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Mesa D180/400 Tube Question

Discussion in 'Amps and Cabs [BG]' started by stevekim, Mar 20, 2003.


  1. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    I've got a Mesa D180, the earlier 200 watt version of the 400 with six 6L6's. I've been talking to Mesa about replacing the 6L6's with 6550 to get more power. They haven't exactly been the most helpful on the matter but they tell me that it IS possible to use 6550's with my D180. The main issue would be to find tubes that will actually fit inside the chassis, many 6550's will be too big.

    Anyone try 6550's in their mesa D180 or 400? Did it require modification of the power supply? I would really appreciate any help on this.

    Thanks,

    Steve
     
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Don't have one but I'm sure that the bias would need to be changed. Also, I'm not sure how much current a 6550's heater draws in comparision to a 6L6...something else to check.

    Not sure what kind of load impedance the 6550s like either, or plate current...my tube manual is at home.

    Do you really need more power? Would it be worth dropping that much coin on a sextet of 6550s and mods to your amp for a little more power (the output tranny can only handle so much).

    What would it cost you to sell the D180 and buy a 400 or 400+? I don't know, just writing my thoughts.
     
  3. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    i would make sure that the 6550's are within the bias ranges for my particular amp, that way i won't have to make major modifications to my amp. i don't need a whole lot more power. the 200 watts from my D180 and two 1x15's *is* loud enough for the VERY loud rock band i play with but i wouldn't mind a little more. :)

    i've thought about selling my d180 and getting a 400 or 400+. the sheer amount of tubes that are in the 400+ scare me. i would much rather stick with the 6 tube format of the D180 and 400. i supposed i can get a used 400, but if i can up power rating on this thing without having to go through the hassle of selling this amp and looking for a new one i would rather do that.

    i've been in communication with the people at thetubestore.com who have been extremely helpful. they want me to measure the amount of space inside chassis so they can pick the right tube for my amp. we'll see how that goes.

    i guess my question is, how much extra power can i realistically expect from this tube change? assuming i don't make any modifications to the power section.

    steve
     
  4. 6550s aren't direct substitutes for 6L6s so you will need to mod the amp; at least a bias circuit mod, probably more. 6550s are designed to operate at higher voltages and draw more current than 6L6s so I doubt the power supply would be up to it. Unless you up the plate voltage on the tubes you won't get any more power anyway, that's ultimately limited by the power supply. I don't think the return would be worth the effort.
     
  5. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    you know, that makes a lot of sense to me but when i talked to mesa boogie they made no mention of any of that. that is why i'm beginning to wonder about the advice they've been giving me.
     
  6. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    6550's may increase the wattage a little bit (maybe 30-50 watts), which hardly seems worth modifying your amp for such little return. Not to mention that 6550's are nolonger being produced; all the remaining supplies are NOS, and once those are gone, you'll have to convert the amp back to 6l6 specs. Try Mesa's STR454 tubes. They are 6l6's, but they operate more efficiently and have more headroom and lowend. If that isn't enough I'll gladly buy your D-180.:D
     
  7. They won't increase the power at all unless you mod the power supply, and 6550s are still currently being produced. You must be thinking of another type....
    Properly powered and biased 6550s can generally produce twice (or more) as much power as 6L6s.
     
  8. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Actually, they are not being produced anymore (unless some factory just started up recently). I went to the Ampeg factory last year for training for a music store where I work, and Ampeg was showing off thier new 300 watt Crate head, which ran on 6550's. Ampeg bought all of the remaining supply of GE's 6550 tubes, which was enough to make about 100 amps. They said that they would have to make them with 6l6's once those ran out, as nobody was making them anymore. If you know otherwise, please tell us who is making them so we can retro fit all those SVT's!!

    And yeah, you would have to mod the power supply as well. Good observation there. All the more reason to sell the D-180 to me! Haha!:D :D :D
     
  9. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    don't worry, basstriaxis. i'm not not about to do anything extreme to my d180. i love this amp, i just want it to be the best it could be.

    the interesting thing about this is that the original bass 400 came equiped with 6550's but then switched to 6L6's. this happened before they came out with the 400+ which runs on 6L6's. so you've got some older bass 400's with 6550's and some with 6L6's. the reason i think it might not be a major mod is that it doesn't make sense that mesa would come out with two drastically different amps with the same model name.
     
  10. As far as I know, at least Sovtek and Svetlana are currently producing 6550s. I've got a brand new set of Svets in mine (manufactured in 2002). Both companies currently list them as being in production. Enough amps use 6550s to make it worth keeping them in production. So don't sweat it!:D
    An SVT just wouldn't be the same with 6L6s....
     
  11. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Well, I stand corrected (maybe somebody should tell the guys at Ampeg, too...).

    And I ain't sweatin nuffin. I have 3 Boogie amps that all run on 6l6's (and one that runs on EL-84's), and I love them all. They are just a little bit addictive, that's all.
     
  12. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    yes, i believe 6550's are still in production. the problem with mesa amps though is that many of them won't fit inside the chassis, i think they're either too high or too wide. ( a mesa tech told me this)
     
  13. But the real issue is heater current, the 6550's draw 1.6 amps whereas the 6L6 draw 0.9 (IIRC). The heater transformer probably won't handle the extra current.
     
  14. I've seen SLM's (Crate, Ampeg, etc) training, too, and as usual, they're full of it. GE ceased production of 6550A's in 1987. Richardson Electronics, who SLM (Cratepeg) buys their tubes from, bought the factory, the jigs and the leftover mateials and continued to produce 6550A's in the Owensboro, Ky plant until sometime in the 90's when they sold the jigs and material to the Chinese. Richardson 6550A's were never sold to the public in the US but were exported under the Amperex, International, and Richardson names, sometimes labelled as 6550A's, sometimes labelled as KT88's.

    SLM may have CALLED the tubes GE's, but they weren't and you can buy a currently produced tube from Ruby that is made from the SAME old US material on the SAME old US jigs, just assembled in China instead of the US. (They also make Groove Tubes' much ballyhooed "US" 6L6GE.) In addition to this tube branded "Valve Art," Svetlana and Sovtek both make 6550's AND KT88's which will sub for them. EI, JJ, Telsa, and a couple of other Chinese brands also make KT88/or KT88 equivalent tubes which will work as direct drop in subs for 6550's. Sovtek alone makes FOUR different types of 6550!

    They fed you some BS, man.
     
  15. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    man, what suprises me about this whole thing is that the people at mesa never mentioned this at all. they were basically, "yeah, if you can find ones that fit go for it". they also gave me the whole "these tubes aren't made anymore and NOS is hard to find" bit. i specifically asked them if anything needed to be modified on my amp and they told me no. could i have caused some serious damage to my amp if i had followed their advice? can anyone recommend a mesa amp tech who will give it to me straight?
     
  16. But they could've meant to say he could plug in a 7581A (which isn't made anymore I don't think) or a 5881 (plentiful) since both of those are basically 6L6's...however, output power shouldn't go up appreciably, if any.
     
  17. A 7581 is simply a military ruggedized 6L6GC. No more power output, but it will take higher voltages than a run-of-the mill cheapo 6L6GC. A 5881 is the industrial designation for the old 6L6GB and will put out LESS power and be less voltage tolerant. The modern "5881" from Sovtek (which is the same tube Mesa sells) is not really a 5881; it's an old Soviet servo tue that gets CLOSE to the properties of a true 6L6GB but has less output. It is, however, extremely tolerant of high voltages and VERY cheap which makes it popular with amp manufacturers. The ONLY 6L6 family tube (other than the 6550) that will give you any higher output is the KT66, but even it will only increase power on the order of 2-3 watts per tube.

    Mesa likes to pull a lot of cloak and dagger crap concerning their amps, especially the older ones. I'd say that since the original 400's had 6550's, the swap ought to be OK. Mesa would NOT have switched to a cheaper power transformer just to accomodate the change to 6L6's; it would have cost far too much to retool.

    Heater current draw, if it will be damaging, will show up as immediate excessive heating of the power tranny. Even if the draw is too great, it generally won't 'blow-up' the amp immediately. Rather, the heat will gradually burn out the windings over time. If you can place your hand comfortably on the power tranny after it has been run for 15 minutes, it will be fine. Power trannies get warm, and that is normal, but it it burns you, it will burn itself out eventually.

    You will also need to install bias pots to accomdate proper biasing. Mesa's whole "never adjust" biasing is a crock of $hit, and you need the ability to adjust bias current with or without a tube type swap.
     
  18. mthoople

    mthoople

    Nov 1, 2001
    Denver, CO
    I have both a 400 and a D-180. I have new Sovtek 6550WD tubes in the 400. These have a 6L6 size base, allowing the stock clamps to be used. They have plenty of clearance between each other, and clearance to the cover. The D-180 actually has more room under the cover, since the chassis isn't quite as tall.

    Both amps run about 520-540 volts on the plate. Most 6L6 tubes are spec'd for 500V max, but some will handle higher. I have run the D-180 with the 6550's while doing some trouble-shooting, and the tranny barely warmed up at all (I think the D-180/400 trannies are the same).

    6550 tubes in either will require a bias adjustment.

    Mesa wants to sell their tubes, and they don't carry a 6550 anymore. Their recommendation is to use their re-branded Svet 6L6's in these amps.

    Mesa shipped the D-180 with Mesa STR415 tubes. These were supposed to be equivalent to 7581A's for the higher plate voltage.

    Matt
     
  19. BTW, Mesa stole the "STR" designation from the old Sylvania spec for Fender high powered 6L6GC's that could be run upside down. They were "Special Test Requirement" tubes and as such were numbered with an "STR" predesgination. When Philips bought out Sylvania and began JAN 7581 construction, they used the old Sylvania STR as the model for their JAN 7581.

    Mesa's "STR" numbers are an attempt on their part to confuse buyers into believing they are getting an old US type tube. They started it when they intially used the Philips 7581 extensively in their first amps and continued the practice when they switched to the current mostly trash tubes they sell now.
     
  20. stevekim

    stevekim

    Feb 11, 2000
    los angeles, ca
    wow. i love these mesa boogie threads! so much interesting information comes out. so mthoople, what i am thinking of doing is getting a sextet of sovtek 6550wd tubes. with a bias adjustment, will i get more power? i'm only looking to get around 250-275 watts.

    steve


    ps: bagpipes are cool!