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-24db Precut Sound Quality on Rockboxxed iPod?
Andhyka:
Hi, I just joined Rockbox forum being Hi-Fi newbie since I got my iPod and decent canalphone (MDR-EX90) one month ago. Â ;)
Recently, I installed Rockbox on my iPod after reading some ipod SQ posts on Head-Fi.org, and wow, Crossfeed and HW SQ are awesome! It drains battery and is bit laggy though but it's negligible.
I have a question, does massive pre-cut (-24db) have an impact on sound output? I was thinking of setting my volume to 0db (line out, cleanest quality) and use pre-cut as a volume control to handle my headphone instead. I read somewhere in the forum that input source (44khz, 16 bit) gets upscaled to 32 bit during DSP, and is downscaled back to 16bit for the DAC.
But since the output is compressed (from -24db precut), will it have the same high dynamic range as when it was not cut at all (0db precut, but @ 50-60% volume)?
Edit: I finally settled on this matter. Doing all the above steps is not recommended as it can reduce the clarity/fidelity of audio signal. Either sets the pre-cut level suitable to your headphone, or turn it off entirely.
pabouk:
Because the pre-cut is applied in the digital domain you lose the dynamic range by lowering the volume using pre-cut. This practically means that the quantization noise will be louder. If I remember it correctly 6 dB corresponds approximately to 1 bit of digital resolution thus by applying -24 dB you would have a digital resolution of 12 bits instead of the original 16 bits.
Andhyka:
Ouch, 4bit lost in translation is intolerable i presume. :o
I thought everything in digital domain will not lose detail and clarity.
pabouk:
--- Quote from: Andhyka on August 07, 2007, 06:31:57 AM ---I thought everything in digital domain will not lose detail and clarity.
--- End quote ---
This could be true only if the DA converter in your player has resolution of at least 16 + 4 = 20 bits and S/N ratio at least 120 dB!
Andhyka:
Oh well, thanks for the input. I raised this whole issue because the iPod sounds best near/at 0db (according to Rockbox & Head-Fi fellows) and is too loud for headphone, so pre-cutting in equalizer helps but at the cost of reduced/compressed clarity.
The other solution possible is adding amp (which I don't bother spending one cos it is more expensive than the headphone itself) and adding iMod (costs the same as 30GB iPod).
After tweaking little bit, I settled on this:
Volume: -15db
Balance: -3%
Pre-Cut: -9db
Crossfeed (Direct/Cross/Attenuation/Cutoff): 0db, -6db, -6db, 700hz
Hardware EQ (Bass Cutoff/Gain): 105hz/6db - turned on when crossfeed is off
Software EQ is on only for pre-cut, anything else is off.
Ideas/Suggestion/Feedback?
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