Attenuator for Super Reverb?

Discussion in 'Amp Central Station' started by jonhart, Apr 9, 2020.

  1. jonhart

    jonhart Tele-Meister

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    Hi everyone,
    I'm looking into getting an attenuator to drop stage volume a bit and maybe for messing around at home. I don't plan on cranking the amp, just trying to get it working a bit and keep the volume reasonable. I own a couple 4 ohm 50 watt heads and two Super Reverbs. Is there anything reasonably priced that could work with all of those amps? I haven't been able to find anything with a 2 ohm load.

    If such a thing doesn't exist, would it be okay to disconnect two of the speakers in the SR and run it into a 4 ohm attenuator? I've run SRs into 4 ohm cabs for recording, but I don't know much about attenuators and if they absolutely have to match the OT on the amp. Any advice and suggestions on what to look for would be appreciated.

    Thanks,
    Jonathon
     
  2. uriah1

    uriah1 Telefied Gold Supporter

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  3. wabashslim

    wabashslim Tele-Afflicted

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    Remember he said "reasonably priced". By the time he bought that Weber and a good attenuator he'd be sliding into "good used small tube amp" territory....much more appropriate for home use.
     
  4. johnDH

    johnDH Tele-Meister

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    If you are up for a home-build project then I can help. Our reactive attenuator design on the Marshall forum is very adaptable and has been built successfully by many guys now over the last 18 months. Its generally worked around more standard 16 and 8 ohm spec, but adapting to other numbers is just a scale factor on component values. Plus, with the attenuator, you can safely make a step change from amp tap to speaker ohms.

    Depending what you need, you can build more or less of it, starting with just a single fixed attenuation step. Or, a fully specced all-bells-and-whistles version runs about $100 in parts.

    Check it out here:

    http://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

    Its now a huge ongoing 43-page project thread with many build reports, but the basis is in the first post with a pointer to a more recent update.

    John
     
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  5. EspyHop

    EspyHop Tele-Meister

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    The Doctor doesn’t recommend the the Brake-Lite for Supers since it only works with 4/8/16 ohm speakers/cabs, not 2 ohms like Supers.

    Weber makes one that can handle 2 ohm loads.

    https://www.tedweber.com/mass
     
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  6. nocastermike

    nocastermike Tele-Meister

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    Supers are very tough to attenuate. I have a webber mass. It was ok on the super..not great. I pulled v1,disconnected a speaker and that helped some too. A super is a large and in charge beast. A vibrolux is the logical step down.
     
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  7. uriah1

    uriah1 Telefied Gold Supporter

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    Ya. That is why you need ohm swapper also
     
  8. johnDH

    johnDH Tele-Meister

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    I've looked at the Weber schematics that are posted online. Now it could well be that the real current versions aren't the same, since understandably, Weber doesn't post them and they are drawn by others. But, every one I've seen, representing either the smaller versions or the bigger ones works basically the same. The core design is based around 16 ohms with the speaker motor, and adjustment for 8 or 4 or 2 ohms is by putting resistors across the front end. When this happens, it gets a lot closer to being a resistive attenuator. If you take a 16 ohm circuit and add resistance to bring it down to 2 ohms at the front, then it is 87% a resistive attenuator. Still safe and it would work, but the magic sauce has been diluted.

    Plus, these added resistors take up most of the power, adding attenuation. Also not a problem if you need to use a significantly large volume drop, since you can just turn it back up downstream. But at 2 ohms, it seems like the lowest attenuation (ie loudest output)will be -9db plus the minimum from the main circuit so maybe -12db or more.

    Also, the output wiring is basically an L-pad, adding more damping as you turn down, so losing top end and resonance on your speakers. The tone switches are a work-around, but which also change impedance at high frequency.

    All of that is just how I see it and im happy to be corrected.

    But id say there is no free lunch with attenuators. Full performing impedance matching is usually done with transformers, and some of the more expensive designs have these. But, there are ways to keep the tone using various speaker ohms if you can accept some variation in attenuation range and work with one amp tap, or add extra reactive elements at the front.
     
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  9. jguitarman

    jguitarman Tele-Afflicted Silver Supporter

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    I've used a Dr. Z Trainwreck AirBrake 100w with my Super Reverb with no issues. I've played gigs and it has been great. They can be had for about $200. used.
     
  10. The Ballzz

    The Ballzz Tele-Afflicted

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    @jonhart

    While the linked thread is very long and still a great read (if you like technical stuff) most of the info you need to build a really good and safe for your amp attenuator is on the first page and then the lower amplifier impedance mods have coincidentally just been addressed recently on page #43. This attenuator design works so well that I call it the most liberating piece of gear that I've ever owned in +50 years as a gigging guitarist! Fairly simple, easy and inexpensive to build.

    http://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

    Just Sayin'
    Gene
     
  11. SoK66

    SoK66 Tele-Afflicted

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    I use a 2 ohm THD Hot Plate with my '68 SFSR. It was the only 2 ohm I could find at the time I bought it back in the 2000s, there may be others out there that are better. It does the job.
     
  12. jguitarman

    jguitarman Tele-Afflicted Silver Supporter

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    I need to make a correction.
    The 2 Ohm THD Hot Plate mentioned above is what I used with my Super Reverb. Sorry for the error. I have the Trainwreck and have used it with other amps like my Deluxe Reverb. The THD 2 ohm was used with the Super Reverb. Didn't want to post anything incorrect.
     
  13. vintagelove

    vintagelove Tele-Meister

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    BFSR + Fryette power station = WOW
     
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  14. Rufus

    Rufus Tele-Afflicted

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    I bought the Weber Mass for my '71 SFSR...I think it does fine, as long as you're not trying to bring a 40 watt amp down to whisper bedroom levels without losing anything.
    The main factor was the switchable ohms (e.g. 2,4 8, 16)

    Even my 5 watt late 50s Fender tweed Champ can be loud enough to attenuate, sometimes.
     
  15. jonhart

    jonhart Tele-Meister

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    Thanks for the replies everyone! @johnDH, I might go ahead with the project you have there. The Weber Mass seemed promising, but the fact that its likely designed around resistor adjustments and will drop the volume significantly is a deal breaker. I want something that just tames the amp a bit. I'm still playing on stage with drums, bass, pedal steel, loud monitors, etc...
     
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  16. johnDH

    johnDH Tele-Meister

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    I just put up a design on my Marshall forum thread, for an attenuator with fully reactive circuitry at 8, 4 and 2 ohms input and output.

    I think it may be great for your 4 Ohm heads, into 4 ohm speakers it has a minimum attenuation of -7db, so 50W goes down to 10W. If you need less attenuation, you can use it as a load box (set to max attenuation, no speaker) in parallel with a real speaker, then it will absorb half the power. So maybe you can rig up 8 Ohm speakers, with 8 Ohm load box in parallel and run from a 4 Ohm amp tap.

    For a 2 ohm amp tap, its min attenuation is about -10db, is that too much attenuation? 50W becomes 5W. Or, use it at 4 ohms as a load box, in parallel with a 4 ohm cab, to get -3db ie half power.
     
  17. radiocaster

    radiocaster Poster Extraordinaire

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    That's way too little, you'll still need to blow eardrums to crank it all the way. I guess it might be o.k. if the clubs are pretty big and the soundmen don't care, in a small club it probably won't do.
     
  18. johnDH

    johnDH Tele-Meister

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    If so, then it's all good, by minimum attenuation I mean that's the loudest attenuated setting. From, there you can step down quieter in small steps down to -31db or less
     
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  19. dan40

    dan40 Tele-Afflicted

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    I can also attest to John's attenuator design. I built mine as a resistive unit when the thread first started and then finally switched it over to the reactive version about 6 months ago. It works so well that I sold off my Weber mini mass and now use this one exclusively.
     
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