Modify BFD for non-balanced?

Discussion in 'Archived Threads 2001-2004' started by DerrickW, Mar 11, 2003.

  1. DerrickW

    DerrickW Stunt Coordinator

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    I know that the balanced inputs designed for higher voltage sources is one of the major downsides of using the BFD for subs. Has anybody considered modding this little toy to take a non-balanced source, and perhaps handle home theater level inputs better?
     
  2. Seth_L

    Seth_L Screenwriter

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    Ummm... I plugged the sub out of my reciever into the BFD and then took the BFD out into the sub amp. I know my DA5ES doesn't have balanced outputs and I'm not using balanced connectors anywhere in the system. It works fine.

    Where did you get the idea you need a balanced setup?

    Seth
     
  3. ThomasW

    ThomasW Cinematographer

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    Seth is correct, one can use standard mono 1/4" plugs (or 1/4" to RCA adaptors) into or out of the back of the Behringer
     
  4. DerrickW

    DerrickW Stunt Coordinator

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    I think that came across backwards. I thought the BFD was balanced for pro-audio. I'm talking about modding it for unbalanced home audio use. I'm guessing you did a RCA to 1/4?

    But don't we still have the signal level issue? What does the -10 or +4dB switch actually do? Several people have complained that the BFD attenuated their signal significantly. Also, unless that switch is boosting the input or changing the ADC limits, there will be considerable quantization noise from sampling the lower-level home signal.
     
  5. DerrickW

    DerrickW Stunt Coordinator

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    Seth, I know you've got an EE degree too. Are you interested in this? I've never looked at the circuitry for a balanced input, but I'd guess they use some type of differential amp at the input (low gain)? Then an A/D with limits set for pro signals. What I'm thinking is either bypassing that differential input and switching the A/D to a higher quality one with appropriate limits, OR changing the input amp gain to use the A/D fully. Does this make some sense? We could also drop in a higher quality D/A at the output too. I can't imagine appropriate parts running too much $$$, and this should improve the BFD performance. Then again, I might be guessing at the circuitry completely wrong.
     
  6. ThomasW

    ThomasW Cinematographer

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    Most 'balanced' pro-sound equipment that has 1/4" plugs can be use with standard unbalanced interconnects.

    I use Behringer and Symetrix pro-sound gear in 2 different systems and don't have balanced signals anywhere. And I have no problems with line level issues.

    Actually most pro-sound stuff (particularily the low buck products) aren't 'true' balanced (dual differential circuitry).

    Almost all the Behringer equipment uses SMD's, so it's not the easiest stuff to 'tweak'. Yes they use pretty cheap DACs, but for sub EQ it doesn't create audible problems.
     
  7. DerrickW

    DerrickW Stunt Coordinator

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    Any links or info on those SMDs?
     
  8. Seth_L

    Seth_L Screenwriter

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    I think he meant Surface Mount Devices.

    Seth
     
  9. Dave Milne

    Dave Milne Supporting Actor

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    Since it sounds like the BFD offers the option of balanced (XLR) or single-ended (1/4"), this probably isn't really an issue.

    But for someone who really wants to tear into their BFD... I think the BFD now uses 24-bit converters - perhaps something like the Burr-Brown PCM1802. This particular device has 3Vpp single-ended input. Undoubtedly there's at least one buffer amplifier to convert the XLR differential input to single-ended and apply appropriate gain or attenuation. You could go in and try to optimize... but as Thomas said, the parts are all surface-mount and it's not very easy to modify...
     

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