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Early '70s Magnavox SVT sounds disappointing?

Discussion in 'Amps and Cabs [BG]' started by jwhjwh, Dec 20, 2012.

  1. jwhjwh


    Dec 20, 2012
    Hi everybody,

    A few months ago, after blowing out my B2RE, for the third time (I seriously think that amp is haunted), I remembered that my friend's father had a vintage SVT in his garage. I remembered this because I had asked to buy it from him over a decade ago, and he had insisted he was going to fix it up at some point. Ten, twelve years later, I asked him again, and to my surprise he agreed to sell the amp to me.

    It was in truly miserable shape- having been left in a garage for twenty years, and at one point having been used alternately as a doorstop, and to prop up a rainwater collection bucket. Nonetheless I was excited- if my amp guy could fix it up, I'd have the holy grail of rock amps, right? At least, that's what I had hoped.

    After two-hundred bucks for new 6550s, and another two-hundred for miscellaneous caps, pots, labor, and the like, I was finally ready to hear what this thing sounded like.

    I know this is sacrilege to say, but it just didn't sound that great! I tried playing through an Ampeg 610HLF, as well as a Marshall VBC412, and in both cases, the amp sounded extremely loud, but almost in a way that I couldn't hear. I kept turning up, hoping to find a flatter response, but it just wasn't there.

    It's difficult to explain- adjusting the various rocker switches and tone knobs produces a sound that went from muffled and deafening to ice picky and deafening, but with very little else. In the case of the former, it was almost like a stack of pillows was in front of the amp. In the case of the latter, it was like a guy sitting on those pillows and poking you in the face with a kitchen knife.

    I realize this must sound crazy, but is this just the nature of the beast? I'm perfectly happy to accept that this is just how they sound, and it either works or it doesn't. I'm just surprised- I guess I was expecting some revelatory experience with angels and trumpets.

    Any thoughts?
  2. The amp still has problems not addressed/missed by your tech. PERIOD. The amp should not sound that way at all. If he replaced all six output tubes the driver tubes may also be faulty just as an example. It also sounds like the mid circuit is almost dead.
  3. jwhjwh


    Dec 20, 2012
    All new tubes, actually- across the entire chassis. Spending twenty years in an unheated garage in New England is apparently bad for tubes, I guess.

    The tone controls definitely work, though I can't speak to the circuit.

    In fact, it sounds very similar to my 70's V4B, but not quite the life changing experience I was hoping for.

    If I have my tech look at this amp again, is there something specific you'd recommend I ask him to investigate?
  4. GreaserMatt


    Sep 4, 2004
    Seattle, WA
    Dude, that is the holy grail of bass amps; there is something amiss with that thing. Maybe have someone else dial it in for you? That amp is THE amp all other bass amps strive to be, IMHO...
  5. JOE EDO

    JOE EDO Supporting Member

    Aug 28, 2007
    Central New York
    I have a 73 that was also "thin" and "boomy" when I found it. Check the caps in the preamp. You said miscellaneous caps too....why not all? If it's been laying around and abused good practice to replace all. Did the tube sockets get re-tensioned when it was in for service? Did the tech hook it to a dummy load and scope it for output? You really have to think through the entire signal path of these old amps front to back. Be patient and it may cost you a bit more to get it where it needs to be. In the end it is worth it.
  6. Bass select switch, Mid select switch, midrange toroidal for opens. Did you get new production 12DW7's or did he sub 12AX7's? The 6C4's are a known problem, a nicely quiet one is usually a bad one. Be sure the bias and balance are correct on the output tubes.
  7. jwhjwh


    Dec 20, 2012
    It's funny, that's what everyone says, and what I had always believed as well.
  8. jwhjwh


    Dec 20, 2012
    New production 12DW7s.
  9. Where are you located?

    New production 12DW7's are a crap shoot. I usually throw out about half I get.
  10. 4StringShooter

    4StringShooter Banned

    Jun 26, 2011
    London, Ontario, Canada
    GBX Member #1
    Some " say " it is the " Holy Grail " of amps, but I SOLD mine......

    I dont agree.
  11. jwhjwh


    Dec 20, 2012
    I'll have to ask him for a more detailed account of what was replaced. He handed me a very large plastic zip-lock bag full of the components he replaced. There are an awful lot of caps in there.

    Same goes for the tube sockets- I'll have to ask.

  12. jwhjwh


    Dec 20, 2012
    I'm in Western Massachusetts.
  13. I don't have any names to offer over and up there. Johnk_10 (west coast) is also a good resource for trouble shooting. The V4-B has a sweeter low end, the SVT should have more thump , low mids and upper mids. Very present sound that cuts a mix well.
  14. jwhjwh


    Dec 20, 2012
    That's very interesting to hear, because tonight at practice I was so deep in the mix as to be invisible.

    I kept turning up and up, and my guitarist insisted it was deafening, and I insisted I couldn't hear myself!

    Do the vintage SVTs have a really pronounced mid scoop? I've been finding conflicting information all over the place about their tone stack. Some people insist the Ultra Low switch should be avoided at all costs, others seem to have no problem with it. Some people think the amp has a very pronounced mid scoop, others insist it has too much mids. It's hard to know what the consensus is.
  15. eyeballkid

    eyeballkid Supporting Member

    Jul 19, 2009
    wes virginny
    turn all switches off. put everything at noon. play it. adjust to taste.
  16. JOE EDO

    JOE EDO Supporting Member

    Aug 28, 2007
    Central New York

    Don't let other people sway you. Put on a good set of headphones, close your eyes, and listen. Then decide for yourself.
  17. This defines loss of mids. Ultra low switch, not a fan.
  18. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    Umm ... no. He should have tested them. If he didn't give you the old ones back he probably sold them for big $$$ as good vintage tubes are quite valuable.
  19. jwhjwh


    Dec 20, 2012
    I found this youtube demonstration of a similar era SVT:

    That's more or less exactly the tone I'm getting.

    I don't know, perhaps it's just not the right tone for this band. Or I need to get my hearing checked. Or both.

    Nevertheless, thanks for all the help guys, very much appreciated.
  20. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    That's a single 15 with no tweeter I believe - not what your 6x10 should sound like.