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Will a 400+ do 6 ohms?

Discussion in 'Amps and Cabs [BG]' started by thirdeye, May 9, 2003.


  1. If I hook a 6 ohm cab up to the 8 ohm output,would I get less or more power than a matching 8 ohm hookup?


    thanks:cool:
     
  2. Mike

    Mike

    Sep 7, 2000
    Cali
    Shpuld get a lil' more, in theory.
     
  3. You're talking about a Mesa 400+? From what I've read from the "tube heads" when you mismatch down as you are proposing, you run little risk of damage but you do loose a little power.
     
  4. Bluesbob

    Bluesbob

    Mar 13, 2000
    Springfield, TN
    A tube output stage should be stable into eight or four ohms as long as the correct tap (or output jack) is used. In other words it will put out 400 watts max @ a certain frequency into 8 ohms (from the 8 ohm tap) and 400 watts max @ the same frequency into a 4 ohm load (from the 4 ohm tap). 6 ohms is right in the middle so you could use either output tap of the tranny and get the same (theoretically slightly less than) 400 watts. This is different than a solid-state amp which, if perfect, would double in power as the impedance is halved. None of them are perfect though, which is why you don't see that 2:1 ratio anywhere but in high-priced audio.
     
  5. hehe.:cool:


    Where I'm from,it's hard for me to get definite answers to odd questions like this one from anywhere other than this place,even Mesa is hard to contact.

    So to get as many opinions/facts as possible I thought starting another thread would round up some more "tech heads" to help me not blow up my precious tube amp.

    Thanks for your help. :)
     
  6. There's a HUGE problem with your looking for a number of different answers. Amp operation is NOT a matter of opinion. The laws of physics don't take polls and very little popular thought is factual concerning tube amps. Just because someone feels like commenting on something doesn't mean they are qualified to render technical advice. Not be a pain, but the answer I have given you IS the correct one and if you don't believe what I've said, I'm sorry. Chances are you won't destroy your amp, but improper operation is NOT good for it. Go lower than the tap, NOT higher.
     
  7. Hey man,don't take it personally.

    I'm sure you wouldn't take any of my advice as fact until you knew me a bit better.I'm just getting a feel for the people around here.

    All your posts do seem well thought out and intelligent,but for a guy like me that doesn't know alot of tech,I've gotta take everything with a grain of salt to start with,and once I see more people are telling me the same thing I'll build a trust for your or anyone elses information.

    As far as I know you could be a Psycho.

    Please take that last one as a joke :( :cool:
     
  8. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Ok, then. In light of this, I am not going to share my feelings on this matter.
     
  9. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Well, I guess you wouldn't know me either, but if I ever have a problem of any sort, or even a simple question about tube amps, you can bet your ass I'll be coming to this board and PMing Psycho Bass Guy. He's got more experience than damn near all of us, and quite frankly, knows his s***. I've never met the guy, but I trust him as much as...hell...more than any tech I've ever met. Solid state and tube amps are two totally different beasts. PBG is pretty much THE tube amp guy around here (I'm sure there are others, but they seem to always agree with facts like these, so they don't make redundant posts), so do yourself a favor and don't go with whatever you hear most of. With a tube amp, chances are it's totally wrong. Hey, it's your cash... Later---
     
  10. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    Munji, you're so cuuuuuute......
     
  11. Thanks:) ,

    I just learnt more about Psycho quicker than if this thread didn't turn out so defensive...........maybe this turn of events was a good way to find "THE tube amp guy".

    I hope Psycho will help with any future questions I may have.
    This place is a wealth of information.

    Cheers
     
  12. Bluesbob

    Bluesbob

    Mar 13, 2000
    Springfield, TN
    You asked if you would harm your amp by hooking a six ohm load to the 8-ohm output. The answer is "no it won't harm the amp". Connecting to the 4-ohm output may be better sounding, try both. I have an '89 SVT II which has only 4-ohm and 2-ohm output jacks. I wanted to use my 8-ohm Goliath III. I called and e-mailed Ampeg and e-mailed people at the unofficial ampeg web-site and it was unanimous, "no it won't harm the amp". We had a steady outdoor gig every Friday last summer, by the water, in the sun. I put a lot of miles on my new Sovtek 6550's without a whimper. In fact the tubes may have been taking less of a beating. I realize the issue is the output transformer, but I doubt the SVT is that much more robust than the Mesa. Of course, I don't abuse the amp or any of my equipment.
     
  13. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Then there's the Bob Lee camp. Of course, you could always ask them both (nyuk nyuk nyuk).
     
  14. The problem with this analogy is related to the tube types and not the amp manufacturers. The Ampeg's 6550's have half the output impedance of the Mesa's 6L6's. That mean it's easier for plate voltage to rise with 6L6's from a transformer mismatch.

    Even though the Mesa's twelve 6L6's have a combines output impedance equal to the Ampeg's six 6550's, an inductive voltage spike will do more damage to the tubes "nearest" the output tranny. A 6550 also has a much higher plate current disappation rating, meaning that any inductive peaks can be "absorbed" more easily so with 6550's a higher impedance is less dangerous.

    As I have said earlier, most amps can tolerate a 100% mismatch either way, but it is better for the amp and the tubes to go lower.

    BTW, just to piss Munji off, my Eden VT300 may sound great, but it is a layout nightmare, put together like a Behringer. :spit:
     
  15. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Don't know much about the VT300 ... or any other tube amp, either. I think they blow, in general. Besides, isn't that amp made by Koch?
     
  16. ChenNuts44

    ChenNuts44

    Nov 18, 2001
    Davenport, IA
    (nyuk nyuk nyuk).

    :D
     
  17. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    NOW who's cute?