The Dark Storm is near.

I've been playing around with some final tweaks to the Dark Storm design.  I want it to be flawless and kicking  ass right out of the starting gate.  Yesterday I very slightly improved its already impressive frequency response, S/N ratio, and THD.  But, not all was a success.  I have been trying to create a circuit that illuminates a single LED when audio is present.  I've done that, but not while also meeting the design requirements.  The requirements are that it can have no affect (0%) on the THD of the Dark Storm's audio, that it can not affect the total gain (dB) of the Dark Storm in any way whatsoever, and lastly - all of the components used in the circuit must be currently in production and available.  If you know of a circuit that meets these requirements, please educate me.  I'll gladly pay you for your time and knowledge. 
My best attempt:  I opted for a discrete design because it appeared simpler and less expensive to pull off than a digital design.  I initially wanted to be able to monitor the incoming signal before it hits the pre.  Of the many designs I tried, the best one worked best when monitoring the output of the Dark Storm.  Regardless, this design failed because it adds 0.09% THD to the signal.  I don't want distortion coming from diodes and transistors that are not directly related to the audio circuit.  Unless some wiser individual can turn me hip to a solution, I'll need to just abandon the idea of a signal indicator.  I think with any sort of analog metering, such as a VU or bar meter, I'll face the same outcome.  The Dark Storm sounds so good right now that I don't want to obscure it in any way.  I think a digital solution could work, but probably would introduce some degree of digital noise, not to mention it would probably add a fair bit to the parts bill.  Ultimately, is it really necessary to have a signal present indicator when we have DAW's with metering?