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4 1/2 OHM CABS - blown Ampeg SVT ???

Discussion in 'Amps and Cabs [BG]' started by Jonesy4fnk, Apr 10, 2003.

  1. Jonesy4fnk

    Jonesy4fnk Supporting Member

    I'm running and Ampeg SVT-IV head though two Carvin RL2X10 cabs. They are rated at 4 1/2 ohms and 400watts each. The Ampeg is rated 490 watts RMS @ 4ohms per side.

    My Ampeg has blown both sides of its power section on 2 different occasions. Both times the repair tech bench tested for over a day and it ran great for months then came unbiased and blew. Now its blown again and I'm debating just buying another one. But I want to avoid the problem in the future so......

    Could the 4 1/2 ohm loads on each side be causing the power sections to wear and blow. I run at high volume usually but haven't notices any other problems.

    Any ideas?
  2. Jonesy4fnk

    Jonesy4fnk Supporting Member

    oh yeah also - I use a Carvin R1000 head for a backup and it seems like it gets pretty hot quicker than normal when I run the 2) 2X10 setup. It is also a 2 channel power amp.
  3. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Hm, I'm confused by your "4 1/2 ohms", cabs are rated in full numbers, e.g. 3, 4, 6, 8 or 16 ohms.
    This is only a category, impedance is not a fixed value.

    How do you hook your cabs to the amp?
    My suspicion is that you daisy-chain the cabs, thus putting a 2 ohm load on the amp.
  4. Jonesy4fnk

    Jonesy4fnk Supporting Member

    the cabs are listed as 4 1/2 ohms on the back of them and on the Carvin website. I've never seen it before either.

    I'm not running them in series. The svt-4 has 2 channel outputs, I run one 2x10 from each side (so 4 1/2 ohms at 490RMS per side) If I ran both cabs off parallel off of one side it would be a 2 1/4 ohm load I believe. If I were daisy-chaining them in series it would make the load 9ohms right?
  5. BruceWane


    Oct 31, 2002
    Houston, TX
    You'd have to do some custom wiring to run your cabs in series. Daisy-chaining puts them in parallel.

    You might want to call Carvin and ask them what the impedence of your cabinets should be when measured with a meter and check yours to make sure you don't have some defective drivers with excessively low impedence. The resistance reading you'll get from a meter will be different from the specified impedence - I'm not exactly sure, but the specified impedance is more like an average of the speakers resistance over its frequency range.
  6. Trust me, they're not 4 1/2 ohm cabs, they're 4 ohm cabs. My guess is that some bug in the HTML rendered a Greek capital omega, the symbol for ohm, as a 1/2. Or the font they used didn't have Greek letters in it. This kind of thing happens a lot with Greek letters. The error could then have been replicated when they printed up the backplate for your cab. You notice that on the website it doesn't say 4 1/2 ohms, it just says 4 1/2. If you pull up the .pdf of the manual, you see that it gives the nominal impedance as 4{omega}, not 4 1/2 anything.

    You might have defective drivers, so that the cab impedance is lower than it's supposed to be. But you'd think that with a well-designed amp, that would just cause it to shut off rather than blow up. The really techy guys around here might have some better ideas. The only other thing I can think of offhand is, how's the power where you play? Are you maybe trying to run off too low a current? Also, you say you run at high volumes, and those Carvin cabs are not hugely efficient. Are you maybe trying to push them a bit hard? Again, though, I don't know that either of those would make an amp fry rather than shut down.
  7. Petebass


    Dec 22, 2002
    QLD Australia
    I don't know what the specs of the SVT-IV are, so I did a quick search and found this website .

    Is this the same as your amp? If it is, you'll notice this one is rated at 1200w at 4 Ohms minimum. You appear to be running a 2 ohm load which would explain why the amp keeps frying.
  8. SnaveDogg


    Mar 21, 2003
    Birmingham, AL
    If you click on the "manuals" icon on the same page as the product description for the cabinet, it will display a PDF file for the owners manual. Specs are on the lower right section where Nominal impedance is listed at "4 ohms".
  9. I think this is what Jonesy has got:

    Dimensions : 19 x 5.25 x 15.5
    Weight : 42 Pounds
    Preamp (Tube or SS) : T (3 x 12AX7)
    Driver Tubes : n/a
    Power Amp : MF
    RMS Power Output (8 Ohms) : 300x2/900 (mono-bridged @ 8 Ohms)
    RMS Power Output (4 Ohms) : 490x2/1200 (mono-bridged @ 4 Ohms)
    RMS Power Output (2 Ohms) : 600x2
    Tone Controls : 3 band
    Mid Tone Control : 5 pos
    Graphic EQ : 9 band
    Ultra Low/High Boosts : Yes
    Balanced Line Out : Yes x 2 (Transformer)
    Effects Loop : Yes x 2
    Preamp Out/Power Amp In : Yes x 2

    Other Features: Input Peak LED
    Dual 1/4\' Inputs
    -15 dB Pad
    Variable 0 - 7:1 Compressor
    Bright Switch
    Nine Band Graphic EQ
    Defeatable Optocoupler Limiters
    Internal 24 dB/Octave Crossover
    Linkwitz-Riley State Variable Filters
    50 - 1KHz Variable Crossover Point
    High/Low Balance Control
    Tuner Out Jack
    Mute Function
    1/4\' Biamp High and Low Outputs
    AC Convenience Outlet
    15 Amp Circuit Breaker

    So it really seems as if his setup ought to work. I got no clue here what's wrong.
  10. rumblethump

    rumblethump Supporting Member

    Mar 25, 2000
    Pioneer CA. 95666
    A friend of mine has the same amp. It spent more time in the shop than he's had it. It went back twice for repairs and they kept it months at a time.
    He loves the power and tone, but after his problems, I wouldn't touch one with a ten foot pole. :bag: It you PM me I will give you his e-mail addy.
  11. Jonesy4fnk

    Jonesy4fnk Supporting Member

    thanks for all the advice. It doesn't make sense, even if it were operating at 2 ohms, it should handle it fine according to the specs.

    I love the tone but it has soured me to Ampeg.

    Maybe time for alternatives.
  12. Jonesy4fnk

    Jonesy4fnk Supporting Member

    I'm not running it bridged though, just stereo which it should be able to handle.
  13. cb56


    Jul 2, 2000
    Central Illinois
    My Carvin 210 says 4ohms 400 watts. I run my carvin 210 on one side of my Ampeg B4r (350 watts x2 at 4 ohm per side)and an Ampeg 610 hlf also (4ohms) on the other. never had a problem with either the speaker cabs or the amp.
  14. It sounds to me as though something is crapping out in the amp. As somebody already said, any well designed amp should go into thermal shutdown before blowing. It is a fact though that some amps don't work well with some speakers. (Acme b2 4 ohm with a Carvin DCM1000) for example. One thing is for sure, you can't keep on doing what your doing. Good luck.....
  15. Jonesy4fnk

    Jonesy4fnk Supporting Member

    No doubt about that.

    I've emailed Carvin to see what they think but I believe its in the head. We'll see when it gets fixed this time what the tech says. He's good, no problems until this amp.

    Maybe those RL210s just don't workout with the Ampeg or something. I think I'll start using my Ampeg PR-410hlf cab instead of the 2x10s when I get the amp back. If it works out, I'll know the culprit. Its a good excuse to get another cabinet for smaller rooms :rolleyes: Maybe Aguilar or Berg 212.

    If I find the problem I'll post it.

    I'm thinking that getting a voltage meter power conditioner to check the different room's power. It may be a factor with such a high powered amp, any fluxuation could be damaging.
  16. Jonesy4fnk

    Jonesy4fnk Supporting Member

    from Carvin

    ."The RL210T's should be a perfect match for that amp. They are 4 Ohms each and can handle the power. You are right, you could just be pushing it too hard. You can't drive a car at redline continuously, or something will give. Sounds like maybe you need more power and more speaker area for the volumes you desire."

    so I guess its the amp, possibly from me cranking it