SWR Baby Blue Head....hot enough to cook on!

Discussion in 'Amps and Cabs [BG]' started by armybass, May 26, 2012.

  1. armybass

    armybass Gold Supporting Member

    Jul 19, 2001
    I know that this has been discussed many times and I know that it is common knowledge that these little amps are known to get hot....but my goodness it scares me how hot mine gets. I only use it on occasions with my 4ohm SWR Goliath Jr because I love the amp and I want it to last forever. We played a three hour gig last night and I was once again shocked at how hot the amp was so I started shutting it off between sets. I do not know if that will help preserve the life of the amp. I think I am going to add a little fan when I gig with this amp.
  2. I love the sound of my SWR working man 300, but I don't trust it to gig with BECAUSE it gets so hot. I "let the smoke out" at a huge gig several summers back. I bought a new one and use it only for rehearsals. It truly is shocking how hot they get! I never understood SWR's decision to not put an on board fan in these guys. I use a small fan now and blow it on the heat sinks when I use it. So far, so good.
  3. basskillah


    Sep 14, 2004
    Peyton, CO
    The aluminum case was designed as a heatsink. It draws the heat away from the electrical components, thus making the outside case hot. This is not a accident, it was engineering. As long as you keep your hands on your bass, and not on your amp case all night, you should be fine lol!
  4. chadds


    Mar 18, 2000
    See if a tech can determine if it's caps are good and if it's bias is in spec. Other than that just enjoy. The shell is a heat sink so it's warm. I've played two SM-400s in hot sun for hours and they never failed. Is it in the original rack case?
    A fan can't hurt anyway.
    I have a II and it has that vent on top but that's all. I've had that since new and it's actually seen more gig time than any larger amps.
  5. All amps need heatsinks. Using the case as a heatsink, IMHO, *could* be considered "engineering"...as in "value engineering", or in other words, making it cheaper. Maybe smaller and lighter too, but I lean towards "cheaper".
    But that's just my opinion.

    Heat and electronics do not go well together. External heatsinks and a fan keeps amps cool. Dunno why an amp manufacturer would scrimp. My old Kustom K-250 had the output transistors mounted on a small aluminum piece inside the amp at the bottom, with no heat flow, and the head would get insanely hot.
  6. wave rider

    wave rider

    Jan 5, 2005
  7. Here's a post I did over in the SWR AE bypass thread showing how I installed a couple fans in my BBB II.


    As far as if the aluminum chassis being a heat sink was good engineering or not I'm of the thought NO. Heat is the enemy of solid state electronics. When the whole chassis heats up it raises the ambient temp inside the amp which will take its toll on all the electrolytic caps. I'm much happier feeling the hot air blow out the top of my Baby Blue II and the chassis barely feeling warm after a 3 set gig night.

    The fact that Steve Rabe later modified the SM400 with adding a fan to the SM400S tells me that was an Ooops.

    To the OP, your right in turning your amp off between sets. The idle current and tube will continue to contribute to the heat inside the amp even when your not playing. If you had fans installed it would be best to leave it on so the fans can do their job. My BBII has the fans powered by an independent power supply so I can shut the amp down between sets and leave the fans on. I haven't had to do that yet as the fans work so well even with the amp on all night.
  8. The aluminum-chassis-as-heatsink approach would not make sense in terms of cost cutting. The aluminum is more expensive than steel. That said, they can get very warm to the touch (as do the other early models). The SM400S had a fan added to cope with the additional heat produced by more output power (compared to the non-S original). The S also brought a revised heatsink and venting arrangement to the chassis and case of that model.

    The EB head is also encased within a wooden/ratfur covered box, which also has vents. It might be some concern, but it also might not.

    Want another option to keep it cool? Run it into an 8 ohm load instead of 4 ohm. I've run mine into either without problem for hours. When into a 4 ohm load it does get warmer, as expected.
  9. jungleheat

    jungleheat Inactive

    Jun 19, 2011
    You don't necessarily have to put a fan IN the amp. A small fan blowing across the top should do the trick. I've done something similar with my stereo setup. I had a SONY ES amp running my sub, and a Soundstream DA-2 running my 2 pairs of JBLs (which sounded amazing by the way). I can't remember which one I used it on, but I had a little small computer fan with it's own AC plug and I set it on top of one of the amps on the edge in the back corner, so it would blow diagonally across the top to keep it cool. Worked great and I could drive those amps HARD for a long time without any problems.
  10. basskillah


    Sep 14, 2004
    Peyton, CO
    Aluminum is not inexpensive
  11. chaosMK


    May 26, 2005
    Albuquerque, NM
    Too much hip thrust
    Just get a $5-10 compact "outboard" fan and it'll make a big difference.

    The fan went out on one of my big tube amps and I've been using a small inexpensive external fan... runs great, stays cool.
  12. I know, aluminum is not inexpensive, BUT...the amp has to have a case.

    And aluminum heat sinks ARE expensive. Ever priced them? I have, they can be more expensive than an all-aluminum enclosure.

    So it would be cheaper in the long run to downsize (or eliminate) the heatsinks and hope an aluminum chassis (or even a steel one) can provide enough heat sinking to keep the amp alive. Fewer parts, simpler to make.

    In other words, I still call it a cost cutting move.
  13. rapidfirerob

    rapidfirerob Fusion rules!

    I believe they sold the Baby Blue with a waffle iron option for a time.
  14. I have a SWR Workingman 300 and I gig with him. I put a fan to keep the amp cool.

    This is the fan and the amp.


    Those are rather unique speakers.... What are they?
  15. It's the original speaker just have to recoine the center and that what I have available.
  16. chadds


    Mar 18, 2000
    I'd have the bias checked and the caps. I gigged three times a week with my BBII with no surprising warmth and not the temp am SM-400 would attain.

    Mine is still in service bought new in the '80s. It has had a cap job. I've rolled 12Ax7s through it for fun. It's gone through the Bag Ends, the Celestions and it can't abuse the LDS long throw 8"s. :) I was using a Guild Ashbory and am pretty sure that was the cause of their demise. Wear and tear. :eek::bassist:

    Have a tech look at it. Before you go fanning it. :)
  17. BassmanPaul

    BassmanPaul Inactive

    The Ashbury has a Piezo pickup and the subharmonics from those are a speaker killer. To use that you should invest in a high pass filter to cut the subs out of the signal chain. I have a similar problem with a bass that has Piezos in the bridge saddles.
  18. chadds


    Mar 18, 2000
    Oh I know it!!
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