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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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10-31-2020 06:39 AM
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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.
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Originally Posted by Woody Sound
John
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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.
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Originally Posted by TedBPhx
Danny W.
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Originally Posted by John A.
Last edited by Woody Sound; 11-01-2020 at 01:21 PM.
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Originally Posted by Woody Sound
John
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can always try a cheap adaptor, before any invasive mods
Amazon.com
cheers
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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.
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Originally Posted by KirkP
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 | SweetwaterLast edited by Woody Sound; 11-02-2020 at 09:09 AM.
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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.
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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.
Originally Posted by lawson-stoneLast edited by KirkP; 11-02-2020 at 05:53 PM.
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Originally Posted by Woody Sound
Originally Posted by Woody Sound
Originally Posted by Woody Sound
John
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Originally Posted by John A.
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Originally Posted by Woody Sound
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
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Originally Posted by pingu
gain , simple EQ ,
Phantom Block Quilter Labs
simples
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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.
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Originally Posted by Eck
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-diLast edited by KirkP; 11-04-2020 at 03:16 AM.
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Great article. I think the H&K redbox could be very helpful.
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Originally Posted by KirkP
Hugh is a great teacher
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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.
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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.
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Originally Posted by Woody Sound;[URL="tel:1073017"
perfect
its great when that happens !
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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.
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Originally Posted by KirkP
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Vintage fuzz on "space" transistors
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