to try to hot rod the amp to increase it's power output. For some reason people seem to miss out on the fact that the weak point in the chain of producing volume is the speaker / air interface. The acoustic power output of speakers being driven by a 50W amp is poor, on the range of only a few watts. If you really want to move some air, the answer is best achieved by focusing on speakers, not on tubes. The need for tube watts is vastly over rated.
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

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    • #17
      I pointed out the mods that I did to my brother's amp for sake of completeness, but I also said his amp was modded already and missing the reverb tank etc so it was a good candidate for mods. These amps are a PITA to work on compared to Fenders and there are diminishing returns the more mods you do. For the time and effort and money you spend on all of that, you could build a kit or your own amp with a lot less hassle. The 1484 I have for myself is completely stock and I plan to leave it that way as it is a pristine example with all the parts there and everything works. I'm with you on not modding these Bob P unless the amp is already missing stuff or has been modded. Though I do recommend to upgrade the bias circuit as I mentioned above, and some modding will have to be done to replace the can cap...either with a custom can, or a can and discrete caps, or discrete caps entirely. As I said above, uprading to more power is not a very good choice as with stock parts you can really only get to 30 watts...but if you use more efficient speakers and more speakers then you can get a very loud amp that should keep up with any good drummer who has a sense of dynamics

      Greg

      Greg

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