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Thread: Speaker driven reverb

  1. #1
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    Speaker driven reverb

    Working on an old Ampeg Super Echo Twin, ET-2 that has the reverb tank driven by one of the speakers like other old amps.

    Got it working great but, this is such an easy cheap way to do it, why did amp makers get away from it?

    I think I need to try it for something I'm toying with.

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    One reason is because if the amp itself was turned up too loud, it distorted the reverb too. So if the signal was clipping, then went to the reverb tank, well, what's a clipped signal then sent to a reverb circuit which was probably also sent into overdrive...

    Ampeg's founder HATED rock & roll & distortion, even kicking bands out of the factory who's sound he didn't like.

    Put up a schematic! If it's anything like I'm thinking, it's kinda like one of those "speaker-driven" line-outs - if my Bassman is crunching away happily, so is it in everybody's monitors.

    Justin

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    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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    Bent Member Chuck H's Avatar
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    Well... I think it's significant to note that this is a stereo amp. A rarity really. One of the channels feeds the reverb and the other recovers it. In a self contained amp this is about the only way it can work. The rarity of the stereo format for vintage amps would explain the lack of this MO for reverb circuits.

    I built a dedicated reverb amp for a customer that filches power from the host amp to drive the reverb tank. It works great. It reverberates the sound of the WHOLE amp. It's especially nice when the host amp is overdriven because then THAT tone is reverberated rather than, as would be the case with mono amp built in reverb systems, the reverberated tone being distorted. But short of a dedicated amp for the purpose or a stereo amp with one channel pitching and the other channel catching it's not practical for mono amps. I think the Fender Champ 12 used a power amp driven reverb that used frequency and phase differentiation to skirt feedback problems within the closed loop circuit. IIRC it's reported to sound thin, weak and behave problematic.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

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    Old Timer olddawg's Avatar
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    More than once Iíve had people bring me an odd guitar amp to fix and I have had to tell them it isnít a guitar amp... itís a Reverb amp. The most common was a Maestro (Gibson), but there were others. They connected to the speaker terminals of any combo amp with alligator clips. Itís basically an extension amp with a Reverb tank driven by the speaker signal of the other amp. Many times the ďclipĒ cord gets cut off or falls off an people donít understand why the amp doesnít work with a guitar plugged into it after they install an input jack.

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    Quote Originally Posted by olddawg View Post
    ...it isnít a guitar amp... itís a Reverb amp.
    I have one of those. It's of Valco manufacture, but the actual brand logo is missing -- probably a Supro. It's dang cool looking -- I'll take a picture and post it next time I run across the thing.

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    -tb

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