aculous Posted February 12, 2016 Report Share Posted February 12, 2016 So I just bought a set of JBL LSR308s, powered studio monitors. http://www.jblpro.com/www/products/recording-broadcast/3-series/lsr308#.Vr38ipP8uk0 they have a switch on the back that allows me to run -10dB for consumer connections I am guessing and +4dB for pro audio stuff...they are powered monitors so I have a 1/4" TRS hookup in the back and an XLR hookup and thats it. When I run it at -10dB I can't hear them...at +4dB they are distorted. (I am running from my headphone out on my computer) So my question is do I need a pre-amp? or do I just need a mixer or Focusrite 2i4 or whatever to give them a full +4dB signal? (I also entertained the possibility its the cable I am using but I really doubt it, its brand new and decent quality) Link to comment Share on other sites More sharing options...
Knocker Posted February 12, 2016 Report Share Posted February 12, 2016 Pro audio is standardized to 1.23 volts. Consumer audio is standardized to .316 volts. You probably want to get either a pre-amp or a mixer to raise the signal voltage. A simple pre-amp would do the trick but that Focusrite is a badass little two channel mic pre-amp that you could use for recording with those combination XLR- 1/4 inch inputs. Also has phantom power for condenser microphones. If you don't plan on doing any recording a simple pre-amp would probably be cheaper. A mixer will obviously have a pre-amp built in and could be more useful for other projects. Here is some more information I found in regard to your question. Link to comment Share on other sites More sharing options...
Knocker Posted February 12, 2016 Report Share Posted February 12, 2016 Also I'm curious as to if when you were experiencing distortion if the volume on your computer was turned all the way up. Too high of volume in a digital setting can cause digital distortion which is horrible as digital has zero headroom if you exceed the number of bits available. Curious as to if you backed off on the volume on the computer, that you could then turn up the gain on your speakers without any audible distortion. Edit: Also it's possible that the opposite is happening. Meaning that the setting on the speaker that ended up being distorted is due to the setting increasing the input sensitivity on the speaker amp to the point that the inputs are being overloaded by the output of the headphone jack, causing distortion. Once again, meaning it may be a good idea to turn down the computer. If either is the case then you might not need to purchase a separate pre-amp. Link to comment Share on other sites More sharing options...
aculous Posted February 13, 2016 Author Report Share Posted February 13, 2016 Also I'm curious as to if when you were experiencing distortion if the volume on your computer was turned all the way up. Too high of volume in a digital setting can cause digital distortion which is horrible as digital has zero headroom if you exceed the number of bits available. Curious as to if you backed off on the volume on the computer, that you could then turn up the gain on your speakers without any audible distortion. Edit: Also it's possible that the opposite is happening. Meaning that the setting on the speaker that ended up being distorted is due to the setting increasing the input sensitivity on the speaker amp to the point that the inputs are being overloaded by the output of the headphone jack, causing distortion. Once again, meaning it may be a good idea to turn down the computer. If either is the case then you might not need to purchase a separate pre-amp. I've been playing with the Gain structure if you wanna call it that and yea distortion no matter what so far. Scenario 1: volume at 5 (or 50% position) on the speakers volume at 50 on computer and input sensitivity at -10dB audible hiss Scenario 2: all of the above but sensitivity at +4dB audible hiss Scenario 3: volume at 6 on the speakers volume all the way up on the computer audible hiss I think is the issue is with balanced to an unbalanced connections or the DAC? dunno. That and the fact that my computer's audio port most likely is crap. Running out to guitar center to get a Focusrite Scarlet Audio Interface or maybe a mixer today. Hooked up to a mixer in store I know they don't hiss...sooo its either my specific set which I highly doubt or I just need a better setup. Link to comment Share on other sites More sharing options...
Knocker Posted February 13, 2016 Report Share Posted February 13, 2016 I wonder if it would hiss if you plugged the speakers directly into your phone's audio jack. Link to comment Share on other sites More sharing options...
STEvil Posted February 13, 2016 Report Share Posted February 13, 2016 Is the output source on the PC from an onboard soundcard or a pci/pci-e card? Some ports are amplified for headphone use, you may want to try a different one. MickyMcD - "Capable of making some serious trouser flapping volumes at where's-my-testicles frequencies, the Servo-Drives used to be fairly jaw dropping..." Any time you have have a power wire next to your frame put some rubber hosing (or cut up an innertube) around it. The wire is bound to wiggle (due to driving or flex) and the casing will eventually wear through. Hammerdown... 1% no links to outside websites, business related FB/YT pages allowed. Link to comment Share on other sites More sharing options...
Knocker Posted February 13, 2016 Report Share Posted February 13, 2016 I remember having a mini notebook with a sound card that sounded so bad I wasn't even allowed to plug it in to the mixing board at work.. Ended up just going with a little USB sound card. Fixed the problem right up. Link to comment Share on other sites More sharing options...
aculous Posted February 16, 2016 Author Report Share Posted February 16, 2016 Is the output source on the PC from an onboard soundcard or a pci/pci-e card? Some ports are amplified for headphone use, you may want to try a different one. Onboard realtek on a AsRock v77 Intel board. I remember having a mini notebook with a sound card that sounded so bad I wasn't even allowed to plug it in to the mixing board at work.. Ended up just going with a little USB sound card. Fixed the problem right up. I have a Creative USB soundcard, I'll try that too tonight. Probably just pick up the focusrite though, I think these things need a amp really though. They are a little power hungry, and I am not sure I can bypass the integrated amp. Link to comment Share on other sites More sharing options...
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