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"Out of phase" situation in "Dual Amp" setup

Discussion in 'Amps and Cabs [BG]' started by JaySeeDoubleYou, Oct 7, 2010.


  1. Hey Guys!

    Didn't see an existing thread that deals directly with this: I'm just beginning to dabble with "dual - amp" setups. The one amp is a 2007 Fender Bassman 250/2-10 solid state, closed cab combo amp. Not real high end, nothing to get excited about, necessarily, but not a budget basement amp either. Very modern tone with a fair smattering of modern features. The other amp is a 1967 Sears Silvertone 1483 all-tube bass amp (made by Danelectro). It's a separate amp and head, though the head fits in a cavity in the back of the cab, resulting in a psuedo-open back cab. The cab contains a single 15" Jensen paper cone speaker.

    If the Bassman has a very modern tone, the Silvertone has a -very- retro tone. Very mid-heavy, very highly defined tone, much more personality than the fender, but less high end, and a relatively thin bottom. Also, since it's only a 23 watt amp, it begins to go into tube distort pretty early on the dial (about 9 o'clock), though because it's tube, it still manages to be plenty loud for a home studio environment.

    The Fender is very well rounded with big bottom, bright highs, and the crystal clarity of solid state, but by itself doesn't have much "personality", it's kind of bland. The silvertone has got awesome personality, great definition in the midrange, and that bad-boy tube grow, but by itself is fairly lacking in the low end, and overdrives way too easily, and too heavily. But the two combined create a really neat sound. I usually keep the volume just a little bit higher on the Silvertone so that it's slightly dominant. It really creates a best-of-both worlds sound.

    Blessedly, I've avoided the whole grounding issue, my two amps play nice together that way without hum or buzz, but I am falling victim to the whole "out of phase" issue, it appears.

    Even with it out of phase, it doesn't sound "bad" per se. I can still hear the benefit of having the two going in tandem, but I am losing a lot of low end, almost all the low end out of the fender (though I'm keeping most of it out of the silvertone. On balance, I have maybe a little bit more bass than I did, but a whole lot less bass than I should under the circumstances), and the horn tweeter on the bassman seems just a tad "out of sync" with the big 15" cone of the Silvertone, (which is only really noticable when you're using "echoey" effects.) I would like to shore this problem up, though, so that I can take full advantage of the "marriage" of these two amps.

    I've been told that fixing the out of phase issue between amps is as simple as taking the positive/negative speaker connections on one or the other of the amps and swaping them. Therefore, positive is negative and negative is positive, reversing the phase on that amp so that it accords with the phase on the other amp. Makes sense to me.

    So, the Bassman is an enclosed, carpetted cabinet with front screw access (I'd have to take off the grates, pull out all three speakers (including the horn driver), just hope that the connections are slide-on connections rather than soldered, switch them all, and then put the whole mess back together.

    The Silvertone is an open back cabinet, -sort of-. It's got a panel that encloses the back of the speaker, but sound escapes out of either side of this panel and then out the back.

    Clearly being the easier speaker to access, I take that back panel off the silvertone, only to find that the connections are soldered on, and more than that, there's two sets of speaker wires coming out of the speaker, one to the output cable, and another to what looks like a small power transformer mounted to the inside side of the speaker cabinet. Since it's a single speaker in the cabinet, I can't assume it's a crossover, and so I don't know what purpose it serves, and therefore, I am afraid to mess with it.

    So I figure, rather than messing with either of the cabinets, what I'd like to find instead is just some sort of cheap external solution.

    I've heard that they make a thing where if you want, say, to mic both the front and back of an open back cab, you can. If you simply set a mic on both sides of the cab, you'll get cancellation because it'd be out of phase, so as I understand it, they have a deal that's inline for XLR connections. One side of it connects to the male XLR connection on the mic, and the other side receives the female XLR connection on the cable, and what it does is it reverses the phase on that mic, so that whatever you're recording records in phase with itself.

    What I'd like to know is if they make such a beast for 1/4" guitar cables, so that anything I run out of an A/B switch to, say, the bassman, I can reverse the phase on, so that both amps are cooperating, rather than fighting each other.

    Do they make such an animal? If so, where can I score one, and how much do they cost? If they don't make anything like this, do you guys have any alternative solutions that might work for me?

    As I said, even out of phase, I can hear how these two very different amps compliment each other, and so I'm very excited to get this issue fixed so that I can take full advantage of them.

    Anybody have any great solutions? I'm all ears! :)

    Thanks guys!

    God Bless!

    -J
     
  2. hrgiger

    hrgiger

    Jan 11, 2009
    That was a pretty good one man- you had me going for a while. :D
     
  3. Nope, dead serious. Anybody have any suggestions for how to fix this phase issue (that doesn't involve ditching them and replacing them with xyz)? :)

    I'd appreciate any help here, guys! I know it's not exactly a conventional set up, but I think it'll be a really neat one once I've got it all set up! :D

    Thanks again!

    -J
     
  4. bobcruz

    bobcruz

    Mar 10, 2004
    CA
    How do you get your instrument signal to both amps? I don't know about the product you mention but it wouldn't be too difficult to make and out-of-phase cable, or a jack in a Y-connector box, to reverse the phase of the signal to one amp or the other. You'd need to clearly label whatever you made so you don't use it accidentally when you didn't want the phase reversed.
     
  5. bass4worship

    bass4worship Ready For Freddy, let rock Supporting Member

    May 4, 2009
    Sebring, Florida
    Throw a double pole double throw switch on one of the speaker cab or both. That what I use to correct the phasing.
     
  6. smogg

    smogg

    Mar 27, 2007
    NPR, Florida
    I'm not crazy, I'm just a little unwell
    Use a nine volt battery to verify the cabs are in fact out of phase and determine which cab is out of phase. Then just reverse the wires on the input jack(s) on the cab that is out of phase.
     
  7. Reverse the connections to the Sears speaker and try again.
     
  8. Thanks for the ideas, guys.

    Paul, There's a transformer looking thing that's also connected to the speaker. It looks like a miniature of the big transformer on the inside of the amp head (on what I'll call "the tube panel"). Should I not worry about that? In other words, I'll be okay to swap the wires on the speaker input without swapping the wires on [we'll just call it] the transformer? Keep in mind that they're sharing a common solder connection to the speaker.

    I'll try to get a picture posted when I get home tonight.

    Thanks again guys!
     
  9. You know, I'm almost thinking that just making a phase reverse cable would make the most sense, because then if I want to run the amp in a standalone context back in its original phase, then it's as simple a matter as using a different cable, and switching the phase in a cable should be easy enough, just reverse the positive/negative on one end of the cable and leave the other end alone.

    The more I think about that idea, the more I like it! :D
     
  10. fokof

    fokof One day ,I'll be in the future

    Mar 16, 2007
    Here
  11. Thunderthumbs73

    Thunderthumbs73

    May 5, 2008
  12. spiritbass

    spiritbass

    Jun 9, 2004
    Ashland, MO
    That sounds like a field coil. If it actually is a field coil-type speaker, it acts as an electromagnet for the speaker and choke for the power supply. I've seen them in old radios, but not amps...
    Anyway, I agree that your best, least expensive, and safest bet would be a phase inverting cable. Your phase shift may be occurring by design in the Silvertone. I've been thinking of a split cable and playing with a Blues Junior for my bridge pickup and bass rig for the neck on my Ric, just for fun. :D
     
  13. spiritbass

    spiritbass

    Jun 9, 2004
    Ashland, MO
    That sounds like a field coil. If it actually is a field coil-type speaker, it acts as an electromagnet for the speaker and choke for the power supply. I've seen them in old radios, but not amps...
    Anyway, I agree that your best, least expensive, and safest bet would be a phase inverting cable. Your phase shift may be occurring by design in the Silvertone. I've been thinking of making a split cable and playing with a Blues Junior for my bridge pickup and bass rig for the neck on my Ric, just for fun. :D
     
  14. A Silvertone 1483 does have a coil across the speaker.

    Just desolder the wires on the speaker terminals and resolder to the opposite terminals.

    Silvertone1483.png
     

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