New (old) Ampeg svt810 input help

Discussion in 'Amps and Cabs [BG]' started by jcroxford, Mar 9, 2019.


  1. jcroxford

    jcroxford

    Jan 7, 2017
    Sacramento CA
    So I just acquired an older Ampeg SVT810 classic cab. it's pretty run down, needs new rails and rubber feet,and could use a new tolex job. The jack plate only has 2 1/4 inputs. all the writing has been rubbed off. I'm not sure which input to plug into or which input does what. With the cab I got a 79' Ampeg V-4B head. It has 2 1/4 outputs, and can has a selector switch to run the head at 8, 4, or 2 ohms.
     
  2. filmtex

    filmtex

    May 29, 2011
    Picture of the input jackplate would be helpful. For me at least.
     
  3. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    The old cabs couldn’t be split like the newer cabs so likely it’s two parallel jacks. Check it with a meter if you have one, or with a 9V if you don’t.

    On the V4B use the “main” speaker out first, extension out if you’re running multiple cabs in parallel. The main out shorts to ground if you don’t have anything plugged in.
     
  4. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    If you can post an image of the jack plate, it would be easier to see what is going on. The plate might not be original. Below is an example of one. There were variations over the years.

    jack plate.jpg

    Also, it would help to see what was done if you pulled the screws and posted an image of the wiring.

    Chances are, the two jacks are simply wired in parallel with two wires connecting to one of the jacks. It can be more complicated with switching going on.
     
  5. jcroxford

    jcroxford

    Jan 7, 2017
    Sacramento CA
    20190310_104817.jpg 20190310_104817.jpg
     

    Attached Files:

    beans-on-toast likes this.
  6. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    I can't see the wiring in enough detail to figure out what was done.

    This assumes that the speakers are original 32 ohms each. There are two ways to wire an 810 with jacks.

    The first is to wire the speakers in parallel, that is, all the [+] together and all the speaker [-] together. Then the speaker [+] connects to the jack tip, the speaker [-] connects to the jack sleeve (ground). If a second jack is present, the two jacks are connected in parallel for daisy chaining.

    The second approach is to be what you seem to have. The top four speakers are connected in parallel, connect the speaker [+], connect the speaker [-]. Same is done with the bottom four but the top and bottom are kept separate. This gives you four wires comming off, a pair each from the top four speakers and a pair from the bottom four speakers. This wiring is show below and the four wires can be seen in your image.

    SLM 810 wiring.jpg

    The wiring on the jack plate connects the top four speakers (8 ohms) and the bottom four speakers (8 ohms) in parallel, to provide a total of four ohms. The two jacks are wired in parallel so that daisy chaining can be done. But I can't verify if this is what was done from your images.

    Some 810 revisions used a shunt on the jack to switch connections so that the top four speakers can come out one jack at 8 ohms; the bottom four speakers out another jack at 8 ohms. A third jack is often used to switch the cab to mono when a plug is inserted, all eight speakers are connected in parallel for a total of 4 ohms.


    My concern is that the cloth covered wires in your image are not what I've seen before. This makes me wonder if your cab has been rewired in some way. I'd want to pull the speakers and draw a diagram of the wiring, also verify that the soeakers are 32 ohms each. A concern is that when doing this there is always a concern that you could put a screw driver through the speaker cone.
     
  7. jcroxford

    jcroxford

    Jan 7, 2017
    Sacramento CA
    Not sure if this helps, but I snapped this one as well 20190310_104810.jpg
     

    Attached Files:

  8. jcroxford

    jcroxford

    Jan 7, 2017
    Sacramento CA
    Is the Jack on the right stereo? There is solder on the top lead, but no wire connected to it
     
  9. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    Still can’t tell. I’d need a drawing, what wire is going where.
     
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