Audacity Forum

gd0 wrote:I trashed my test files, so no precise measurement. There was a visible signal, which looks like it would take about 9dB of amplification to get "right."

Given that we generally recommend recording with a peak level of around -6 dB (for 16-bit recording), the recording level sounds as if it is not far off "ideal".

The dynamic range of 24 bit audio greatly exceeds the "usable" dynamic range of either the analog components in your system or the room in which you are listening (assuming that you don't live in an underground bunker). The major benefit of 24 bit recording is that this massive amount of dynamic range means that it is not necessary to push the levels up to the limit. It does not surprise me that a 24-bit recording has a few dB of headroom.

gd0 wrote:It's starting to look like the simplest solution will be to add the analog pre-amp into the chain.

Probably not. Amplifying digitally will be both more accurate and less noisy than adding more analog components to the chain. Assuming that you use the default 32-bit float format in Audacity (recommended), digital amplification will be accurate to approximately 0.0000000000001 % (much better than the best analog equipment).

steve wrote:Probably not. Amplifying digitally will be both more accurate and less noisy than adding more analog components to the chain.

I guess. But in the case of SACD or vinyl, it's analog to start with, and once it gets played thru analog gear, background noise levels aren't discernible. Or at least not here, anyway.

I acknowledge all your talking points, Steve. We're dealing in tiny nuances with hi-res as far as I'm concerned. I'm underwhelmed with SACD, and hope to never buy another one. (Except for 5.1 surround ) I buy for content, not format.

Meanwhile, for the couple dozen SACDs I have, I feel compelled to squeeze what I can out of them for the server. Even if the difference is negligible. I do have a couple titles that sound discernibly better on the SACD layer than the Redbook layer. But even then, it's not a night-and-day difference. It could be simply the disc mastering. the human factor.

I might spend small money on a long cable to the old iMac – if I can ever figure out what that exact plug size is (really hard to research that for some reason) – and do a comparo.

Thanx again.

For 9 dB at 24 bit, I wouldn't even bother. It's a safe distance from digital clipping. And amplifying it digitally would add little to the noise floor.

I'd even bet using the built-in 3,5 mm analog jack would be worse over a longer cable.

And I always wonder why nobody uses the optical sp/dif in that plug. Is is too hidden? Is it the custom Apple plug?

As far as I'm concerned, it's the best way to connect any laptop since it is the only way that provides perfect electrical isolation. No ground loops, ever.

cyrano wrote:And I always wonder why nobody uses the optical sp/dif in that plug. Is is too hidden? Is it the custom Apple plug?

There is no transmission of SACD/DSD signals over optical (or coax digital). Only analog. (Or HDMI to a specialized DAC that can handle it.) For server/archiving purposes, SACD = vinyl.

There is a way to rip SACD digitally, but it is very complicated, and involves arcane hardware, and modification thereof.

Otherwise, I appreciate your feedback re: amplifying and the long analog cable.

I've got some experimenting ahead of me.

Just thought I'd enter a wrap-up in case anyone else is recording in this manner.

Long story short: everything works fine.

The answer to the immediate dilemma was/is: Apple doesn't allow adjustment of recording levels in Audacity when connecting a USB device such as my AudioHub 24/96 ADC. It's an Apple thing, not an Audacity thing.

The test SACD I initially used coincidentally had an extra-low db level, and I did apply post-record amplification, but it required no more than 5db. Subsequent recordings appear very close to "normal" and require little or no amplification. Maybe it's just a lucky catch that the low-gain switch on my input device creates a proper-level signal for recording. But regardless of inability to set precise recording levels, I should be set to make good recordings going forward. Everything sounds fine.

Thanks to everyone who responded.