Bongiovi DPS

Reply To: DPS 2.0 Testing (OSX)

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Thanks for sending me the output you are hearing.  That clears things up a lot.  This is actually a fairly complex story which is why we have been having a little trouble.

First, let me clarify that we are hearing crackles on both the original file AND with the DPS Paris profile.  Take a look at the original file:


I have enhanced the spectrogram with Photoshop so you can see the high frequency lines during the power chord.  Those are most definitely artifacts in the original recording or transfer.  You can hear this if you listen carefully on studio monitors or speakers or headphones with good high frequency response.

Now this is the same passage with the DPS Paris profile as it appears on my system:


I did not enhance this image.  DPS is enhancing the high frequencies by about 15dB so you can easily see the crackles from the original recording are present in the DPS version in the same places.   DPS is just enhancing them so they are easier to hear (and see in the spectrogram).

So you can see why we felt the DPS algorithm is not at fault since enhancing any recording is the intended result of DPS.

Now this is the audio file you sent me:


Look at all those crackles!  Those are because the signal is exceeding 0dBFS which is the maximum allowed for your DAC.  So you are hearing the natural crackles AND crackles due to clipped samples.  That’s no good!

This is a very simple problem and has nothing to do with the DPS processing algorithm.  However, something is pushing the signal into the danger zone for your DAC.  That is the question we need to solve.  Since I can only look at the problem from our app’s perspective, I am going to place blame on our Volume Boost feature.  It had to be modified from 1.0.7 and could not be duplicated exactly due to changes made to our core processing library.   I also have to add Volume Boost is an OSX only feature that occurs after the DPS algorithm in the signal flow as a separate scalar function.  So there is some complexity for us to consider.

I will get with our programmer to be sure that when Volume Boost is off there is no extra make-up gain that makes any samples clip.

To help you in the short term, I added Paris -6dB profiles to Dropbox.   Please try these.  -6dB should place the output well within the headroom of your DAC.  If there are still excessive crackles (beyond the natural ones) send me a new recording.