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8 ohm issue, PLEASE HELP! tech 'geek' needed

Discussion in 'Amps and Cabs [BG]' started by bass_stylee, Oct 25, 2006.


  1. ok, so i picked up an all tube 200watt fender studio bass power amp from a friend for next to nothing. it's got great tone with some slight growl and i've loved it for 3 years. never had any issues other than replacing the 2 of the 6 tubes as they had begun to put out less. i'm now in the market for a new cab rig so i take my head into some guitar shops to test out different cabs and see how they sound with my head.

    here's the issue. my head was probably pulled from a 1x15 combo that fender made and it appears that it is only wired for an 8 ohm load. meaning that i'd have to get an 8 ohm cabinent to compliment it.

    my needs. i need more than just a 1x15 and more than just a 4x10, though these would be great in combination, i know that i cannot just chain them together either. i need volume, warm vintage sound, and i have a low budget. my max to work with right now is a brand new 1x15 ampeg cab i could barter and an addtional $300-$500. most all cabs that would fit my needs run at 4 ohms!

    i've been contemplating building a cab, cost efficient and could work. just not sure if i could wire it at 8 ohms, plus i would need some help as i am only versed in the carpentry side of this solution. i'm wondering if a 4ohm cab could be easily rewired for 8ohms, or if that would just be crazy talk.

    please help! i'd like to keep this power amp as i've grown attached to it. thanks!
     
  2. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    There is no way possible to rewire a 4 ohm cab to 8 ohms. I recommend you read the ohms/impedance FAQ stickied to the top of the forum so that you understand how to wire your cabs if you decide to build.
     
  3. you could get two 4 Ohm cabinets and have a special cable made that wires the two in series. it's not hard. i'm sure you could get a cable manufacturer like bayou cables to make one for you.

    robb.
     
  4. wait. aren't there different ways to wire the speakers in a cab which can change to the ohm rating of the it? i mean, there clearly isn't only one way to wire the speakers in cab. so why couldn't i just rewire the speakers if they were rated at 8ohms? for instance. ampeg makes a classic 410 and a 410hlf. each contains the same speakers, but the hlf is ported and tuned differently. so are you saying that it would not be possible to wire the 410hlf like the regular 410?
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Yes, but 4 ohms and 8 ohms from the same cab is not possible. 4 ohm and 8 ohm 4x10s are usually accomplished by using 4 ohm and 8 ohm drivers, respectively, with the odd cab using 16 and 32 ohm drivers to accomplish the same.
     
  6. this is not to mention that it would be considerably easier to get a special cable to wire two cabinets in series than it would be to try to rewire two cabinets internally. seriously, look into it. you get what you want in every respect.

    robb.
     
  7. money my friend. maybe you skipped that part. i can't afford two cabs right now. trying to accomplish this on a budget is quite a difficulty. consider. i have a 1x15 cab at 8 ohms and about $300. i just don't think that i can afford what you are proposing. in addition, i need to be heard in practice and on stage. i do like your suggestion for down the road, would love to chain two cabs together in a series. but it's just not practical for me now. any other suggestions?
     
  8. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I rebuilt a Studio Bass 200 for a buddy of mine (hillbillyfunk on TB). His situation was exactly the same as yours. He ended up getting an 8 ohm 4 X 10. He blew his 8 ohm 1 X 15 Avatar almost as soon as he got it. It wasn't really quite loud enough anyway, I think. Get what you can afford for now, selling your 8 ohm cab so you can afford something nice.
     
  9. any suggestions on a ported 4x10 that runs at 8 ohms? i need the extra lows because i play a 5 string. all of the non-ported 4x10 cabs i've played have nice punch, but no nuts (bottom end) to support it. thanks.
     
  10. like passinwind says, you could sell your 115 and get two used cabs that will work well and fit the budget. craigslist is magical for that sort of dealing. i honestly don't see any other option, since your 8 Ohm cabinet is a single driver. there is no way to rewire it for a different impedance. the reality is you'll have to ditch your 8 Ohm 115 if you want to use another cabinet. there is no other way for this to work.

    robb.

    robb.
     
  11. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Los Angeles, CA
    Correct me if I'm wrong, but my understanding is that tube amps can be run safely at speaker loads below their rating....I know that a previous engineer for Ampeg (I think its Ampeg) would take their old 1x15" cabs that originally had an 8 ohm speaker and load them with 4 ohm speakers- it does change the sound though, which is why he did it I think- the Ampegs were originally designed for jazz musicians and he wanted something that would be dirtier for the rock musicians. I've heard elsewhere that this is safe to a degree with a tube amp, but not with a solid state amp of course....
    Don't quote my on any of this, as I am no "tech geek"- but I figure its worth looking into for your situation.
    Karl
     
  12. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Try PM'ing hillbillyfunk, he looked into all the options pretty hard I think. I believe his 4-10 is sealed though, which he prefers. His amp really made the woofers in my ported cabs dance when I was trying the amp out, and I only use 4-stringers.
     
  13. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    The downside is that then you have an 85 pound (well, really heavy anyway), ~100watt tube amp head!
     
  14. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I'd fnd out for sure about that. Tube amps have wide latitude with the loads that they'll safely handle. 4 to 16 ohms isn't unusual. In college when I didn't know any better I used a Fender Showman as a PA head with 2 ohm loads full tilt and never had a problem with it.
     
  15. enim

    enim

    Jun 29, 2006
    Chicago, Illinois
    i would think that as long as you watched the heat, it would be fine at 2 ohms. or 4.
     
  16. just found out that eden has a 410xlt that'll run at 4 or 8 ohms. very excited. thanks for all your input.
     
  17. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I was a Fender warranty tech when that amp came out. They are fragile and were not in production for very long at all. It wants an 8 ohm load, period. I've tested this on my bench, I'm not speculating. The plate voltage is a bit higher than most Fenders, and a 16 ohm load would be a very bad idea. Running lower than the rated load probably won't hurt the amp, but the resultant power loss negates the whole reason for owning it, IMHO.

    Lots of Fender tube amps will tolerate 100% impedance mismatches, upward or downward. The Studio Bass 200 is not one of those.
     
  18. slyslam

    slyslam

    Aug 23, 2006
    Do you know if the output transformer has a multitap configuration for several impedance? I might be wrong but you could probably make a 4 ohms impedance if available.
     
  19. Ben B

    Ben B

    Jul 13, 2006
    San Diego, CA
    Bass_stylee's information is correct. The Studio Bass had only one output jack and was labeled only for 8 ohms. There was no output impedance selector. It came with a 1 foot long cable to connect it to the internal speaker. It appears that Fender did not design it to run with a second speaker. I guess that's why it's a "studio bass" not a "concert amp".

    I ran one for a few years using both the internal speaker and a 1x15 8-ohm cabinet. The amp ran hotter with the 4 ohm load than it did with 8, but it never had any problems. And it was very loud!

    My amp was fairly new at the time. Bass_stylee's must be at least 20 years old, so, running it hotter might cause something to fail--perhaps output tubes???.

    Ben
     
  20. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    It doesn't, unfortunately. Lots of Fenders don't. I looked into aftermarket output transformers, but that's a fairly expensive proposition.
     

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