Attenuation from speaker level to line level balanced

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delapoer

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Joined 2004
I would like to generate line level outputs, for driving active speakers, from speaker level outputs. I have the added complication of the active speaker input being balanced. I think a 20dB attenuator might be about right normally but going from unbalanced to balanced (by grounding the -ve balanced speaker input) will also affect the attenuation. Can anyone throw some light on this for me? And also suggest some suitable resistor values for the potential divider?
 
PRR

PRR

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Joined 2003
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How much money and time must be spent?

I put your thread topic in Google, Images, and hit reasonable looking plan. It uses a transformer, which is a universal solution to unusual problems; I would not start there for a home system (opposed to a radio network or a 13 storey studio complex). A good "balanced" input eats unbalanced fine. 10k in each leg ensures no ground-short power faults even with bridge output. The "200r" can be adjusted on test to get the required attenuation (20dB is a good guess but probably not the final answer; and as you say, details of "balanced" give 6dB uncertainty best cured by test).
 

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delapoer

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Joined 2004
Thanks for your help. This does seem like a good idea but is a suitable Tx easily available. I did have in mind a simple potential divider, is there much to be gained by adding the Tx? Maybe just trying a variable pot to get the correct ratio would be a good idea?
 
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delapoer

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Joined 2004
I have found that there are pro audio DI boxes which can take high impedance inputs from instruments and also loudspeaker outputs before changing them to balanced XLR connections. At least one has switchable attenuation 0, 20 or 40 dB. It could probably be easily modified for other attenuations. The drawback is that it needs a 9V battery but a power supply would be easy to wire in. That might do the job.
 
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jaddie

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Joined 2011
delapoer said:
I have found that there are pro audio DI boxes which can take high impedance inputs from instruments and also loudspeaker outputs before changing them to balanced XLR connections. At least one has switchable attenuation 0, 20 or 40 dB. It could probably be easily modified for other attenuations. The drawback is that it needs a 9V battery but a power supply would be easy to wire in. That might do the job.
Click to expand...

So get the passive version.
 
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delapoer

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Joined 2004
Something else was brought to my attention on this subject. It appears that most modern AV amps have Class D power amps, and that these amps usually work in bridge mode - in a way they are already differential outputs (the negative is not connected to ground).
 
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jaddie

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Joined 2011
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