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  1. #1

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    Can I swap in an xlr/1/4" combo jack for a plain xlr jack? (In an acoustic amp?) Or is the wiring completely different?
    Last edited by Woody Sound; 10-31-2020 at 06:58 AM.

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    The Jazz Guitar Chord Dictionary
     
  3. #2

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    Xlr is balanced, meaning there are three wires: hot, neutral, and ground.
    1/4” only has 2; hot and neutral.

    So an xlr to 1/4” converter cable is wired with the ground wire (or shield, depending on the type of wire used) soldered together with the neutral on the ground terminal of the 1/4” jack.

    Most xlr cables are wired in standard configuration anyway, so it should be just fine.

    If you want to make sure, just unscrew the connector and check the color of wires and the number of pins (visible inside the connector) match.
    Usually,
    ground/shield (left)
    negative (center/top)
    positive (right)
    for the male side, and the mirror opposite for the female side.

    Sometimes they are wired differently (+/- switched), but as long as the other side matches, it’s ok.

    * edited to make it a little less confusing.
    Last edited by Zhahn; 10-31-2020 at 08:45 AM.

  4. #3

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    Quote Originally Posted by Woody Sound
    Can I swap in an xlr/1/4" combo jack for a plain xlr jack? (In an acoustic amp?) Or is the wiring completely different?
    They're wired differently. A combo Jack is two jacks with different wiring in one housing, connected to some sort of switching circuitry that detects which type of plug is connected. The XLR part is balanced and carries phantom power for condenser mics (usually); the 1/4" part (usually) is unbalanced, often connected to a different input circuit with different impedence, and does not carry phantom power. To swap in a simple XLR, you'd have to know how to deal with the 1/4" part of the circuit. It might be OK to just cut the wires, but it might not.

    John

  5. #4

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    Tangentially

    On the Rosette Acoustic amp Mesa uses an XLR and a 1/4” with a switch to select which one to use. They claim those combo jacks end up with noise in both circuits.

  6. #5

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    Quote Originally Posted by TedBPhx
    Tangentially

    On the Rosette Acoustic amp Mesa uses an XLR and a 1/4” with a switch to select which one to use. They claim those combo jacks end up with noise in both circuits.
    My Acoustic Image amps have combo jacks and they're as quiet as could be.

    Danny W.

  7. #6
    Quote Originally Posted by John A.
    They're wired differently. A combo Jack is two jacks with different wiring in one housing, connected to some sort of switching circuitry that detects which type of plug is connected. The XLR part is balanced and carries phantom power for condenser mics (usually); the 1/4" part (usually) is unbalanced, often connected to a different input circuit with different impedence, and does not carry phantom power. To swap in a simple XLR, you'd have to know how to deal with the 1/4" part of the circuit. It might be OK to just cut the wires, but it might not.

    John
    Thanks, but I was wondering about swapping IN a combo jack for the existing simple xlr.
    Last edited by Woody Sound; 11-01-2020 at 01:21 PM.

  8. #7

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    Quote Originally Posted by Woody Sound
    Thanks, but I was wondering about swapping IN a combo jack for the existing simple xlr.
    Sorry. if you're only going to use the XLR part, then you can connect the XLR wires in the amp to the XLR terminals on the jack. If you want to use the 1/4" part as well, you'd have to figure out how to wire that in to deal properly with phantom power and switching (which I don't know how to do). Note that in most devices that have the combos, the two jacks are going to different circuitry, and if you want, say, a high impedence input for magnetic pickup there's more to it than just the combo jack. You need to have a whole other input circuit and a way to switch between the two.

    John

  9. #8

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    can always try a cheap adaptor, before any invasive mods



    Amazon.com

    cheers

  10. #9

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    I’ll assume you want to plug a typical guitar into it. That adapter might work, but there are a couple of issues to consider:
    1) If your amp has phantom power it could potentially fry any device not designed for phantom power. You can probably switch off phantom power, but it would be safer to put a capacitor in series with the center conductor to block DC while passing the signal. More info here (although they use two conductors in the shielded cable):
    Phantom Power Blocker (protect Your Dynamic Microphones) : 5 Steps - Instructables
    You can buy phantom power blockers, but the one I find at Amazon is $44.
    2) Your amp is probably designed for a low impedance microphone. Magnetic pickups are high impedance and the mismatch might sound poor. That issue won’t harm your equipment though.
    It might help to give more detail about the amp and what you want to plug into it. If you want to play something like a humbucker through an amp designed for microphone input, I’d consider a pedal designed for that.

  11. #10
    Quote Originally Posted by KirkP
    I’ll assume you want to plug a typical guitar into it. That adapter might work, but there are a couple of issues to consider:
    1) If your amp has phantom power it could potentially fry any device not designed for phantom power. You can probably switch off phantom power, but it would be safer to put a capacitor in series with the center conductor to block DC while passing the signal. More info here (although they use two conductors in the shielded cable):
    Phantom Power Blocker (protect Your Dynamic Microphones) : 5 Steps - Instructables
    You can buy phantom power blockers, but the one I find at Amazon is $44.
    2) Your amp is probably designed for a low impedance microphone. Magnetic pickups are high impedance and the mismatch might sound poor. That issue won’t harm your equipment though.
    It might help to give more detail about the amp and what you want to plug into it. If you want to play something like a humbucker through an amp designed for microphone input, I’d consider a pedal designed for that.
    Thanks. I want to plug in a "regular" guitar into the xlr jack on an "acoustic" amp. I tried one of these, but it sounds horrible, ultra sensitive, can even hear pot noise when adjusting anything on the guitar.

    D'Addario PW-P047Z XLR Male to 1/4" Female Balanced Adapter | Sweetwater

    Maybe there's a plug-in adapter that actually fixes the impedance mismatch?

    I see a lot of low-to-high adapters but not many high-to-low adapters.


    I wonder if something like this would work? But a plug-in adapter sure would be more convenient.

    Behringer Ultra-DI DI400P 1-channel Passive Instrument Direct Box | Sweetwater
    Last edited by Woody Sound; 11-02-2020 at 09:09 AM.

  12. #11

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    This is not a good idea. Using the linked adapter to connect to an XLR output on an amp can work, but connecting a magnetic pickup to an input expecting a microphone will not give a pleasing sound. If you want to put in a combo jack, you need to rewire the amp to direct the input from the 1/4" plug to the 1/4" input that is already there, or thereabouts. The impedance and voltage levels are different, and without redesigning the circuit it will sound bad, and perhaps damage the components, depending on the amp design. It's possible to make an adapter that takes care of all this, and perhaps such an adapter exists, but I've never bothered to look for one.

  13. #12

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    I think you need a DI box and preamp that emulates a guitar amp. I’m sure there are many products that combine the two in a single rack mount or pedal, but I haven’t ever researched that.

    Here’s an idea—Buy a Quilter Interblock 45 and and adapter to convert the 1/4” balanced (TRS) output to XLR. (The Quilter has a built-in DI, so you should only need the adapter and a TRS cable between the Quilter and adapter.) Quilter preamps seem to have a great reputation. You could use it as the preamp for your acoustic amp, leaving the 45 watt speaker output disconnected. But the Quilter could also be used as a head with a separate speaker cabinet. It might come in handy to have that flexibility. I’ve never used Quilter products so this is not an endorsement, just an idea.
    Quilter Labs InterBlock 45 45-watt Head | Sweetwater

    There was a thread on the Interblock 45 last year.
    Quote Originally Posted by lawson-stone
    So I like the idea of a tiny little amp that can serve as a direct box for playing through other systems, but still having EQ and a bit of "character" as well, but also being able to drive a speaker and serve as a mini-rig. The Quilter Interblock 45 seemed a good candidate for that task, so I found a "floor demo" model in like-new condition for a bit less than list price. I still haven't fathomed all its features, but thought I could go ahead and post a demo of a matter that is important to me: how does the DI signal sound compared with a speaker? .....
    Last edited by KirkP; 11-02-2020 at 05:53 PM.

  14. #13

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    Quote Originally Posted by Woody Sound
    Thanks. I want to plug in a "regular" guitar into the xlr jack on an "acoustic" amp. I tried one of these, but it sounds horrible, ultra sensitive, can even hear pot noise when adjusting anything on the guitar.

    D'Addario PW-P047Z XLR Male to 1/4" Female Balanced Adapter | Sweetwater

    Maybe there's a plug-in adapter that actually fixes the impedance mismatch?

    I see a lot of low-to-high adapters but not many high-to-low adapters.
    I don't think I've ever seen an inline converter that goes from 1/4" to XLR and also does the impedance conversion. For impedance conversion, I think I've only ever seen DI boxes and various direct recording preamps.

    Quote Originally Posted by Woody Sound
    I wonder if something like this would work? But a plug-in adapter sure would be more convenient.
    Maybe, but there's not much of a market for your use case. The typical uses are either a splitter that sends a balanced/low-impedance signal to a mixer and a high impedance signal to a guitar amp (i.e., a DI box) or a device that does some sort of tone shaping (often, including guitar speaker emulation) of a guitar signal before going into a recorder or PA-style amp. If what you're trying to do is get an electric guitar + acoustic amp to sound like an electric guitar + traditional guitar amp, there's more to it than just adapting the plug and matching the impedances. An acoustic amp is a different device designed for a different purposes from an electric guitar amp. Some of these give you a bit of both worlds (e.g., by having combo plugs, switchable tweeters, and tone and gain controls that work a bit better with magnetic pickups), but if you're using one that is strictly an acoustic amp, or is really a PA and not a guitar amp of any kind, it's not likely to work well without some sort of outboard tone shaping..

    That will do the plug and impedance conversion and might sound better than plugging is with just an adaptor, but might not (depending on the the acoustic amp's tone controls, gain structure, and speaker). There's a reason some people often don't like the sound of acoustic amps with magnetic pickups (e.g., moi).

    John

  15. #14
    Quote Originally Posted by John A.
    I don't think I've ever seen an inline converter that goes from 1/4" to XLR and also does the impedance conversion. For impedance conversion, I think I've only ever seen DI boxes and various direct recording preamps.



    Maybe, but there's not much of a market for your use case. The typical uses are either a splitter that sends a balanced/low-impedance signal to a mixer and a high impedance signal to a guitar amp (i.e., a DI box) or a device that does some sort of tone shaping (often, including guitar speaker emulation) of a guitar signal before going into a recorder or PA-style amp. If what you're trying to do is get an electric guitar + acoustic amp to sound like an electric guitar + traditional guitar amp, there's more to it than just adapting the plug and matching the impedances. An acoustic amp is a different device designed for a different purposes from an electric guitar amp. Some of these give you a bit of both worlds (e.g., by having combo plugs, switchable tweeters, and tone and gain controls that work a bit better with magnetic pickups), but if you're using one that is strictly an acoustic amp, or is really a PA and not a guitar amp of any kind, it's not likely to work well without some sort of outboard tone shaping..



    That will do the plug and impedance conversion and might sound better than plugging is with just an adaptor, but might not (depending on the the acoustic amp's tone controls, gain structure, and speaker). There's a reason some people often don't like the sound of acoustic amps with magnetic pickups (e.g., moi).

    John
    I like the acoustic sound, just want it to work.

  16. #15

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    Quote Originally Posted by Woody Sound
    I like the acoustic sound, just want it to work.
    so you want to plug a guitar into the XLR (mic) input of an acoustic amp ?

    cool yes you can use a DI box (it matches the impedance correctly)
    (a passive one won't require phantom power from the XLR)
    yes indeed like the suggested behringer. .....

    Behringer Ultra-DI DI400P 1-channel Passive Instrument Direct Box | Sweetwater

  17. #16

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    Quote Originally Posted by pingu
    so you want to plug a guitar into the XLR (mic) input of an acoustic amp ?

    cool yes you can use a DI box (it matches the impedance correctly)
    (a passive one won't require phantom power from the XLR)
    yes indeed like the suggested behringer. .....

    Behringer Ultra-DI DI400P 1-channel Passive Instrument Direct Box | Sweetwater
    or here's an active DI with 3 different powering options
    gain , simple EQ ,
    Phantom Block Quilter Labs

    simples

  18. #17

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    I have a Behringer DI box. It’s terrible and I may just bust the housing to build my own. I suspect DI boxes are not that easy to make in good quality so go with reputable brand.


    Sent from my iPhone using Tapatalk

  19. #18

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    Quote Originally Posted by Eck
    I have a Behringer DI box. It’s terrible and I may just bust the housing to build my own. I suspect DI boxes are not that easy to make in good quality so go with reputable brand.


    Sent from my iPhone using Tapatalk
    A passive DI is just a balun transformer and three connectors in a box.
    http://www.nfaudio.com/wp-content/uploads/DIY-DI.pdf
    I don’t know how to select the transformer though. They do vary in quality.

    I think a magnetic pickup is likely to sound better with an active DI than a passive one, since it will have a better impedance match. But if you put a buffered pedal between your guitar and a passive DI I think that is roughly equivalent to having an active DI.

    Much more about DIs here:
    https://www.soundonsound.com/techniques/prepare-di
    Last edited by KirkP; 11-04-2020 at 03:16 AM.

  20. #19

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    Great article. I think the H&K redbox could be very helpful.


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  21. #20

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    Quote Originally Posted by KirkP
    yes that is a superb explanation ....
    Hugh is a great teacher

  22. #21
    Well something was clawing at my memory, so I went digging through my old parts bins and found this, still sealed. Must have been there for 10 years or so. Seems to be working great so far.

    Changing an xlr to a combo jack?-di-box-jpg

  23. #22

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    FWIW, the Line6 Relay G10 wireless system receiver has both XLR and 1/4" unbalanced outputs. I've used both, and they both sound pretty good when connected to intended amplifiers. I've run the XLR output to a PA, using various guitars with magnetic pickups, and while they don't sound as good that way as through a standard guitar amp, they're acceptable. I haven't used a cable in a long time, other than connecting the wireless receiver through pedals (rarely) to amps. I hate to beat dead horses, but I really, really like being wireless, for multiple reasons.

  24. #23

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    Quote Originally Posted by Woody Sound;[URL="tel:1073017"
    1073017[/URL]]Well something was clawing at my memory, so I went digging through my old parts bins and found this, still sealed. Must have been there for 10 years or so. Seems to be working great so far.

    Changing an xlr to a combo jack?-di-box-jpg
    ha !
    perfect
    its great when that happens !

  25. #24

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    I did a quick search for listening tests of various passive DIs with passive magnetic pickups and found this.
    The Great Direct Box Comparison with Audio Samples
    They use a bass guitar, though. I haven’t listened, but they report significant differences between them. But those differences might be specific to each instrument that is plugged into them, since the impedances of the pickup and DI are coupled. With an active DI (or active pickup) that coupling would be pretty much eliminated.

  26. #25

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    Quote Originally Posted by KirkP View Post
    I did a quick search for listening tests of various passive DIs with passive magnetic pickups and found this.
    The Great Direct Box Comparison with Audio Samples
    They use a bass guitar, though. I haven’t listened, but they report significant differences between them. But those differences might be specific to each instrument that is plugged into them, since the impedances of the pickup and DI are coupled. With an active DI (or active pickup) that coupling would be pretty much eliminated.
    Sounds very useful to me. The Sound in Sound article mentions guitar amps have a resonance in their input circuit that helps guitar mids cut through, but I think for jazz guitar this is not helpful given the amount of bass amps that sound great. Apart from that the amount impedance matching should work for both.


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