Why Would A Solid State Amp Have Impedance Switch?

Discussion in 'The Workbench' started by BowerR64, Jan 12, 2019.

  1. BowerR64

    BowerR64 Well-Known Member

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    Ive been wanting to try one of these older line 6 amp just because of the stereo output and the line 6 edit tool. Ive had one of the XT live pedals and there is something fun about the deep editing on a laptop with the larger screen i enjoy.

    I ordered one used to the guitar center near me and went to pick it up last night and everything seem to work and sound ok. Then i asked if they could check to see if both channels worked and they couldnt get the right channel to work. The left "mono" channel worked but once hooked in stereo both speakers would not put out sound.

    I dont understand the impedance switch on this amp. I understand on tube amps but on SS amps? and why is there only 1 single switch for both channels?

    The manual isnt really clear about this switch.

    Im also wondering if maybe the right channel wasnt working because this switch needs to be in the correct position for stereo operation but for mono this switch might actually do something?

    I always thought Solid state only cared about minimum impedance? Solid state is only finiky when you get to low but anything OVER the minimum was fine?

    flextone 2HD.jpg flextone 1.jpg
     
  2. pedecamp

    pedecamp Well-Known Member

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    Try plugging a 4 ohm cab into a 8 or 16 ohm solid state amp, the amp will burn up. The switch on your amp is a nice feature.
     
  3. Micky

    Micky Well-Known Member VIP Member

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    Heat. It is all about temperature. Running at the incorrect load impedance will generate excessive heat in the power transistors. If you exceed the rating, the transistors burn up. Matching the load to the output keeps things running properly at rated levels.
     
  4. Gutch220

    Gutch220 Active Member

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    ....so you have a cable plugged into the "left" input and one of the "right" inputs and NOTHING works?
    This is odd.
     
  5. Jethro Rocker

    Jethro Rocker Well-Known Member

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    SS amps can tolerate "incorrect" impedances as l;ong as you do not go under the minimum specification. If amp takes 4 ohm minimum don't run it at 2 ohms flat out. But you can run 16 ohms into it HOWEVER, the output is diminished.
    That's why your amp says Same power at all impedances because there is a switch. It likely also wants to see the same impedance on either side. Again, you can go different but won't get 100 watts per side. Why there's no sound in right could be some Mode or Stereo setting on amp? I dunno that part.
     
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  6. BowerR64

    BowerR64 Well-Known Member

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    THis tells me nothing



    No guitar center does, did you read the post? the amp i ordered i wanted tested before i left the store to make sure it worked. One channel didnt work but it worked in mono. I did NOT take the amp home but im wondering if maybe there is something to that impedance switch that defeats the stereo operation.

    Flextone output.jpg
     
  7. Jethro Rocker

    Jethro Rocker Well-Known Member

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    Aha! The picture of the second amp shown has no switch but tells you the output at each impedance setting and lists 4 ohms as the MINIMUM. Anything above that goes. No switch required.
    Doesn't solve your problem though. I'm betting there's a stereo mode somewhere on that thing.
     
  8. BowerR64

    BowerR64 Well-Known Member

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    Yes thats what ive always found also

    Im wondering if the switch is for a "Bridged mode" operation and maybe the switch needs to be at "4 ohms" to work properly in stereo.

    Again ive downloaded the manual for this amp and they dont go into depth on this switch at all. The dont tell you why you need to use it or if its for mono or stereo operation, if its for a certain cabinet they sell

    Another thing that i wondered is that this switch puts an even load on the output.

    You said "the output is diminished" at 16 ohms if the amp can run at 4ohm loads. I wonder if this switch puts the load to match the speaker so the amp always sees minimum load for maximum power
     
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  9. BowerR64

    BowerR64 Well-Known Member

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    That is the first Gen, the one i ordered is the Flextone ii which has the switch and it is the version that guitar center received and we questioned how to hook it up because of that switch. Even the guy at the store was confused because hes use to this on tube amps but not on SS amps and why its there. He couldnt find any info about it either when searching for any info on what speaker cabs to use and where the switch needed to be.

    We tired 2 16 ohm cabs in stereo and tried the switch in both 16 and 8 the right channel never would put out any sound.

    I also wondered about the master volume it felt loose in the chassis and it could be a stacked pot where when turning one knob actually turns 2 pots stacked and it being loose could be why the right channel had no sound?

    I didnt want to risk taking it home to dig into it though i just ordered a different one and thought ide try again.
     
  10. BowerR64

    BowerR64 Well-Known Member

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    Looking at the 2 different amps i think i get what they are doing, the older one ran 4-8 or 16 and the power changed depending on the load.

    I think the newer one with the switch keeps the load so the power amp always sees 8 ohms thats why its always 100 watts.

    So the 4 ohm selection must run a 4 ohm load internally in SERIES creating a total 8 ohm load

    So the 16 ohm setting will run parallel, the 8 ohm setting is a pass threw and the 4 ohm setting runs the 4ohm cab and in internal load in series so the amp always sees 8 ohms

    weird thing to do, never have seen this before, if that is whats happening
     
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  11. Jethro Rocker

    Jethro Rocker Well-Known Member

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    That is my interpretation as well. That is why the older version lists it as varying power at different impedances. The switch gears it to always run at 100 W whether at 4, 8 or 16 ohms. Perhaps the one at GC is simply fucked.
     
  12. RickyLee

    RickyLee Well-Known Member VIP Member

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    I am wondering if that problem one had a bad Cliff jack. The one that switches from stereo to mono if no cable is plugged into one side . . . .


    But it sounds more like the output chips were burned up on the side with no output.
     
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  13. BowerR64

    BowerR64 Well-Known Member

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    Well another thing is the 4 jacks.

    if you set the switch to 4 ohms and you use all 4 jacks? how would that work out? The user would have to do the math and hope its correct

    Im not sure they are old amps, i let them mess with it. They could of needed cleaned or replaced hard to tell.

    I will say this, they just turned around and relisted it. They put it back up as the same wrong listing as the other guitar center as a "bass combo" its clearly not a combo and not for bass

    relisted.jpg

    One thing cool was they refunded my money to a GC gift card, i came home and looked for another one and found another one for $139. so i saved $75. if the second one works? I think i could get that out of it locally when i get tired of it :applause:
     
    Last edited: Jan 12, 2019
  14. BowerR64

    BowerR64 Well-Known Member

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    The old one (purple) ran 4ohm minimum it has fans

    The newer one flextone ii only runs at 8 ohms using the switch it has no fans.

    Ide bet if it had the same cooling it would run at 4 like the older one though. Ide even bet they are the same output chips just the flextone 2 can run with the line 6 edit on the PC threw the midi cables the original one didnt have that.

    4ohm 8 ohm.jpg
     
  15. Jethro Rocker

    Jethro Rocker Well-Known Member

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    There is no 4, 8, 16 ohm switch on the new one? No chart showing output at 4 ohms??

     
  16. BowerR64

    BowerR64 Well-Known Member

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    Yeah the first Flextone amp head they made was like that purple one i think that purple tolex might of been a special thing or some one recovered it idk. That first one has the fans and no impedance switch plug and go

    The second one, thats the one im wanting has the switch, no fans but it has the midi in/out and works with the line 6 edit software

    Line 6 edit.jpg
     
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  17. ampmadscientist

    ampmadscientist Well-Known Member

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    Some solid state circuits do have an output transformer.

    But a solid state circuit will only have full power at a certain load. (example 4 ohms)
    and if the load is 1/2 of that (example 8 ohms) it will only push 1/2 power.

    That may be why there is a ohms selector, to push full power at changeable loads.
     
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  18. BowerR64

    BowerR64 Well-Known Member

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    What i meant was on tube amps the ohm switch changed the taps on the transformer. Your saying some solid state do the same thing?

    And half power? I knew it was diminished a little but i didnt think it was by half

    I figured from 4 to 16 would be closer to half but not from 4 to 8
     
  19. ampmadscientist

    ampmadscientist Well-Known Member

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    8 is half the load of 4 ohms.
    Some solid state amps do have OP transformers.
    I suppose open it and look inside.
     
  20. johan.b

    johan.b Well-Known Member

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    Line 6 wanted full output at all impedance so they switched the internal voltages in those amps..later on the changed that..I guess they found out it was a setup for (amp)failure, when customers ran 4ohm speakers and amp set for 16
    J
     
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