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Where does the LINEOUT signal come from in the amp chain?

Discussion in 'Recording' started by GirlsCanRock, Jun 29, 2005.

  1. GirlsCanRock

    GirlsCanRock Guest

    working on my "stage computer" setup as described in ProAudio (and duely ignored...). Have an old practice amp (several) with a LINE OUT.
    Where exactly in the chain is that signal coming from? Is it out at LineLevel?
    real question is this- can i use the amp as a simple clean PREAMP before I send it to my soundcard from the LineOut?

    My gtrs are BOTH in the shop, so I can't even test this out.

  2. pr0gr4m

    pr0gr4m Well-Known Member

    Just a guess but I would say that the line out is post distortion/eq//whatever but pre amplification. So yes. You should be able to go out of that into the computer.
  3. Sheffy

    Sheffy Guest

    "Most" line outs are just that - line out. They may or not be referenced to 1.0 or 1.25 volts. The bigger question that needs to be addressed with a setup like this is whether your connection will create "microphonic ground loops." This is the annoying buzz/hum that occurs between gear of different manufacturers. If you are not isolating the signal (amp) from the sound card, you will likely have this problem. You might have limited success eliminating this with an inexpensive mixer or an isolation transformer. Again, you won't know until you make the connections. Start off with the line level down and see what noise, if any you hear. From there, start increasing the gain (level). Finally connect your guitar and see what you get. Good luck. As for "clean," that's a whole other issue. What ever you end up with, you will want the find a happy medium between singal-to-noise ratios and overdriving your sound card.

    Is there a reason that you don't want to mic the cabinet for a more natural sound?
  4. McCheese

    McCheese Well-Known Member

    Usually it tells you in the amp manual where in the chain the line out comes from. For instance in my amp it's post drive section, but pre 'verb. Just make sure you're still driving speakers or some other load bearing device or you can blow your output transformer (especially with tube amps). There should be more info on this in your amp's manual as well.
  5. voidar

    voidar Guest

    My amps line-out is post output transformer.
  6. anonymous

    anonymous Guests


    Most are post transformer. Like voidar said. But, some have a pre/post switch. Check to make sure your does or does not have one. My ampeg pre-amp does. However, you shouldn't have a problem with using it as you described. Good luck
  7. GirlsCanRock

    GirlsCanRock Guest

    just to rehash-
    I'm using GuitarRig and/or my POD thru the PA. I have a stage monitor to hear it, but I want an AMP on stage. Other guitar player has one, so I can't just be thru the PA. ROCK GUITAR comes from the stage :!:
    So one output goes to the house, and then one to this "AMP" I'm working on. Probably just a 10" woofer and a piezo tweeter with a pad on it; driven by a 100w power amp.
    If I use Guitar Rig, I'll need my PC on stage, which is too nerdy. So I'm building a cabinet for it. The cabinet will look like an AMP. Probably a '59 Bassman. It will also house a preamp (hence my question) and carry the custom pedalboard I have in the works (super sweet, controls everything in GRig and has 'virtual pedals').

    I'll then just add what looks like a small Marshall BluesBreaker that has a power amp and some speakers in it. This will also be used to push some of my acoustic guitar off the stage too.

    follow all that?

    Oh- I have rackmounted preamps and compressors in my basement 'studio' (its not really), but I'd rather just have a preamp already in the computer box and ready to go. If I use the POD, then I'll just have to haul around the "BluesBreaker" power amp.

    Either way, if I didn't use a POD or CPU, I'd be hauling 2 amps around. And this way has much more versatiltiy.
    Oh, and looks cool as S 8)

    In progress.....
  8. moonbaby

    moonbaby Mmmmmm Well-Known Member

    "Most are post-transformer"? On a guitar amp? A bass amp? Most lineouts on a guitar amp are somewhere between the preamp and the power amp section, regardless of whether they are tube or SS. This would place the ouput AHEAD of the output transformer(which is not even exisitent on a solid-state amp).Some "boutique" amps like the Kendricks (and THD) use a post-output transformer circuit to emulate the "EMF kick-back" that the speakers would normally provide. Very few bass amps utilize a real tube output section, these days, hence the total absence of an output transformer to tap off. (Yes, I know that there are the exceptions, like the ORIGINAL SVT, some of the Sunn/Fenders, and Mesa rigs). I would hazard a guess that the Line Out on a Bluesbreaker is ahead of the power amp section, not after the output transformer (at least that's where it is on my JCM800 and "new" Plexi models). Guitar amp manufacturers do not typically devote much time or $$ to that aspect of the amp. I would offer up that you would be well-advised to purchase a decent DI box to use with these line outs. A good DI will offer a ground loop "lift" function to fight the problems that Sheffy mentioned earlier. Many offer a filter to emulate the tonal response of a speaker cab. I use a POD into a Bandmaster Reverb head, and even then, I use a Whirlwind DI to quiet things down...THEN I MIKE THE CAB!!!! Get an SM-57 and rock,baby!!PEACE. :)
  9. Tommy P.

    Tommy P. Well-Known Member

    GirlsCanRock, I saw your other post about a broadband amp...Atomic amps supposedly makes a good broadband amp for modelers, but I havn't used it. That 10" speaker you want to use is an OK choice, decent but not great efficiency 92db . . The 12" Eminence legend modeling speaker might be a better choice though, because it has an efficiency of 101db. Huge real world difference there. Weberspeakers.com has it for $44.00 The 100watt solid state amp should be fine for a low stage volume.
    I used to use a J-Station into a Crown 500w/channel into eight-eight inch speakers in four arrays that covered very well.

    As far as line-outs go, its all of the above that were mentioned.

    Most line outs are from the preamp, not the power amp. In this case, you'll get tone from the pre's tone stack and distortion, not the power amp. For example, the Fender Hot Rod Deville has a pre-out(part of the effects loop), but the reverb and presence control are post, and don't affect it. You can get line out from any effects loop.

    Now then, if you want to have the powertube distortion as part of the tone, then a device like the Weber mass or mini-mass is what you want. Its very similar to what is included on some boutique amps except for the fact it has a real dummy speaker driver acting in a real world situation as dummy load(as opposed to others that are just resistive loads)..
  10. GirlsCanRock

    GirlsCanRock Guest

    I had no idea that that speaker even existed.
    Thanks a bunch for the info.

    I want to keep the signal as clean as possible INTO and OUT OF the modeler/cpu.

    To Clarify- There is NO real amp here. No BluesBreaker. No '59 Bassman 10. Its all just for looks. I'm magic with a table saw and mail order tweed.... :lol:

    Biggest challenge is a small yet useable screen for computer applications on stage. 7" LCD would be cool, but I'd rather put the $ into a power amp and speaker. I have a TV out of the DAW, so maybe i'll just use a small portable TV. All I really need it for is to set up the program.
    At least at this point. Down the road I want a nice fat LCD screen. And I have a rack mount case from and old APC Power backup. Will convert it to a rackmount PC. Sweetness. Rack a preamp compressor above it. My A/D converters somewhere in between.

    I'd like to run my acoustic thru this amplifier too, so I'd like a piezo tweeter in there too. Do you see any reason this is a bad idea? I figure it would be just like any other PA speaker.

    Getting really excited about this project.
  11. Tommy P.

    Tommy P. Well-Known Member

    Heres a link to Weber. http://www.tedweber.com/ The best prices on Eminence speakers on the net (add to cart to see the real price), plus other great products. Here's a link to Avatar speakers http://www.avatarspeakers.com/, also great prices and service. I have no connection or interest whatsoever in Weber or Avatar, I'm passing along this info for the sake of members here.

    The piezo is a good idea for a modeling rig, but they do tend to burnup easily. Also when you tweak your presets, try and do it at full stage volume in a rehearsal situation. Tweaking at bedroom or headphone volumes will cause you to run for your tone controls when the Fletcher-Munson curve catches up to you in a live stage mix.

    If you can get a computer rig to behave in a live situation, it should be a lot of fun.
  12. moonbaby

    moonbaby Mmmmmm Well-Known Member

    A girl who rocks AND is a whiz with a tablesaw and tweed.....I think I'm in love! Be careful with using a piezo on the guitar amp...some amps don't like them as a load and will eventually lose an output device (i.e., dead transistor=no sound). Plus, they sound kinda harsh on acoustics and tend to exaggerate string noise,etc. You might look at a Foster horn (I see that Carvin sells these on their website). These are passively crossed over (they have the x-over,too), so they aren't such a problem on the amp. They are very popular among bass players for their smoother top end,and that should play the same for your acoustic. The Eminence Legend is a great choice, by the way. I rebuild tube amps and find those to be much cleaner, louder, and smoother than any of the "vintage" Jensens and the like.
  13. pr0gr4m

    pr0gr4m Well-Known Member

    In my opinion, there aren't enough nerdy guitarists.

    Robert Fripps of the world, UNITE!
  14. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Fripp rules! I finally got a CD of "Larks Tongue and Aspic"...how old am I? Using a laptop onstage is COOL, baby! Let it go! I just got back from an electronic music convention up in Philly and there was no shortage of "nerds" making noise. Some were looping loops on loops, others were using virtual synths. I use a laptop to use B4 (a virtual Hammond B-3) and Arturia Modular V (synth) programs.
    GCR... with a laptop, no less!

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