svt vr 4 ohm into 8 ohm cabs, ampeg say don´t do it

Discussion in 'Amps and Cabs [BG]' started by solitario, Nov 20, 2012.


  1. solitario

    solitario

    Oct 13, 2011
    Spain
    svt vr 4 ohm into 8 ohm cabs, ampeg told me not todo it but if have seen many players vith vr and svt classic with ampeg 410 he cab that are 8 ohm.

    I asked some tech and they told me that if the cab in 8 ohm and the amp 4 ohm there should be no problem.

    are all those players with ampeg valve heads and 410 he wrong?

    thank you
     
  2. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    If you run an SVT into an 8 ohm cabinet using the 4 ohm tap you are stressing the output tubes because there is not enough current to pull the voltages down and the output transformer insulation might start failing, causing the dreaded shorted turn and an untimely death.
    You can get away with it, but for how long? it sucks the power and it's a huge risk, don't do it.:bassist:
    PS did the engineer you asked get the tube amp concept or did he just give you a semiconductor based answer.
    If the latter he is right. Quite a lot of young engineers have no experience with tube technology.
     
    gsgbass likes this.
  3. solitario

    solitario

    Oct 13, 2011
    Spain
    I told him it vas a svt vr... he is supoused to know svt vr are all tube amps... I hope...
     
  4. arai

    arai Banned

    Jul 16, 2007
    +1 to Bassmec's post
    But it it is fine to do it with someone else's gear
     
  5. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    He gave you a semiconductor answer so he didn't seem to understand the concept of output transformer load matching in tube amps.
    Of course you could just check your cab and see if it is actually 4 X 8 ohm drivers in series parallel to arrive at 8 ohms total.
    which would add up to 2 ohms if you rewired the cab all drivers In parallel.
    You have an impedance tap on your VR for 2 Ohms so match it.:bassist:
     
  6. Pretty sure the drivers in the 410HE are the same 32 ohm drivers from the 810E.
     
  7. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    The he's use four 32 Ohm drivers I believe. Would have to source new drivers to get the cab to a 4 or 8 ohm load.

    Personally I would look into a different cab, way more economical in the long run.
     
  8. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    If they are, it's not going to be possible.
    do they still use 32 ohm drivers these days, I know my old CTS driver'd 8 X 10 was, seems odd because it must cost them in Ampeg only application terms. quantity ordered cost considerations.
    That's why I said if they are 8 ohms.:bassist:
     
  9. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    If you keep the volume low, you can usually use an 8 ohm cab with an SVT without incident. But it's certainly not recommended.
     
  10. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    right;

    you can run your 5-speed car on the highway in 3rd gear, but is it a good idea?
     
  11. wilfredes

    wilfredes

    Oct 11, 2012
    Would have to source new drivers to get the cab to a 4 or 8 ohm load.
    [​IMG]
    [​IMG]
     
  12. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Ampeg gave you their "official" answer. The amp should be matched to the cab for optimal performance.

    People run with the bulls. That doesn't make it safe.
     
    agedhorse likes this.
  13. ScottTunes

    ScottTunes Gear-A-Holic Supporting Member

    Feb 7, 2011
    So Cal
    In the ignorance is bliss column, I used my V-9 SVT (1976 Magnavox era) through 8 ohm cabs many times, although for relatively low volume sits... Back then I was told you could go "up or down" basically one level - meaning using an 8 ohm amp into 4 ohms, and/or a 4 ohm amp into 8 ohms (with tube heads anyway)... But matching is the best option.
     
  14. D Rock 247

    D Rock 247

    Dec 24, 2016
    I just had this same problem on a mesa bass prodigy. (Amps and cabs section -blew a kt88....) the manual called for a 4 ohm tap to a 8 ohm cab (this amp has a half power switch which drops it to two kt88s as output) and i blew a kt88 and a fuse with this setup. Now everyone was giving me crap about blowing a kt88 but i was following procedure via prodigy manual- setup. But i can almost see the relation on your comment on stressing the output tubes- weather or not if its a svt, mesa, whatever. Even if it calls for it on half power. Anyway, got the problem fixed and only now running full power (no more half power playing) and for now havent tried my 8 ohm 212 again (cab used when the tube blew up) but i do have an 8 ohm tap from the amp to the 2x12 cab. No issues at all on half power or full power on my svt 6x10. But just wondering what u think of my situation cause everyone on my kt88 thread, was just beating around the bush and i dont think hardly no one that stuck their nose in my thread even knew what they were talking about. Hit me up with a reply. Sorry such a long type. D
     
  15. One reason I went with the Fender Super Bassman. It has a 8, 4, and 2 ohm selector for impedances. I myself wouldn't mix the impedances if the Amped says no, or doesn't advise it.
     
  16. JJR58

    JJR58 "Big Angry Piano" Supporting Member

    Dec 2, 2010
    Queens NY
    Listen to Ampeg and Jimmy.
     
  17. D Rock 247

    D Rock 247

    Dec 24, 2016
    Thats the bad thing about what happend. It actually sais to put a 8ohm cab to a 4ohm load.....but ill be danged if thats not the third or fourth time ive heard someone mention owning a fender bassman. I might just have to bite the bullet and sell my mesa and get one. Does the bassman get dirty though? Not too dirty, just a little grind whenever i start banging the crap out of those bass strings.
     
    gsgbass likes this.
  18. D Rock 247

    D Rock 247

    Dec 24, 2016
    8 ohm cab to 4 ohm load at half power. I just dont think the amp can handle it. I could just have a bad apple. Who knows
     
    gsgbass likes this.
  19. Use the Overdrive Channel on it. I'm liking the Vintage Channel too much.
     
  20. The SB puts out 300 watts, no matter what impedance it's set on.