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Stewart World 2.1 - Dead Channel!

Discussion in 'Amps and Cabs [BG]' started by Lonnybass, Oct 22, 2016.


  1. Lonnybass

    Lonnybass

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Last night I ran my Stewart 2.1 in the bridged mono configuration for the first set, worked great, sounded great.

    At some point during the second set, Channel 2 went dead and never came back. I tried recycling the switch, checked the fuse, nothing. No power light, no signal clipping light, completely dead.

    I switched over to stereo and ran my cabinet on Channel 1 during the third set and it sounded fine again, but Channel 2 is now dead as a doornail.

    Does anyone have any suggestions, thoughts on a problem or suggested fix? I opened up the box to see if anything was smoked and nothing seems visibly damaged. Wondering what makes sense to do for a fix. This amp has served me reliably for 16 years and I'd hate to ditch it!

    Lonnybass
     
  2. Time to upgrade to a Class D power amp. Truthfully I fear that the amp may cost more to fix than to replace.
     
    RichSnyder and Coolhandjjl like this.
  3. Lonnybass

    Lonnybass

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    That's my concern as well. Ughhhhhh. This is a sad day.
     
  4. When you lift it’s replacement you won’t consider it as such! :D
     
    R Moses likes this.
  5. I have been going through the process of replacing my working lead sleds with Class D units. The simple reason is to reduce the weight that my agin’ body has to cope with. I chose Carvin units because I have had yeoman service from all my Carvin gear from basses to amps. :)
     
  6. pacojas

    pacojas "FYYA BUN"

    Oct 11, 2009
    MEXICANADAMERICA
    Class H to Class D is anything but an upgrade, truth be told. :cool: the switching frequency of the H is several times quicker resulting in a more musical experience, imo.
    the Stewart amps are supposed to be equipped with protection circuitry to avoid damage to amp and load. perhaps this failsafe function has latched up.
    gl
     
    Last edited: Oct 22, 2016
  7. You said you checked a fuse. My 2.1 has two circuit breakers. Try to reset the Channel-2 circuit breaker (do it with power off!!).

    If you have the wherewithal to do some troubleshooting, you can consider checking power supply voltages by comparing one channel to the other. Realize the amplifier is a dual-mono configuration, so even the power supplies are duplicated. If a power supply seems dead, the protection circuitry could be detecting an output short or circuit failure.
     
  8. Radio

    Radio Gold Supporting Member

    Jan 8, 2010
    New Haven, CT
    IIRC, there is a protection fuse inside for each channel. Replacing this alone is not a fix, probably, if it is in the fault chain, as something else has caused it to blow. I would fix mine if it broke, using the spare in the meantime.
     
  9. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    Careful now...... Amp Weight Comments
     
    petey293 likes this.
  10. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    Yah, I wish I still had my horse. Quick and maneuverable. Aside from permanent installations, every sound support company has or is moving to Class D. And when those sites with permanent installs have a failure of an amp, it gets a Class D replacement. The only market for Class A, A/B, G, or H is hi-fi enthusiasts or those wanting the SVT/Marshall/HiWatt/Orange experience and have the money to do such.

    Are traditional class A/B solid state amps doomed?
     
    Last edited: Oct 23, 2016
    pacojas likes this.
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Really? Would you explain how this is possible, and how it is even comparable?
     
    wcriley likes this.
  12. Lonnybass

    Lonnybass

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    I checked both of the breakers on the rear panel and tried to reset each, neither seems to have tripped. Gonna poke around a little more and see if I can find the fuse and check the voltages with a meter.
     
  13. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    Hey, don't yellow our mellow with that reality carp ;) .
     
    Rich Fiscus, BadExample and agedhorse like this.
  14. Kickass

    Kickass

    Jul 20, 2012
    Scottish Borders
    The manual states "Bridged Mono Mode: Make the appropriate input connection to channel 1 input only (when the Mono/Stereo Switch us in the Mono position, the Channel 2 Input is disengaged)." It also says you need to wire the sp outs in a diffrerent way for Bridg mode:
    "Important: follow these speaker hookup instructions carefully. Failure to do so could damage your amplifier.
    Channel #1 Positive (+) Terminal = Speaker Positive (+)
    Channel #2 Positive (+) Terminal = Speaker Negative (-)
    Channel #1 Negative (-) Terminal = no connection
    Channel #2 Negative (-) Terminal = no connection"

    I hope this helps.
     
    Last edited: Oct 23, 2016
  15. pacojas

    pacojas "FYYA BUN"

    Oct 11, 2009
    MEXICANADAMERICA
    i don't understand the question. i stated an opinion based on having D and H Class amps. if the switching frequency is equal maybe you can explain why my H sounds like a wave file and the D sounds akin to an mp3!
    i dug for answers and apparently was misinformed. :(
     
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Class H doesn't have a switching frequency, the high rail(s) enable and disable with the audio amplitude. Completely unrelated "switching" mechanisms to each other.

    Maybe you simply prefer one amp over the other for an entirely different reason than "switching frequency"?
     
    pacojas likes this.
  17. seamonkey

    seamonkey

    Aug 6, 2004
    Fix or replace?
    That's a tough one. It may be a simple fix, but if you can't figure it out for free it will probably cost at least $100 bench time from a decent tech. That's about 2/3rds the price of buying a new power amp with at least a three year warranty. It's about 1/4th the price of buying one with a 5 year transferable warranty. Both light weight, and more powerful.

    If you sold the amp as broken, or gave it to charity, I'll bet some electronic tinkerer with fix it, and sell it for may $100, buy they are going to be competing with modern amps that are much higher value today. I don't really know what it's worth, but I don't think they are well sought out amps.

    It doesn't sound like you need a bridge amp. You might have fallen into the mindset that more power all the time is needed. Bridging itself probably didn't break the amp, but if you don't need to bridge the the amp may last you years a years if you do nothing.


    I'd say, Mark the channel as bad, and sell it or give it away. Consider if you need to bridge, and get a new amp.
     
  18. Lonnybass

    Lonnybass

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    All was hooked up correctly per the manual (as I have done before), and worked fabulously the first set. The second channel failed during the second set.
     
  19. Boot Soul

    Boot Soul

    Feb 10, 2009
    I have the same amp and years ago, one of the channel trim pots on the front got scratchy and then would cut out in certain positions. I contacted Stewart and they sent me a replacement pot for free. It included a wiring harness from the pot body with a clip in connection. No soldering needed. It seems that a lot of the internals are modular inside these. Try contacting them. They don't make the World amps anymore but they might support them. > http://www.stewartaudio.com/support.php
     
    wave rider and seamonkey like this.
  20. pacojas

    pacojas "FYYA BUN"

    Oct 11, 2009
    MEXICANADAMERICA
    yup!
    i'm not sure where i got the idea that my Stewart 1.2 was Class H with SMPS. their website states the amp is A/B w/high frequency SMPS. perhaps this explains my preferences.
    Stewart Audio - World 1.2
     

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