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I have joined the Dark Side (well not really)

Discussion in 'Amps and Cabs [BG]' started by Psycho Bass Guy, Dec 11, 2007.

  1. mgmadian


    Feb 4, 2002
    Austin, TX
    Lookin forward to hearing how your thoughts and experience with the tube swaps. Also any other changes or mods to the 400+.

    One random thought I've kicked around: since I never use the effects loop on my 400+, I'm wondering if (i) it's feasible to either bypass the parallel loop completely, or change it to serial, and (ii) if there'd be any benefit to doing this.

    My crude thinking is that (generally) less circuitry in the path is better, and since I never use the effects loop (which AFAIK since it's parallel, means it's always at least partly in the signal path, even when dialed-down... that right?), so it's expendable... or something like that.

    Then again... it's an amp that sounds good as-is... why mess wit it? :p
  2. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    I take it you were not impressed? Or just wanting to play around a bit?

  3. There's some funky upper midrange thing going on that I don't like. I love the preamp's flexibility, but I tried the Boogie out using a new Vietnampeg 810e and that cab couldn't reproduce that funky tone or handle any serious volume, so I didn't hear it then. I checked it on a GK cab just long enough to make sure it was the Ampeg cab barking and not the amp, and it was the cab. I DID like the tone of through 810e before breakup; I just didn't realize how much of the amp I wasn't hearing. At home I'm running it through a Music Man HD212 and an old Trace Elliot 1153. The Trace is merciless with mids; it's a Trace.
  4. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    Man, I love both of those cabs! Great call. :cool:
  5. You guys mentioned TE...can you describe the mid-range sound you are writing about?

    Also, if you've heard the new generation of Trace Elliots, what do you think of the Gibson/Peavey generation TE's?

    Should I start a new thread?
  6. What specifically do you want to know?

    They're very similar to the old stuff. I like them.

    Please do. It will be a nice change from all the Markbass threads.
  7. Curious. Do you mean that using the MV. Is the MV a linear taper pot?
  8. coyoteboy

    coyoteboy easy there, Ned Supporting Member

    Mar 29, 2000
    Sactomato, CA
    when I think of amps getting lost in the mix, the 400+ is the absolute LAST amp on that list. The best rock tone I think I ever heard on stage was the 400+ through 2 2x15 cabs. It took over the show.
  9. No. I was using a little hyperbole to illustrate how my amp was very "gainy." I've heard other people talk about how clean their Bass 400+'s are, but mine wasn't at all until I did some tube swapping.

    The problem was the JJ preamp tubes. They were the source of the weird upper mids and excessive gain, along with a tone circuit that I have decided is too bright in stock form. All the other JJ 12AX7's I have already were very neutral sounding with almost slightly muted mids and highs. These are bright and thin in the amp, almost like old Chinese 12AX7's.

    Just to give folks an idea of the tone I was looking for, I was trying to get the amp to sound like the late Bobby Sheehan of Blues Traveller. He used a 400+ with a Jazz Bass and got a very nice tone. I especially like how the G string has presence but isn't brash. I don't like thin-sounding D and G strings.
  10. Oh, okay. Gotcha. ;)

    I'm also curious about the JJs. Were they current production? IOW, currently they make their ECC83, and their so-called ECC803.
    I'm wondering if either of those are what you mention, or perhaps some older JJs that might not be the same as what's showing up these days.
  11. anderbass


    Dec 20, 2005
    Phoenix. Az.
    I feel the exact same way about my (fully-JJ equipped) 400+ too.
    You've given me new-found hope for mine and I'll give some different preamp tubes a shot.

    My 400+ is currently (or will very soon) be undergoing an adjustable bias mod by my amp-tech.
    Do you have any thoughts or technical advice I could pass along to him on this subject?

  12. I had that thought as well, that they might be the "high gain" ECC803's, but they're not. I'm guess that it's just production variation.


    I don't think the problem is necessarily just the JJ's. I think it's a combination of the amp's voicing and the tubes' inherent tone. I remember theorizing a long time ago that Mesa voiced its amps around the cheap Chinese 12AX7's they sold. I have bunch of Ruby 12AX7s from 10-15 years ago, the same ones that Mesa used to sell, so I put a full set of them in the amp. I was right The amp's preamp was nothing like it was with the JJ's. It was a little noisier, but the tone knobs became much more responsive, and even with a 12AX7 as a driver, the amp was much cleaner than it had been with the JJ preamp tubes. What's really funny is that those same Chinese 12AX7's are icepick treble machines in every other amp I've tried them in, but in the Mesa, they sound like RCA's in a Fender, just noisier. It's funny that JJ's are dark in other amps but too bright in the Mesa and that the Chinese 12AX7's that are too bright in other amps sound smooth in it. A plus is that those Chinese tubes are very cheap and abundant.
  13. Chef

    Chef Moderator Staff Member Supporting Member

    May 23, 2004
    Columbia MO
    Staff Reviewer; Bass Gear Magazine
  14. mikeswals

    mikeswals Supporting Member

    Nov 18, 2002
    Seattle / Tacoma
    I thought the JJ preamp tubes sounded just fine in both my old 400's.

    I have a box full of the Sovtek 12ax7 I really didn care for....
  15. The 400+ may be voiced differently. I don't have schematics for either, but I do know that the 400+ resulted from Mesa not being able to get good US made tubes anymore, hence the twelve 6L6's instead of six 6550's. It's possible the preamp was re-voiced as well.
  16. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    You read my statement out of context. I wasn't saying the 400+ is on my list of "amps that get lost in the mix". Knowing that Psycho is an avid SVT user like myself, I was curious as to whether he thinks the 400+ gets lost in the mix *as compared to an SVT*. IMO, an SVT has the 'cuts-through-concrete' midrange that the 400+ does not. Don't get me wrong, I like the 400+, it's just not my sound.
  17. Have you messed with the power tubes at all (maybe putting some Chinese ones in there too?). On my (JJ loaded) 400+, the knobs don't make much of a difference unless you turn them pretty much to their limits (especially the mid knob) but the push-pull of the pots all make huge differences and the graphic EQ seems to make a big difference as well. Can you recommend some modern preamp tubes that may be good to experiment with?
  18. No, the power section sounds great. When I run the bass straight into the effect return jack, I really like the tone, it's just not loud enough. IIRC you're running multiple taps off your OT simultaneously, in which case the lower secondary impedance is being reflected back into the primary and loading down the whole amp, tone controls and all. If you use just one cab, do your tone knobs work better?
  19. anderbass


    Dec 20, 2005
    Phoenix. Az.
    I took Psycho's advice and just got my 400+ back from my tech (fellow T/B member timv) yesterday.

    Tim instaled an adjustable bias mod, two Chinese 12AX7's he'd tested/selected out of my stash of used spares (1 Groove tube 12AX7 and a Mesa STR SPAX7A), and then instaled a (quote) well balanced 12AX7 in the 3rd slot (JJ), and a well balanced 12AU7 in the 4th or left position. (older used tube that only seems to be labeled "USA 12AU7A")

    (I believe I'm quoting my tech correctly here)
    He stated that after the bias mod, my amp still only maxed out at around 270 watts (clean) due to its transformers limited capacity, but each side of its power section was now much better balanced and showed much less crossover distortion . He tested and found a surprisingly large variation in my two year old set of (Matched) JJ power tubes and arranged them into 2 groups of the closest matching sets, while exchanging one that tested much lower with a better matching JJ he had in stock. He also cleaned and tightened all my power tube socket conectors to better fit my JJ's power tubes somewhat smaller than normal sized pins. (I think I read somewhere that the newer JJ's power tubes now come with normal sized pins)

    When I picked it up, he didn't really expect me to notice a huge improvement, but I definitely do.

    Previously, my (fully) JJ equipped 400+ has always had me constantly knob twiddling in a futile attempt to tame its somewhat harsh upper-mids while trying to compensate for the comparatively thin sound I got while playing upper register notes with my basses.

    The tone now is very rich, full and much more three dimensional sounding at nearly any imaginable knob settings compared to before. The upper register notes now ring out full and much thicker sounding, the harsh upper-mids are completely gone and the lows are allot tighter. It simply sounds better in every way.
    I know the real test will be with my band. I've only spent a while trying out different combinations of preamp channels, tone knob and push-pull settings, but I honestly cant make this thing sound bad now, no mater how I set it.
    Psycho already stated this, and I completely agree that my tone knobs are absolutely much more responsive with this different tube arrangement compared to my previous JJ's.
    My Mesa seems to be a plug and play amp now, and I've always considered it to be anything but...
    I'd highly recommend the bias mod and a similar tube arrangement to anyone not completely satisfied with their 400+.

    The small panel in the center is the adjustable-bias pot board he built and instaled to a previously-existing mounting hole. (looks like its always been there)


    I'd like to thank both Psycho for his tips/PM's and especially timv for the wonderful job he did on my amp.
  20. pedro


    Apr 5, 2000
    Madison, WI.
    Cool. That PBG, is a smart cookie.

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