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  • Positive Grid Bias (PC) into Amp Cab for live rig

    I'm planning out a future live/rehearsal rig, and want the flexibility and versatility of Bias Amp/FX but the tonal characteristics of a physical cab. My question, is; What product(s) would safely and cleanly get my signal from my PC to a cabinet? Currently, I run Guitar -> Steinberg UR22mkII -> Microsoft Surface -> Cubase 8 w/ Bias -> JBL LSR monitor pair.

    If I'm understanding things, I should be able to run a line out to the effects loop return on a combo amp to bypass the Pre and utilize that amp's Power amp. Is that correct? If so, I've got my eye on a few Mesa/Boogie 212 combos (Nomad 55 or Express 5:50).

    To cover my bases though, how would I approach this when using a 4x12 cab?


  • #2
    I don't know enough to know whether what you have in mind will work but the effects loop doesn't normally bypass the preamp. The loop comes before the tone controls. What you have in mind is an amp with preamp out/power amp in jacks. Neither Mesa you're considering has such jacks. I know some Peavey and Fender amps do. I think you might be better served by a powered speaker since you're using cab emulation anyway.
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    • #3
      Thanks DeepEnd, That cleared a few things up. Eventually, I want to upgrade to the Bias Head, and run that into a Mesa 4x12, but that's a bit much for my current needs, so I'm trying to figure out where to invest my time and money first.

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      • #4
        Originally posted by DeepEnd View Post
        I don't know enough to know whether what you have in mind will work but the effects loop doesn't normally bypass the preamp. The loop comes before the tone controls. What you have in mind is an amp with preamp out/power amp in jacks. Neither Mesa you're considering has such jacks. I know some Peavey and Fender amps do. I think you might be better served by a powered speaker since you're using cab emulation anyway.
        The effects loop splits the preamp from the power amp in nearly all amps.

        The Effects return (or send) Has a switched jack which disconnects the preamp from the power amp.

        He can indeed plug into the effects return jack and drive only the power amp.

        There are two factors however. One is this connection may or may not come after the master volume. If it comes after the master volume he will be connected to a power amp running full power which may or may not be too loud.

        Second, a sound card outputs a line level signal and effects loops tend to be instrument level. Again, the signal may be too loud and a -10dB pad may be needed to bring line level down to instrument level.

        Third, some effects loops run in parallel or have series/parallel options. You want to be sure the effects loop is running series if it has a switchable option. My Marshall for example has a serial/parallel switch on the front and a mix pot so I can run either plus I can adjust from full dry to full wet.
        I can use this knob to adjust the loop return levels to work at line or instrument levels. To be sure read your manual.

        As an option you can use an attenuator between the interface output and amp so you can run a strong signal into am amp without overdriving it. http://www.parts-express.com/harriso...-pair--266-242
        You can then adjust the computers output to medium/normal level and set the amps gain like you have an instrument plugged in which seems to be your objective.

        They make -3, -6, -12dB pads. -3 might not be enough but you could connect the pair in series for -6dB
        A single -6dB pad should be enough. (Two of those in series is -12dB)
        There's not a huge difference between instrument and line Level plus you have gain controls. I'm sure -6 will do the job fine

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        • #5
          Originally posted by dthines84 View Post
          I'm planning out a future live/rehearsal rig, and want the flexibility and versatility of Bias Amp/FX but the tonal characteristics of a physical cab. My question, is; What product(s) would safely and cleanly get my signal from my PC to a cabinet? Currently, I run Guitar -> Steinberg UR22mkII -> Microsoft Surface -> Cubase 8 w/ Bias -> JBL LSR monitor pair.

          If I'm understanding things, I should be able to run a line out to the effects loop return on a combo amp to bypass the Pre and utilize that amp's Power amp. Is that correct? If so, I've got my eye on a few Mesa/Boogie 212 combos (Nomad 55 or Express 5:50).

          To cover my bases though, how would I approach this when using a 4x12 cab?
          I would recommend sticking with a PA speaker for live/rehearsals. I have a solid state amp and computer hosted guitar sims run through effects loop sound good. Not as good as they sound played through a monitor or PA speaker. My solid state amp has a PA speaker in it. You notice as you swap out cabinet simulations that the overall tone does not change as much as it does with a monitor speaker or PA. You can buy a PA speaker for between $300 - $600 that will meet all your needs.

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          • #6
            The simplest method would be to buy a power head like a Crown and simply run it into a cab. If you want tube tone a few amp manufacturers like Mesa make tube power amps for this purpose. The front end is going to be the computer using virtual guitar amps and plug in effects and the interface as a preamp. You could put effects and an EQ before the power amp so you could tweak the power amp and speaker response.

            I don't know how well that setup will work. The computer latency would drive me bonkers. With an analog setup string attack is nearly instantaneous. Passing a guitar through a computer takes time to be converted to binary, processed by the CPU and have that software modify the signal using algorithms, then sent back out and converted to analog. I haven't been able to do that in less then 100ms with a high end quad core and the latency gets worse as you add more effects because you have to perform more math formulas on the data.

            I haven't acquired a thunderbolt interface for that quad core yet. Thunderbolt 3 is 40 Gigabytes per second compared to USB 2 which is 60 megabytes per second. That port speed may make the difference in getting closer to real time, but that increase in speed isn't the only cause of latency. An interface only deconstructs and reconstructs the data from analog to binary and back and moves it to the main bus. You still have all the other things that go on inside a computer which take time and as I said as you add more virtual effects the turn around time goes up.

            I'll stick with an analog rig playing live. I've never gotten virtual amps to work like the real thing and I been doing it since the beginning. Virtual solutions are great in a recording environment when mixing and if I was a keyboard player using midi or played midi guitar I'd be all over it but analog pickups need analog circuits to get you analog tones just like an acoustic guitar needs acoustic materials to get you acoustic tones. Its getting closer all the time but its simply not ready for the stage.

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            • #7
              The simplest method would be to buy a power head like a Crown and simply run it into a cab
              Yep!

              I attended a "modern metal" show recently with several local metal bands. The rig of choice for this type of music is an AxeFX into a Crown (or other PA type) rackmount power amp, and two 4x12 guitar cabs, preferably Mesa dual rectifier cabs.
              This space left intentionally blank.

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              • #8
                I'm not sure if it's just my computer (Microsoft Surface Pro 4, Core i7 2.2ghz, 16gb RAM, SSD storage) but I'm able to run Bias Amp and/or Bias FX with no more than a 10ms delay, which is well within the acceptable range for me.

                I've been considering the Crown power amp into 4x12 option. I typically practice on my 6505mh/112-6 or Vox VT20X, and DI with BIas for recording, but would love to simplify the whole setup by using Bias full-time (eventually I'll probably get the BIas Head, but that's a sizeable chunk of change). I wish I could justify owning an arsenal of real amps, but I move around a lot, and it's just not practical.

                I'm not too well-versed in the technical aspects of amps, which is why I've hesitated to pull the trigger on the power amp/cab option. What wattage power amp should I be looking at to push a 2 or 4 x12 cab?

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                • #9
                  I have a decent venue in my area where I've seen it done a few times, Although it didn't look any less of a hassle than hauling an amp and peddles around, In my opinion rather than simplifying things you've complicated them, Not sure exactly what it is you want to play but if you can afford it the Roland GR-55 and suitable guitar or pickup system will take 90% of the hassle out of it, Now your down to just a guitar, amp and peddle/processor, rather than hooking up a laptop to a this that and other thing, then scrolling through menu's to dial in what it is you want to do, This way everything is a toe tap away, My hands have better things to do, Plus a lot of venue owners that feature more than one band wont invite you back if you take more than a few minutes to set up, Oh my PC just crashed, Sorry everybody, Yea that should go over quite well, and good luck finding another band willing to loan you a PC, Right? Lord knows I've borrowed a few heads over the years. These days I keep a back up though

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                  • #10
                    I've decided to just wait until I can afford the Bias Head and a Mesa 2x12, rather than trying to gerry-rig it. However, for future reference, I was able to run a line from the Headphone jack on my interface into the effects return of my Peavey 6505mh, and it sounded pretty good running Bias FX.

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