Acquiring an SWR SM-900, reasonable?

Discussion in 'Amps and Cabs [BG]' started by baxter_x, Oct 7, 2021.


  1. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    No, the earliest version was bridgable into 8 ohms only. Because it was not the “best” choice, adjustments were made to the design and the later models were bridgable into 4 ohms.
     
    baxter_x likes this.
  2. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    I'm not trying to contradict you in any ways. But all of the SM-900 I found for sell were 4 ohms minimum in bridge mode. Even the oldest ones. Also, the one I'm interested in seems to be among the latest models, not the one from the 90s.
    That's where I'm missing something probably.
     
  3. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I will have to look at my records to verify that I am not mis-remembering from a different model in the line. There is an array of mixing and matching of power transformers and power amp modules throughout the line.

    There was also a version of the SM-900 with two power transformers. I recall that being a later version as well. I do not have all of the data either, some was lost many years ago.

    The number of later models is not very large, and there are several earlier versions. I will look to see what I can find.
     
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  4. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    Thank you very much for your involvement.
    Yes, there was a version of the amp with two power transformer. And I actually wonder if this very one is not one of them. I heard they are among the most reliable.

    Maybe also look by yourself at all the SM-900 for sell currently, and I swear you won't find any with this 8 ohms minimum bridged. Unless I really have to buy a pair of glasses.
     
  5. Dave Hill

    Dave Hill Supporting Member

    Jan 9, 2005
    Atlanta, GA
    Unless they went back and forth, I’m quite sure all the older ones were 4 ohm min in bridge mode. I had three, including a very early one…(SWR Engineering) all 4-ohm. Still have a later, but, pre-Fender model. (SWR Sound)
     
  6. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    You confirm what I witnessed too.
    Would you say it's a reliable amp? Does the last one you have has black and white logo or red and black logo?
     
  7. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    I used to own a 900 with the early "purple" graphics, with the date on the power transformer indicating 1996 build. It bridged into 4 ohms.

    It was rock solid, drove it hard for years. Only sold it because it was way loud for the gigs I started getting. Hugely regretting that move.
     
  8. baxter_x

    baxter_x

    Nov 27, 2013
    EU
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    If the amp was built using the SWR-2000 power amp module, or earlier and has 4 output transistors per module, it should be rated for 8 ohm bridged only. There was a protective limited that prevented (or may prevent) damage driving into 4 ohms bridged, and maybe some versions considered this acceptable for 4 ohm bridged operation but the later versions using the SWR-500/1000 modules with 8 output transistors (same part) were designed specifically for 4 ohm bridged operation.

    This is what my documentation suggests and the circuitry directly supports this premise. The 500/1000 module was designed by Fender (Corona, CA) and it's significantly more robust/advanced. The pre-Fender versions had significant issues with thermal shutdown and failure, the Fender version addressed this specifically, plus it's UL/IEC 60065 compliant.

    Here is the earliest (I believe this was rated at 8 ohms bridged only) and there may have been a version with a single SpeakOn for bridged output too:
    361111B.jpg

    Here's another version (the issue here is that 4 ohms bridged requires 2 ohm minimum load on the dual outputs. In this example, the dual outputs are rated at 4 ohms minimum load. I believe Fender carried this version over during the transition (while figuring out how to revise for compliance) and because there was a large quantity of work in process and inventory:
    0ef3345a-2d94-41d0-9c47-083cdbdb8c44.jpg

    Here's the older versions with the SWR-2000 modules:
    NJI9E7O-iiwB0hKT3u9Up8npV38XOXExtgmsTxeGY4zLtaABXUwiAN_4ssG0rxxr-fZGXLkKhuEyxRCU0JGi42LPvry1O0bm.jpg

    Here's the latest Fender version (I think this was differentiated with the 3 dimensional SWR badge) with the new modules, dual fans and transformers, it is 2 ohm stable in dual mode and 4 ohm stable in bridge mode. It's much more robust:
    fetch?id=872974&d=1510347544.jpg


    Of course, folks are free to believe anything they want to, should they so choose.
     
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  10. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    Thanks a lot for those extremely valuable information.
    I sent an email to the owner to try to guess what version he owns, as it is the 3D logo.
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Verify
     
    baxter_x likes this.
  12. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    I guess you strongly advise me to get this dual transformer version and avoid any other versions right?
     
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    That would be my suggestion.
     
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  14. fast slapper

    fast slapper Supporting Member

    Dec 11, 2001
    Fresno, CA
    The Fender one looks like twice the amp....
     
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  15. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    Well, I asked him if it was a dual transformer/fan version. He told me I should consider another amp......
    I guess this was my last attempt to convince myself I should buy this amp.

    Thanks a lot to all those who took time to guide me and answer my questions.
     
    agedhorse and Al Kraft like this.
  16. Al Kraft

    Al Kraft Supporting Member

    May 2, 2016
    Northern Virginia
    Disappointing for sure, but a good call in the bigger picture IMO.
     
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  17. BassMike14

    BassMike14

    Sep 14, 2021
    I have a SM-400 that I have played for years. I tried three times (recently) to buy a SM-900. Two of them came damaged. Not packed well enough and the mounting ears and hence chassis all bent up. The last one came well packaged in a rack mount but one channel didn't work. One of them, incidentally, they didn't even want shipped back so I will give it to you for the price of shipping. Good for parts, at least. I'm planning to sell my entire SWR rig: sm-400, goliath 4X10 and big ben 18". At 71, I can't really carry that stuff around anymore and busy acquiring a lighter rig. I will say, though, I still and always loved the tone and power. My SM-400 over these cabs was plenty of power, even for outdoor gigs.
     
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  18. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    It's a VERY significant improvement.
     
  19. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    That's extremely nice from you. However I live in Europe so it's a bit of a trip.
    But appreciate, thanks.
     
    BasturdBlaster likes this.
  20. baxter_x

    baxter_x

    Nov 27, 2013
    EU
    I have my eyes on a Mesa M-Pulse 360. I guess this amp is considered as trouble free? No matter the year?
     
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    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
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