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Bypassing interface preamps

Discussion in 'Preamps / Channel Strips' started by patrick_like_static, Jan 24, 2007.

  1. Apologies. I remember reading a query about this months ago but I couldn't find it through searches:

    I'm trying to use a GT The Brick preamp with my Alesis io|26 interface and entirely (at least as much is possible) bypass the inboard pres, but Groove Tubes and Alesis have given me differing opinions as to how I should go about this. The interface has XLR/quarter-inch combo inputs with mic/guitar switches, and each channel features a quarter-inch "Insert" connector.

    I'd like to know the most effective way to get an untarnished signal from The Brick to my computer. Any help will be appreciated.
     
  2. Kev

    Kev Well-Known Member

    use one of the line level inputs

    the Alesis I/O26
    Line gain range: -15.4dB to 27.8dB
    Line impedance: 16kOhm

    I can't see if it is balanced or unbalanced

    the GT Brick
    Output Level
    Nominal + 4 dBm
    Maximum +16 dBm
    terminated at 600 Ohms

    " The Brick will preamplify any line or instrument signals directly into a +4 or -10 Line input stage of your mixer or recorder. "

    for balanced to balanced - no problem
    just give the Brick a load ... 600 ohms to 1K ohms

    if it is unbalanced ... use pins 2 and 3 with the load above 600 to 1K and wire a 6.5mm unbalanced

    try with and without the shield on pin 3
     
  3. Mises

    Mises Guest

    I dont have the schematics for that particular Alesis model, but your either going to have to forget your idea, or do some modifying.

    Chances are very likely, that the line inputs are connected to the preamp circuit. I assume you know this, which is basically why your asking this question to begin with.

    This is the way it is in the overwhelming majority of gear is, including even the better mixing boards, and it is completely asinine in my opinion to ever put a line input attached to an amplifier circuit without a hard bypass switch... but nonetheless... thats the way it is.

    You cant make the line input a true clean line input without knowing what your doing. You'll need to get hold of the schematics from Alesis... and modify at least one or two channels yourself to bypass the amplification circuit.

    I work on and modify a lot of Alesis units myself and they tend to use integrated circuits ("chips") up the rear end in almost all of their units, so the modification is somewhat delicate and requires above average soldering skills... a lot harder than working with discrete, non-IC components.
     
  4. RemyRAD

    RemyRAD Guest

    You are going beyond reasonable thought, in your bypass fantasies.

    There's just no real reason to bypass all that stuff in your Alesis mixer I/O. I mean if it sounds that bad to you, why would you want to feed anything else through it? I would recommend throwing it out into the trash if you feel that strongly? But that's ridiculous. I'm sure you find it more than adequate for all of your other input needs? And you should because there is only so many integrated circuit chip manufacturers and you can only arrange them in so many ways and so, your mixer isn't much different than all of the other comparably priced mixers like it. And your recordings will only be as good as your technique and not whether you bypassed an integrated circuit chip or 2.

    You get the character of the sound from the microphone preamp so take your Brick and patch that into the Alesis insert return on the channel input of your choice. You will go on to make glorious sounding recordings and nobody will be the wiser that you fed some signals through that horrible sounding Alesis mixer you should have never purchased. I promise, we won't tell anybody.

    I mean if you want a real bypass? See a cardiologist.
    Ms. Remy Ann David
     
  5. I appreciate the help, guys. To clarify: the Alesis unit is just an interface, not a mixer, and much as I'd like to be handy enough to modify it the most frugal solution is going to be to return something while I still can. In using the mic pre on The Brick, the only output available is the balanced XLR. Is it possible to I could run an XLR-to-TS cable from The Brick to the Insert connector on the interface? The schematic shows this as bypassing the preamp but I'd like to know whether this is a viable option.
     
  6. Kev

    Kev Well-Known Member

    :?
    I though that's what I had suggested with the comment above
    Make a simple cable with a female XL3 at one end
    pin 2 = hot = the hotest colour wire ... like red or white
    pin 3 = cold = coldest colour wire ... like black or blue
    pin 1 = shield = ... shield .. the braid or the drail wire that touches the foil

    between pin 2 and 3 use the 600 to 1k resistor to provide a load for the Brick output transformer
    this is an area you could experiment with as you may like high imp or no resistor at, all while others may like below 1k


    at the other end .. buy a 6.5mm Tip Ring Sleeve .. TRS connector

    you now can try all options until you find the one that offers the lowest noise floor.

    see the Rane library for all the options
    http://www.rane.com/library.html

    http://www.rane.com/note110.html
    make it as if it were cable number 3 but mod it to 5 or perhaps 3

    IF you use the insert return then you will probably need to use the Ring as the input.

    does this make sense ?
     
  7. RemyRAD

    RemyRAD Guest

    Well patrick_like_static, you're not making much sense here. Your Alesis product is akin to the Mackie Onyx products. They are touting their higher sampling rate and bit rate, along with their superior Cirrus brand analog to digital and digital to analog converters. This is a complete computer interface that offers really nice specifications. You might like your Brick, but it's not a computer audio interface. It's merely a preamp. Want to use it, you need to plug it into an analog-to-digital converter which will provide you with all of a single channel. And so you feel that is better than 8 channels??

    So you also, seem to be stifled by not being able to make a good recording with your Alesis? And so you think you need the Brick to make good recording? I think you are confused and inexperienced? And so, it appears that with or without your Brick, your Alesis interface seems to be only capable of 8 simultaneous inputs? I assume you feel that is not enough inputs for your needs?

    What I also rather funny is that it claims to be a 24-bit, 192kHz device but its specifications reflect that more of a 16-bit system than a 24-bit system. So, go figure?

    Some people may even think that being constipated is a good thing? Since you've still have obvious nutrients in your body. Why would you want to get rid of that? I can't possibly think of what advantage there would be to expulsion? Then you would have at least one item less in your possession. Is that a good thing? I don't think so?

    Constipated opinions that I just can't get out.
    Ms. Remy Ann David
     
  8. Okay. Thanks a lot, Kev. Sorry I didn't catch what you were saying the first time around. Those links you sent me were helpful.

    Inexperienced in this scenario, yes. My endeavors in all this were not to sell or outmode my Alesis but rather to have one standout mic channel to use with my interface instead of the included 8 bottom-of-the-rung pres.
     
  9. RemyRAD

    RemyRAD Guest

    patrick_like_static, "bottom of the rung microphone preamps"? I don't think so. What makes you think that those microphone preamps are inferior? They are touted as being boutique quality and I'm sure they are. There are so many excellent microphone preamp chips now available that were not available just a few years ago. So your substandard interface is probably no more substandard than any other substandard interface like Presonus, Mackie, Allen & Heath, Focusrite, et al.. Your Brick, really won't make much difference if your engineering chops are not up to snuff to begin with. Which sounds like the problem you are currently having if you can't make a good recording with those 8 lousy microphone preamps? I mean if you need better sound? Better get rid of that Alesis and purchase yourself a bunch of Apogee or Pyramix converters and be done with playing with toys.

    I make great recordings with lousy microphone preamps. What do you make of that? It's certainly not the preamps but my technique, experience and expertise.

    Now go back to the corner and sit there for a while and think about this. Nobody had boutique preamps 20 years ago. All of those songs sounded like crap! Didn't they? OF COURSE NOT! THEY SOUND FABULOUS! Most of that stuff was recorded with the equipment du jour that did not necessarily have fabulous state of the art specs.

    You need to learn how to make good recordings with compromised equipment before you can make good recordings with good equipment. It's not the equipment, it's the engineering.

    It's not a tumor!
    Ms. Remy Ann David
     
  10. I never said I was unhappy with my results. Just that, in terms of price, 50 bucks a channel (i.e. my Alesis unit) is pretty low grade for commercial purposes. Your comments are noted, though.
     
  11. RemyRAD

    RemyRAD Guest

    If this had been 20 years ago, I would say a $50 microphone preamp would probably sound like crap? But today, if you think about it, there are so many new and fabulous integrated circuit chips that are certainly beginning to outperform the older classic discrete operational amplifiers like the API and Neve. They only cost a couple of dollars apiece! And so a nice boutique quality microphone preamp might consist of a superior microphone preamp chip. The output of that chip may then feed a couple of more chips for proper output drive and balancing with a possible servo chip, to keep DC offsets, eliminated or, greatly reduced. Just because they are not using expensive, old-fashioned transformers, doesn't mean that those microphone preamps should sound bad. They probably sound quite good. Amazingly good. So I wouldn't discount their possible quality?

    To secure your beliefs, might I recommend that you either purchase or build your self an XLR "Y" cable adapter. Plug your favorite microphone into one end and plug the other 2 ends, one into your Brick and one into the Alesis. Of course the output of the Brick, will most likely have to be plugged into one of the Alesis' line inputs. Record to 2 tracks simultaneously and then play back that track switching from one channel to the other channel. I think you will certainly hear a difference but you have to evaluate whether that difference is important to you and what it means?

    I don't usually indicate when a microphone preamp is good or bad. I just try to evaluate what that preamp might sound best on? Not whether it's bad sounding or good sounding. Good or bad, you have a greater palette of color to work with.

    Always colorful
    Ms. Remy Ann David
     
  12. aqualand666

    aqualand666 Guest

    you have the right idea, you do want to bypass your interface's preamps. i highly doubt that they are as good as mackie's XDR or focusrite pre's. compared to that GT piece of $*^t they might be though. you are still going to experience the noise ratio of your interface by going into any analog input on it, but obviously that isn't as big of a deal as bypassing the preamps.

    the preamp is just a little attenuator, to bypass you just put it at zero.
     
  13. hueseph

    hueseph Well-Known Member

    I'm sorry but that is classic liquity split. You go aqua. :)
     
  14. aqualand666

    aqualand666 Guest

    i don't understand your god damn canadian jargin you fuckin canuck
     
  15. hueseph

    hueseph Well-Known Member

    Again with the liquid commentary! Is it possible there are two? I don't know. If so, your doppleganger was here a few months ago.
     
  16. RemyRAD

    RemyRAD Guest

    Now now, I'm not Canadian, but I could be. You really weren't talking to me, I know? I was raised in Detroit, at Motown and used to go into Windsor all the time. Hey, you talkin' to me? You talkin' to me?

    I think you're really vastly mistaking the fact you really aren't bypassing any preamps, in that little interface, by plugging your boutique microphone preamp into virtually any audio interface. Putting an attenuator in front of your microphone preamp gives you a microphone preamp with an attenuator. Going into the line input simply put you into their other cheap integrated circuit chip line inputs. It's the same crap. Now if you really want a good sound, you would plug your API or Neve microphone preamp/EQ into your Apogee converter. Now that's a quality signal path that costs a few $$. So you get what you pay for, generally. If you put a Ferrari engine into a Chevy Impala, you have a Chevy Impala that makes lots more noise. Not a Ferrari.

    For better sound, you probably want to avoid recording anything? If you don't record anything, you'll have no problems with signal-to-noise ratio or bad preamps. It would be much better if you just learned how to sing or play an instrument instead? After all, you still need to make a living and unlike myself, it probably won't be an audio?

    Snobby great engineer
    Ms. Remy Ann David
     
  17. Kev

    Kev Well-Known Member

    insert point
    yes it probably is unbalanced

    and it should bypass ... their other cheap integrated circuit chip line inputs
     
  18. The only good results I've gotten are by going XLR female from The Brick to 1/4" TRS into the Alesis' combo connectors. There's some noticeable noise in using this method, but The Brick's characteristics are much more favorably apparent than by the other three techniques. I'm pleased with it.
     
  19. Mises

    Mises Guest

    Yeah. "Take off", you Canadian hoser.

    Like we dont understand your whacky Great White North slang down here in 'the states', eh.

    What aboot what you were telling me the other day... You known, aboot the thing... remember. That was a beauty, eh?

    Now, go eat some back bacon, drink a "two-four" of beer, and go to a hockey game.

    :wink:

    I love taunting Canadians based on americans sterotypical perceptions of Canadians thanks to these guys:

    B000001EPF.01._AA240_SCLZZZZZZZ_.jpg
     
  20. hueseph

    hueseph Well-Known Member

    Dood. Unfortunately that is a Canadian's interpretation of Canadians! No kidding eh! Rick Morranis and ...uh...the other guy are both Canadians. So I suppose were best at making fun of ourselves.

    As my great great grandfather Low Flying Eagle Schlong would say "haiuk tuk shinook saskachewan" which in our language means"Wife! Get me a beer!".

    There was another movie called "Canadian Bacon" about a bunch of canadians who were thought to be invading america. All the actors were Canucks. Go figure. A lot of the cast and crew of SNL have been Canadians over the years as well.

    By the way Mises. Do a search and read up on aqualand666 and while your at it search liquidstudios and you will fully understand what I'm talking about.
     

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