1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
     
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

8 ohm head into a 4 ohm cab. How bad?

Discussion in 'Amps and Cabs [BG]' started by snoopz, Apr 14, 2009.


  1. snoopz

    snoopz

    Mar 16, 2009
    SF, CA
    Just lucked into a Traynor YBA-1A Mk II. Consensus seems to be that it puts out somewhere between 45 and 90 tube watts at 8 ohms.
    So, if I plug it into my Ampeg SVT 410-HLF (4 ohms, I think can handle 400 watts), am I going to overheat and destroy my cab? Or will I be ok? Just wanted to get some opinions before I give it a try.
     
  2. RickenBoogie

    RickenBoogie

    Jul 22, 2007
    Dallas, TX
    I'd check to be sure the AMP can handle a 4 ohm load. You're not going to hurt the speakers, but tube amps MUST be matched to the load they were designed for.
     
  3. MIJ-VI

    MIJ-VI Banned Supporting Member

    Jan 12, 2009
    Hi snoopz.

    Your 90 watt YBA-1A Bass Master Mark II needs an 8 ohm load.

    That being said, Music City (a music shop in North Bay, Ontario, Canada) routinely rented the YBA-1A Mk II (and other Traynor tube heads) matched with the YC-610 cab (6X10", 5.3 ohms) to bass players all the time.

    But I wouldn't be comfortable running any tube amp at half (or double) its speaker impedance rating.

    --------
    Tube amp tips & Traynor amp schematics: Viva Analog

    More: Velvet Black
     
  4. Your cab will be fine. It's just a passive device presenting an impedance.

    Your amp will be less happy with having an incorrect load attached, and it may be damaged.
    Since it is tube, and not solid state, I would feel ok plugging it in and trying it, briefly, at low volume.

    If after that you really like it, you could get an 8 ohm cab, or get a second 4 ohm cab and a special series speaker cable to run an 8 ohm load (normally two 4ohm loads is equal to 2 ohms).
     
  5. I still wonder how 90 watts ever came our of a 50W max dissipation pair of tubes...

    I wonder how the new production would fair in that amp? I guess they came with Mullards from the factory which might explain something. But still...
     
  6. blockinlay

    blockinlay

    Feb 21, 2009
    Phila Pa
    Won't hurt the cab, but you might fry the amp. Tube failure and output transformer damage. The speaker is part of the amp circuit. Using the wrong ohm cab causes an imbalance. Probably be a slow fry.
     
  7. cripula

    cripula

    Dec 20, 2006
    Canada
    Personally I wouldn't. The YBA-1A is a wonderful amp! Get yourself a nice 8 ohm cab for it and be happy.

    Mine sounds awesome through a Bag End S15-D or Bergantino HT112ER. Love it.
     
  8. Jonesy

    Jonesy

    Feb 21, 2006
    +1. It's a great amp. Tubes will last 3-5 times longer with an 8 ohm cab vs a 4 ohm.
     
  9. They REALLY overstress those bottles! Another good reason to not mis-match speaker impedance :bassist:
     

Share This Page