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1/4" vs 1/8" aux input

Discussion in 'Amps and Cabs [BG]' started by Seanbassplayer, Jan 18, 2017.


  1. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    I was at my local music shop and was told I can plug my Mesa subway preamp into the aux in on any combo amp that has it if the combo does not have a effects return. My question is there any signal or tone loss using an 1/8" over standard 1/4". Thanks
     
  2. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    There shouldn't be any signal loss, but the 1/4" is just way more secure of a physical connection than the 1/8"
     
  3. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    That's kinda what I thought but wanted to be sure and yes makes sense cause smaller less secure and easier to bent of got knocked by a leg or something. Thx for your reply
     
  4. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Correct, the 1/4" connection is so much more robust that we just couldn't see installing a 1/8" connector on a piece of equipment subject to both musicians as well as the gigging environment.

    The 1/4" preamp output on the Preamp-DI is unbalanced, it would be helpful to know how the ring terminal is connected on the aux input of the combo you plan to use. In general, either a 1/4"TRS to 1/8"TRS, or 1/4"TS to 1/8"TRS should work properly, the 1/4"TRS allows the ring to float at the source (preamp) end so it doesn't matter what happens at the destination (aux in) end.

    The only time the 1/4"TS connection at the preamp might not work is if the tip and ring are connected together at the aux in end without the proper summing resistors provided by the aux in connection. All of our designs include summing resistors for this reason, as well as to properly sum a stereo source.

    Hope this helps.
     
    monsterthompson likes this.
  5. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    Does that mean in theory that if you had an XLR to TRS cable that provided a fully balanced mono signal across two conductors, the summing circuitry could potentially null it out?

    (Of course, dumb idea to do this, but...)
     
  6. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Correct, this would be exactly the result.

    The balanced signal (output) would be represented by one line at +phase and the other line at -phase so if you sum them you would have (+phase)+(-phase)=0phase

    In a normal differential input, the equation would be: (+phase)-(-phase)=2+phase or twice the amplitude of the original signal (with respect to ground). This is how all differential inputs work. Any noise induced on the lines would be common mode and cancel out, any signal on the lines that is differential mode will multiply by 2.
     
  7. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    Yes it helps allot thank you. I was thinking of getting the traynor sb110 which has 1/4" aux input but no effects loop then I see traynor is coming out with a new mini 200 watt combo the sb106 and will be showcased at NAMM this year but it has 1/8" aux input and was wondering if it would be an issue. I'm looking for basically a good practise amp that I can plug in to without going through combo preamp. Thanks again
     
  8. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    Cool! Thanks for answering my question. Now that I think about it, I'm sure people do this from time to time and get confusing results, and blame equipment when it's user error. TRS to XLR cables aren't entirely uncommon, and people might think that they're better than TS to XLR cables because they think TRS makes it balanced, but then they plug it into unbalanced sources. While this would work most of the time, it wouldn't always. If you plug a TRS into a stereo unbalanced output and XLR cable into balanced input in a mixer, I guess you'd have the opposite problem, since the two channels get subtracted at the balanced input and then you'd get most of the audio signal canceled out. And the other case I was thinking about could happen pretty easily, too. Like if I connected one of the line outputs (balanced) from my audio interface to a summing aux input on a bass amp, then there would be full signal cancellation if I used a TRS to TRS cable. Much better to use a regular TS to TS cable in that usage.
     
  9. lz4005

    lz4005

    Oct 22, 2013
    Another thing to think about is that the aux in will usually bypass all the amp's controls, including the master volume, so you would have to control your volume from the pedal.
    When you plug into the effects return you will usually retain use of the master volume.
     
  10. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    So if I get the sb106 should I get 1/4"TS to 1/8"TS or 1/4"TRS to 1/8"TRS or 1/4"TS to 1/8" TRS . Thanks
     
  11. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    Yes I want to by pass the tone controls but now wondering if I will get full power volume still by using volume from mesa subway preamp.
     
  12. lz4005

    lz4005

    Oct 22, 2013
    That all depends on the output from that pre as compared to the output of the internal pre and eq section of the amp.
    Not all amps will respond the same way.
     
  13. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    Thanks maybe agedhorse will have more info on the output volume as he seems to be the mesa man
     
  14. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Correct, and it is in fact one of the things I consider when troubleshooting an interconnection problem with a customer. Often the fault is incorrectly blamed on the equipment because they don't understand how it works.
     
  15. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    On some amps, perhaps, but on "most" amps (including all Genz Benz and Mesa Subways) the aux input returns at the master summing point and is at the same line level, pre master volume control.

    Think of this as a bus input on a mixing console... this is pretty common in the (now old school analog) pro audio world, where I spent much of may career.
     
  16. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I would recommend the TRS to TRS connection since the preamp output intentionally floats the ring connection. The alternative is the TS-TS connection, but it's kind of tough finding 1/8" connectors in the TS configuration (though I do have some here).

    The only drawback to floating the ring connection is if somebody attempts to use the unbalanced output into a TRANSFORMER balanced (floating, not ground referenced) input, though it's not a good practice in general and there is a line level balanced XLR output less than 1 inch away!
     
  17. Seanbassplayer

    Seanbassplayer

    Oct 14, 2016
    Thank you agedhorse. Your info will help me on my quest cheers!!
     
    agedhorse likes this.
  18. nbsipics

    nbsipics Very Unorthodox Behavior Gold Supporting Member

    Apr 8, 2016
    And that's why God invented Speakon for cabs!

    Edit: Living with my eight:88 1/4" no problem Mr Horse :)
     
    Last edited: Jan 18, 2017
    agedhorse likes this.
  19. agedhorse

    agedhorse SUSPENDED Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The Strategy is a legacy class product that does not have the voltage swing on the sleeve of the connector, nor does it have enough contact current to trigger the safety agency rules that drive the requirement for SpeakOn connectors only on the Subways. It's due to national AND international safety legislation, not really a choice if following the rules. Since our products are both UL/CSA and CB Scheme approved, SpeakOns are not optional on products with accessible voltages over the legislated threshold, and with currents high enough to exceed allowable current contact density on connectors.
     
  20. nbsipics

    nbsipics Very Unorthodox Behavior Gold Supporting Member

    Apr 8, 2016
    Hey, I am demonstrably legacy-class myself! And if I can remember what you just said, then I wasn't there :)

    You personally give so many folks on this site what they need/want to hear - my hat's off to you.

    Kids - go to college/shops and try to learn what this dude knows! And realize that Mr. Jobs picked
    a 1/8" jack ( and what, 4 conductors + ground no less?? ) because it added like $500 min less per phone than
    a 1/4" jack ( in any configuration ) would add to the cost. Profits? Quality? Eh, I give up.
     

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