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New MESA 400 owner here, any help vets?

Discussion in 'Amps and Cabs [BG]' started by kosmicwizard, Nov 15, 2010.

  1. I just got a MESA BASS 400 (non +) in the mail, it doesn't have a owners manual and MESA's website doesn't have it there either. Do any of you have an online version of it you would be willing to share with me?

    That might be the solution to my question, but I will ask it anyway. With it having 4 outputs on the back of the amp (2 4 Ohms and 2 8 Ohms) does that mean that I can attach a cab to any and or all of them?

    Most tube amps have a selector to tell the head what the Ohm draw is going to be, I can't see one on my MESA, and I want to be safe. I have it hooked up to a Ampeg 8X10E right now (with one cord from the 4 Ohm to a mono input on the back of the cab) can I plug in a Ampeg 2X15E into the other 4 Ohm connection, for a total of a 2 ohm load?

    Or do I need to connect the cabs in series and then plug the two of them connected together into an 8 Ohm connection? I want to leave them as is if possible, but I don't want to damage my head if I can help it. Thanks all in advance. Cheers.
  2. The 400 is intended for 4 or 8 Ohm loads. While some have reported running a 400 at 2 Ohms for a very long time with no difficulties, it's your choice if you want to try it. You would use 2 8 Ohm cabs, one plugged into each "4 Ohm" jack, for a total of 4 Ohms. One 4 Ohm cab plugged into one of the 4 Ohm jacks is also fine. Similarly, 2 16 Ohm cabs, 1 in each of the 8 Ohm jacks, would make an 8 Ohm load. If using 1 8 Ohm cab, plug it into one 8 Ohm jack.

    Try to think of the 4 Ohm jacks as, "4 Ohm total load;" 4 Ohms on one or a total of 4 on both. Similarly, 8 for the 8 Ohm jacks. If you are concerned about varying from the manufacturer's specified load, wire your 2 cabs an an 8 Ohm load and plug into one 8 Ohm jack, like you were thinking.

    Download the 400+ manual from the Mesa website. Much of it still applies; all the controls on the front of the amp are the same, and the only difference in the back is that the 400 does not have 2 Ohm load jacks where the 400+ does. Physically you have less tubes, but the 400 has the ability to take either 6L6 or 6550 tubes - though it's advisable to have a tech make the change in tube types as a bias adjustment may be needed.

    With 6550 tubes I noticed a very slight increase in perceived volume, a slightly more full, bassier sound, and most noticeably an increase in headroom. With 6L6 tubes my 400 distorted at lower volumes, but it was a great sounding distortion. I preferred it to the 400+ for this flexibility.
  3. Thank you. So should I listen to the people that have reported running this amp on 2 Ohms and never having a problem? Or does anyone want to sell me a series cable? My local music store doesn't have any. Cheers.
  4. Anyone?
  5. Nightlyraider


    Sep 30, 2009
    I don't follow with this "total load" thing. The different taps are from different places in the winding. But wouldn't you daisy chain two 8ohm cabs and plug that into a single 4 ohm input? Or else you could plug each of the cabs into an 8 ohm output?

    I didn't think the output taps were effected by using one of two of them.
  6. Since MESA didn't have user manuals for the 400. I read about the 400+, the Buster and the D-180. On the Buster it says "BUSTER incorporates two sets of speaker output jacks for use with different cabinet set-ups and between them
    most impedance loads can be accommodated. Two 8 ohm, and two 4 ohm outputs are provided for matching different or additional
    cabinets. The 8 ohm outputs should be used with the BUSTER combo as the two custom designed Electro-Voice Basis 16 ohm - 10"
    speakers are wired in parallel, producing a total impedance load of 8 ohms. If you have chosen
    the Head version of BUSTER, you will likely find yourself using different impedance loads from
    time to time. Here are some of the more common scenarios for a proper impedance match;

    4 OHM 8 OHM
    * 1 x 4 ohm cab - use 4 ohm output
    * 2 x 8 ohm cabs - use the two 4 ohm outputs
    * 2 x 16 ohm cabs - use the two 8 ohm outputs
    * 1 x 16 ohm cab + 1 x 8 ohm cab - use 16 ohm cab
    in 8 ohm output and 8 ohm cab in 4 ohm output

    Although it is possible to use 2 x 4 ohm cabinets with BUSTER by connecting each of them to the 4 ohm outputs, power will be
    reduced and the bold authority present with the proper impedance match will be compromised. This mismatch will also put excessive
    loading on the transformer which will produce additional heat, thus tube life may be shortened. If you must use the BUSTER with two
    4 ohm cabinets, it would be wise to combine them in series in an external box or connector and then connect that combined 8 ohm
    load to one of the 8 ohm outputs on BUSTER."

    Not sure that all of this exactly applies, but if nothing else it is good to see what MESA had in their heads at the time of manufacture. Cheers.
  7. Nightlyraider


    Sep 30, 2009
    Good to know, thanks a bunch!
  8. Yarslv


    May 18, 2009
    I think it's logical: if MESA uses the same "strategy" for BUSTER, and 400+ it will work for 400 too.
    Principal scheme of 400 and 400+ may be considered as identical. The only exception is a set of tubes.
  9. Correct.

    Most of this should apply to the 400 as well, since its speaker outs are configured like the Buster. I recall that the 400+ manual said a "slight mismatch" was safe, or something to that effect, sounds like similar wording to the Buster section above. If the 2 Ohms bit applies to the 400, it sounds like even if safe you might be losing more than you would stand to gain by adding the 2nd cabinet.

    My own experience is limited to 1 hour at a 2 Ohm load. Sounded fine to me, but I was worried about the possible effects of prolonged use at 2 Ohms so I stopped. Maybe I worried needlessly.

    I searched TB for the name of one guy I remembered saying he ran his 400 at 2 Ohms, and came up with this post:

    Make of it what you will. Might be worth calling Mesa and seeing if they still have anybody there who remembers the old 400 amp.
  10. Thank you so much for the help guys. Could this be one of those times when the engineers designed it to be able to do more than they say it can and yet they stick to what they have said so that if things go terribly wrong they don't have to repair the head under warranty? Since this head hasn't been under warranty for a long time, I don't have any reason not to try this out. If it doesn't sound good to me, or if I get afraid, I may get a series cable and see if that is still as loud. It is not like this is a SS that produces more watts with less Ohms or anything. Another thing I have been thinking about, and please let me know if my logic is flawed in some way, since this amp can accommodate 6550's (which have more headroom and break up later) If I have them in it running colder than 6L6's and am running a 2 Ohm load things will be all good in theory right? Also, what is this have your MESA changed so it can be biased all about? Didn't MESA intentionally build their amps without bias to stop techs from juicing customers with all the biasing holiballu? Or is this MESA propaganda that I bought due to my naivety? Cheers.
  11. Yarslv


    May 18, 2009
    Well, I can see your logic but tubes are not the case. It's mesa's output transformer. This is the thing that sets output impedance. As the manual says: there wont be major non conformity, but that may shorten a tube life.
  12. anderbass


    Dec 20, 2005
    Phoenix. Az.
    I think part of that biasing holiballu was so Mesa could sell you a brand new 'matched' set of their recommended overpriced, re-branded power tubes.

    But once you have an adjustable bias mod done an amp tech could easily re-adjust it to better match the old powertubes that had simply drifted a bit, or to safely use most any other brand of new replacements you like.
  13. got ya, thanks anderbass and yarslv!
  14. All I have to say is... you're running an 810 and a 215? That's seriously loud!!!

    You're a god.
  15. It is very loud. I am not a god, but I am trying to be a good person. Thanks for you opinion. Cheers.
  16. twinfallsbass

    twinfallsbass Supporting Member

    Jan 24, 2005
    Somewhere in AZ
    I used to have a Mesa 400. I played it @ 2ohms frequently and even played a four hour set no problem.
  17. Thank you for letting me know! I am much more comfortable now. Cheers.
  18. So I got the Bass 400 manual from a great Tb'er who took the time out and scanned it for me. This is what it says in the section about "Speaker Jacks"


    Two 4 Ohm and two 8 ohm jacks are provided. Unlike transistor amplifiers, the Bass 400 will provide full power at both 4 and 8 Ohms. Furthermore, speaker impedance mis-matching is not critical and perceived loss of power will be minimal. When using more than one speaker cabinet, remember that the total load impedance goes down as more cabinets are hooked up. For example, if you use one 8 Ohm cabinet, use one of the 8 Ohm speaker jacks. But if you use two 8 Ohm speaker cabinets, they will be operating in parallel and the total load will be 4 Ohms. Therefore, plug each cabinet into a 4 Ohm jack.

    If you want to use two 2X15 cabinets were each individual speaker is rated at 8 Ohms, the best results will be achieved by wiring the speakers inside each box in series. Then each cabinet will become 16 Ohms and each cabinet should be plugged into an 8 Ohm jacks. But if this seems too complex, do not despair! Some of the heaviest players of the Bass 400 (Michael Anthony, Juan Crocier) use pairs of our standard wired 2x15 cabs, each plugged into a 4 Ohm jack."

    So I just want to clarify, a standard wired Mesa/Boogie 2X15 back then had a total load of 4 Ohm per cabinet correct? So I see no difference between a 4 Ohm 2X15 and a 4 Ohm 8X10 ... Does anyone else? I hope this helps someone else at some point in the future. Cheers.
  19. This isn't exactly thread related, but if anyone in the future is using this to see Ohm capabilities of older MESA/Boogie products I have one more at present from the Mesa Strategy 400 all tube poweramp.

    Under the section entitled Output it reads:

    "Each channel of the Strategy 400 offers two 8 ohm plus two 4 ohm quarter inch jacks for connection to speaker cabinets. Unlike transistor amps, the 400 will produce full power at either 4 or 8 ohms, and mismatching of speaker impedance will not cause damage or severe loss of power (extreme mismatches will decrease tube life however). Avoid running either channel without a proper load or damage may result. When using more than one speaker cabinet on a single channel, remember that the total impedance goes down as more cabinets are hooked up. For example, if you use one 8 ohm cabinet, use one of the 8 ohm jacks. But if you use two 8 ohm cabinets on the same channel, they will be operating in parallel and the total load will be 4 ohms. Therefore plug each cabinet into a 4 ohm jack."
  20. Thanks for adding this info. I'm sure sometime in the future someone will be happy you did. It's irritating to be the guy searching for an answer but find only threads full of unanswered questions from several years ago.

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