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SVP Problem - Yep, already!!

Discussion in 'Amps and Cabs [BG]' started by Gabu, Dec 30, 2002.

  1. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    Anyone else have a problem with HF noise coming from their SVP? I had thought there might be a problem with the horn on my Avatar 12, because it makes a very audible hiss when I use it, but I do not have that issue when I plug into my SVT400T.
  2. rok51

    rok51 Supporting Member

    Sep 2, 2002
    Crawfordville, FL
    Yes, the preamp can be a little "hissy", especially with a HF horn in the cab. Shouldn't be noticeable in a band context. If it really bothers you, consider getting a noise gate.

  3. Ncognito

    Ncognito Banned Commercial User

    Jan 8, 2002
    Hoffman Estates, Illinois
    Owner, Xsonics Bass Cabinets
    Did you buy it new. The older ones hiseed like a snake, but the new ones have an improved D.I. and much less noise.
  4. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    Hmm... I don't slap much... I actually hardly know how to. It does bug me a bit to have limitations... Right now I have the horn turned off.
  5. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    Yep, I bought a brand new one. It sounds awesome, I just don't dig the hiss in the horn. On one hand I probably don't need it... But I dunno, for some reason it just bugs me. :(
  6. My setup makes a bit of a hum, but seems to be related to where I play though. I don't have horns on my cabs (Ugh, always turn em off at the stores), so don't know about that. My poweramp burns coal as a power source, so that could be it. But everytime I've used it to record or live, it's been a quiet as could be. Maybe just dirty power?

    Mmmm...SVP. Yummy.
  7. Cantstandsya

    Cantstandsya Supporting Member

    Jul 27, 2001
    Fontana, CA
    Could the hiss be the awful raspy sound you get when you put certain overdrive/distortion sounds through a horn or are you running it clean?
  8. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    It could be overdrive. I have an overdrive knob on the SVP, but I haven't fiddled with it too much. Is that a likely culprit for the horn hiss?
  9. geshel


    Oct 2, 2001
    Does it hiss all the time, even when you're not playing? I think the overdrive comment was just about the distortion going through the tweeter.

    When I first got my Clarus I noticed it hissed quite a bit through the Peavey 210tx. Through the Acme and EA cabs it's not noticeable though. I think it's a bit higher hiss in the amp, plus over-accentuated highs in the speaker, together.
  10. Rockbobmel

    Rockbobmel Supporting Member

    Could it be the preamp tubes?
  11. It sure could.

    SVP-PROs hiss a tiny bit. Mine is pretty darned quiet - even when connected to my RMX2450.

    There are only three things that can go wrong with an SVP. One of them is tubes.

    The second thing is also tubes. ;)

    The third thing is a bad solder joint on the edge of the circuit board but this usually causes hum, not hiss. The amp has a five-year transferable warranty.

    My unsolicited advice?

    Unplug everything except the preamp --> power amp connection. Take everything out of the effects loop and unplug the bass. Does it still hiss?

    If not, it ain't the preamp. Now run the power amp alone - if it still hisses it ain't the preamp.

    Next, get a known good 12AX7 and a spare instrument cable. Take the preamp out of the rack and connect it to the power amp with the long instrument cable. Turn the drive control all the way down and swap out the tubes one at a time with the known good one. If it's a tube causing the hiss it'll shut up when you replace the bad one. Remember the tube in socket #4 (second from right) is a 12AU7 but you can use a 12AX7 for testing if you don't crank the drive control.

    A good set of tubes can make all the difference in the world - and my personal opinion is the SVP-PRO doesn't ship with a particularly great set of tubes.
  12. VicDamone


    Jun 25, 2000
    Does your system hiss with the preamp off amp on?
  13. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    Thanks for the great advice all. I am going into the garage to check out the things I can try right away, and then I will post again. As always, you guys rock!! :)
  14. Dont' let this happen. The same thing happened with mine. I took it to an authorized service center, and they found that 3 of the tubes were bad. I got it back, with 3 new tubes, and only minimal noise, at Ampeg's expense.

    Take it to a certified service center; dont' waste your own money replacing dead tubes that shouldn't have shipped with it.
  15. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    are you using balanced or unbalanced cables to hook it up? that could be the difference...
  16. er, um, I think we're talking about a few inches of cabling here; not sure if balancing would make a difference.
  17. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    it did with mine...:)
  18. Gabu


    Jan 2, 2001
    Lake Elsinore, CA
    Unbalanced cables.

    I tried some things... so here is what I learned so far:

    1) This hiss comes from the horn, and is audible with a 25% turn of the horn knob on the back of the Avatar 12 cab.

    2) The hiss does not occur with my other amp. (Ampeg SVT400T)

    3) I connected the power amp to the cab in question by itself. That created no hiss.

    4) I connected the SVP by itself, and that created no hiss.

    5) The his exists with any of my basses.

    6) If I turn the tone control off completely on any of my basses the hiss goes away.

    7) It increases as I turn up the "drive" knob until it gets to about 66%, then as you continue to turn the drive knob it decreases slightly. But in any case, the drive knob does not make a large impact on the hiss.

    8) I have tweaked all of the knobs, and the EQ and not learned any combo that would significantly decrease the hiss.


    Thanks very much for all of your help so far! I am hoping I won't have to take it out for service... But Maybe this should be nipped in the bud. This hiss is way too loud to be normal. Do you all think it might just be the nonbalanced cable?
  19. Dude, I'm telling you, it's the tubes. The same thing happened to me.

    Is there an authorized service center near you?
  20. seamus


    Feb 8, 2001
    Are these the stock tubes that ship with the unit, because I must say, I found those to be quite noisy when I first got the thing. I can't recall what sort of noise exactly because I switched them out so quick, but the noise floor was definitely unacceptable upon arrival.

    The first replacements I tried were EH tubes all around. I was very pleased with them, as they are very quiet, and sound good to me. I have some other tubes I haven't tried in there yet too, but I'm too lazy to pop it out of the rack and remove all the chassis screws again. :p

    Not sure if noisy tubes is what's got you down here, but I can say the EH tubes were pretty cheap when I bought them. I think I retubed the whole unit for $40-50, including the 12AU7. Good luck with solving the problem.

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