file Question: Splitting Line Level Inputs or Outputs

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ArthurDaniels Posted 4 weeks 1 day ago
#27283
Hi Gang:

Here is a question about splitting Audio Line-Level Inputs or Outputs: I am considering splitting a Line Level Output from one of my amplifiers in order to provide inputs to two other amplifiers. I have made these type of connections in the past with no noticeable effect.

I understand that the impedance levels are relatively high for Line-Level inputs and outputs, so loading is potentially not as much of an issue as with lower-level-impedance situations. Nonetheless, I would be interested in comments from any of you who are more knowledgeable than I am about what I propose to do.

Thanks,

Art
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Moderator Posted 4 weeks 18 hours ago
#27287

ArthurDaniels wrote: Hi Gang:

Here is a question about splitting Audio Line-Level Inputs or Outputs: I am considering splitting a Line Level Output from one of my amplifiers in order to provide inputs to two other amplifiers. I have made these type of connections in the past with no noticeable effect.

I understand that the impedance levels are relatively high for Line-Level inputs and outputs, so loading is potentially not as much of an issue as with lower-level-impedance situations. Nonetheless, I would be interested in comments from any of you who are more knowledgeable than I am about what I propose to do.

Thanks,

Art


Art, give it a try and see what you think!

For the technical aspect, my fuzzy memory recalls that minimum input impedance you're trying to drive should be 10x or more of the output impedance of the source. I heard from a well-known designer once that he felt 50x was better. So, if your source has an output impedance of, say, 1000 ohms, the overall input impedance of the device you're driving should be 10k ohms or more, maybe even 50k ohms.

For splitting, you can calculate the input impedance your source will see. If you're splitting three ways, the formula is 1/Rt = 1/R1 + 1/R2 + 1/R3. "Rt" is total resistance. Just add or subtract another "R" for how many splits you have. Using the three way split here and let's assume each split has a 50k ohm input impedance, you have 1/Rt = 1/50000 + 1/50000 + 1/50000 = 0.00006. Solving for 1/Rt you have 1/0.00006 = 16,667 ohms overall input impedance.

I hope I remembered my math correctly...

Again, try it and see what you think!
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ArthurDaniels Posted 4 weeks 13 hours ago
#27289
Hi Mr. Moderator:

Thanks for supplying the formula.

In my case, I am splitting the Line Output from my Cambridge 851A into two inputs - one for my Cambridge 120 Receiver and one for my Sony STR DE 885 Receiver. The respective input impedances are 47K and 50K.

Using the formula, the resultant Input Impedance load is 24.227K. Should not be a problem for either device, so I have made the physical connections and I am listening to various tracks as I type this message.

Thus far, I have not detected any audible differences and I believe the resultant impedance load is high enough to not cause any issues with either the Cambridge or Sony units.

Using this connection scheme allows me to operate either the Cambridge 120 or the Sony 885 independently, which means that I can add additional sound to widen my sound stage via the 120, or add augmented bass via the 885.

Currently, I am driving my Ones as Fronts from my Cambridge 851 Stereo Amp, my Sevens as "Side Fronts" and my Sat 3Cs as Front Heights from my Cambridge 120. The Sony is providing augmented bass from the LFE output to the Ones LFE input.

Again, thanks for the help. I am really enjoying my setup and my GE speaker array.

Art
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Moderator Posted 4 weeks 13 hours ago
#27290
Sounds great and 24k input impedance should be fine with no issue at all. Now kick back and enjoy!

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