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Originally Posted by steinba /img/forum/go_quote.gif
Could be that the CD just is a victim of the Loudness War though
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That, or they just multi-tracked it to death.
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HOLY SWEET MOTHER OF.... :-O THIS IS ABSOLUTELY, GOBSMACKINGLY AMAZING! (Just had to get that out.) |
I'm glad you like it.
Since you like Roger Waters, you may also have some Pink Floyd, much of which is also reference worthy. They recorded some of the best bass testing material available, particularly if you're not interested in electronica type bass. Delicate Sound of Thunder....yummy.
The only acoustic bass I like better for testing is disc 2 of Talking Heads'
Sand in the Vaseline.
Life During Wartime from that disc is simply amazing.
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There was a noticable hum when I touched the bare metal potmeter shaft, but I hope this will be gone when I get the pot mechanically attached to the metal case. (Confirmation, anyone?) |
A naked amp board should still be quiet if you added a ground strap to the pot. If you did and it isn't, it could indicate a ground loop. Confirm by testing with a battery-powered portable player. If that cures the hum, the problem is systemic, not something with the PPA in specific.
You might be able to cure it with a ground loop breaker in the PPA. I show one such in
this thread.
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I hope more gain (and headroom) will improve things further. |
The only way that would happen is if you have some uncommonly high dynamic range recordings, on high bit depth media. For instance, an SACD where most of the music is at like -40 dB below full scale. Virtually no real-world recordings do this, quite aside from the Loudness War issue.
Clipping isn't one of those squishy matters of audiophile opinion. If you think your amp is clipping, it's east to find out for certain. Set the volume to the correct listening level for the recording in question, then play a full-scale test tone from a test disc on the same player. (Don't have cans plugged in for this.) Measure the volts, multiply by 2.828, and see if that fits within the op-amp's output voltage limits. If it does, it can't be clipping, at least not due to insufficient voltage gain.
For instance, an OPA637 wants approximately +/-3 V between the rails and the output signal. Call it +/-3.5 V to be safe. With a 24 V supply, that leaves 17 Vp-p to play with, or almost exactly 6 Vrms. 6 Vrms into almost
any dynamic headphone is destructively loud, to your eardrums for certain and probably to the drivers, too. And at G=8, you can get a 6 V signal with a 0.75 V input signal, which isn't all that many dB off full CD line level.
I'm ignoring things like passive crossfeed filter loss here, of course.