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Can I plug direct from my amp to interface?

Discussion in 'Recording' started by SunDaze, Mar 27, 2011.

  1. SunDaze

    SunDaze Active Member

    Hi guys ,
    I have a Blues Junior amp that does not have a line out .
    It only has speaker and ext speaker outputs.

    Im wondering if I could plug from the main speaker output straight to the 002 rack
    with a lead that has a 10 db attenuator ( A tech made the lead when I used to take
    audio from the desk to a video camera ).
    We recently moved to a townhouse type setup and there is no way I can
    mic my amp to record. Ive looked on billm s site but he doesnt have instruction
    on where to take a line out from.

    Has anyone had this problem and how to get around it without spending money ...lol
    Also will I do damage to the amp by doing this?.
  2. TheJackAttack

    TheJackAttack Distinguished Member

    You won't damage youramp but you will damage the 002 if you don't pad enough. I'd start with at least a 30dB pad if I had to do it. Amp levels aremuch hotter than line level. Link or someone might have an idea where you could wire in a line out.
  3. dvdhawk

    dvdhawk Well-Known Member

    I agree with Jack, 10dB isn't going to be enough. Plus the smallish transformer you'll likely find inside a 10dB pad may not be rugged enough to put up with that much wattage without distorting, warming up, or burning out. The windings are probably a pretty fine gauge of wire on a 10dB attenuator.

    There are DI boxes made just for your job, such as the Whirlwind Director which isn't too horribly expensive. Rapco / Horizon makes a Speaker Level Direct Box ( SPL-1 ) which is probably slightly less expensive. (I'd add links, but I wouldn't know where to start shopping for musical gear in Aus. )

    Anything of that nature will do, but regardless of how you bypass the speaker you'll lose some of the Blues Junior's cool signature sound.
  4. SunDaze

    SunDaze Active Member

    thanks for the replies Jack and Hawk . I really appreciate the genuine quality of advice hear from people that know what theyre talkin bout !.

    So what if I went for 40 db or 50 db?
    I m gonna try and hunt down the drawing for the 10db attenuator now
  5. SunDaze

    SunDaze Active Member

    mmmm , cant find it , damn it.
    I know its like maybe 5 resistors and should be easy to do if I had the right value resistors and the drawing.
    If you have been down this road , can someone point me in the right direction , because Im so over sifting through all the $*^t on the net to get
    to the right place.
    spending more than 10 bucks is not fair cause I just spent money on some kinman pick ups and we are doin busking in a new town at the moment
    cause we lost our work due to a cyclone ( get the violins out hahaha ) .
  6. TheJackAttack

    TheJackAttack Distinguished Member

    A 10dB pad just isn't going to do you any good whatsoever. I know I stated start with a 30dB pad but even that is going to be on the low end of what you want very likely.
  7. TheJackAttack

    TheJackAttack Distinguished Member

    Uneeda Audio - Build your own attenuator pads

    I make no claim to the efficacy of this website. It was just the first google hit for "specification line level pad".
  8. SunDaze

    SunDaze Active Member

    So is it worth persuing this or am I heading upstream without a paddle?
  9. SunDaze

    SunDaze Active Member

    cool Jack ,thanxs , Im checking it out now
  10. SunDaze

    SunDaze Active Member

    Yep I its too involved for me , Im not sure what sort of voltage is comming out of the speaker wire for starter, THink I,ll leave it in the too hard basket for now.
    The pad they talking of is for a mic that is too hot going to the desk , which is what I have already.
  11. TheJackAttack

    TheJackAttack Distinguished Member

    You can purchase those pads from Whirlwind (XLR) in 10dB, 20dB, 30dB and 40dB. I think you should check out that Rapco SPL-1 or just get a pair of the Whirlwind Imp 40dB pads. If you have to save up, that is probably still the best option. Now that I have said this however.......

    Have you called up 7th Circle Audio? They're in your neck of the woods relatively speaking. 7th Circle Audio. Even if they don't make what you want they might be convinced to build you a box or direct you to another DIY local that could help you out. It really isn't hard to do if you have the math correct for your particular application.
  12. SunDaze

    SunDaze Active Member

    thanx again Jack , Ive got enough to go with for now. Found an old DI box that we never use and could come in handy once I sort out the math for the resistors.
  13. Boswell

    Boswell Moderator Distinguished Member

    You have to regard the speaker terminals of the guitar amplifier as a differential voltage source, and should not connect them to the 002 interface via a conventional unbalanced attenuator. If you use an unbalanced connection, the ground will give you all sorts of trouble, as there could well be amps of current trying to find its way to mains earth down that lead. Additionally, several makes of guitar amplifier use H-bridge drives, where both speaker terminals are driven (antiphase) to get 4 times the output power from the same supply voltages.

    You can avoid this particular problem by using a balanced attenuator and going into a balanced input on the 002 using a 2-wire plus screen cable. Wire the attenuator output to an 002 line input using standard TRS leads. For the attenuator input cable, take the ground (cable screen) to the guitar jack sleeve, not to the speaker. Connect the two inner wires to the speaker terminals.

    As the others have said, a standard DI box is no use for this job, as the active ones are the wrong way round and the passive (transformer) ones will saturate magnetically and could burn out when fed the guitar amp's speaker voltage. What you really need is a re-amp box, for which the cable and balanced attenuator described above is a poor substitute.
  14. SunDaze

    SunDaze Active Member

    AAhh ,mmmm , ok
    Looks like its not gonna happen then , cheers Boswell.
    I will plug the guitar straight to the interface and if need be ,go to another location
    later and re record it through the amp.
  15. BobRogers

    BobRogers Well-Known Member

    What is your goal here? Are you trying to record silently? Is this late night recording or are you trying to avoid bleed?
  16. SunDaze

    SunDaze Active Member

    Im wanting to record at any time 24/ 7 when I feel in a good mood for it , silently because of the neighbours and my wife also wont
    appreciate getting woken up.
  17. TheJackAttack

    TheJackAttack Distinguished Member

    Well, there is no benefit to going through the amp at all if silence is your goal since he speaker itself is what gives it it's sound. Send it direct to your interface and monitor from the interface headphone amp.
  18. jkchuma

    jkchuma Active Member

    Here is a DI box made specifically to do what your asking.

    Radial Engineering R800 1400 JDX Active Class-A Reactive Speaker
  19. dvdhawk

    dvdhawk Well-Known Member

    I recommended a couple less expensive versions in my first reply. Unfortunately, he has a $10 budget - as he's been displaced by the hurricanes and subsequent flooding that have hit Australia so hard.

    Given your situation SunDaze, I've got an old Rapco here I'd give you, if we can find a way to ship it around the world for a reasonable price.
  20. Voiceofallanger

    Voiceofallanger Active Member

    This sounds like dangerous tricky business. I personally would avoid it :D

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