Analog to Digital (A/D) Converters

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TruBLUE

TruBLUE

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Recently I have been reading up on USB mics and one of the problems were that they had low quality A/D converters built into them.

So My question
1. At what point is a A/D converter considered HQ?
Are they 16, 24, or 32 bit?
Sample Rate 44.1KHz, 48KHz, 88.2KHZ, 96.6KHz, 128KHz?

2. At what point can't you hear the difference?
 
It's entirely possible to get 24bit 96kHz converters that suck.
A lot of the soundblaster stuff has the 24bit 96k logo on it, but it's completely unsuitable for audio recording.

Plenty of people record at 41/16, but there are others who swear by 24/96.
Personally I record at 24/48.


That's about as much as I can give you though.
Maybe some other users here can go into greater detail.
 
Its mostly you get what you pay for, a USB interface may serve you far better than a usb mic, trust me on this one :P and I record at 24/44.1 js
 
The sample rate and word length are completely independent of converter quality.

The main factors that influence quality in current A/D converters are the analog conditioning circuit that feeds the converter chip, the quality of the power supply and supply decoupling, and appropriate circuit board layout. These are all based on well established engineering principles.

The A/D chips used in the "best" converters seem to come from a handful of semiconductor manufacturers, and in commercial quantities cost in the order of $10 each or less. Those very same converter chips are used in "pro" equipment at all price points.

In my opinion, your sample rate should be chosen on the basis of the intended use for the audio eg 44.1kHz for CD, 48kHz for video.

Higher sample rates were once advocated in order to move harmful sampling and filtering artefacts (aliasing) out of the audio band. However, current A/D conversion uses a technique called oversampling which samples the audio at a frequency well above the audio band and then uses a so-called decimation filter to yield digital audio at the desired sample rate. (Oversampling occurs at the low mega-Herz range in an exact multiple of the required sample rate). The analog filter only needs only limit the input signal bandwidth to be below the oversampling frequency. That means that the analog filter can be very simple and operate at the range of a few hundred thousand Herz - well outside the nominal audio range of 20kHz, and well out of harms way.

Conventional wisdom recommends to track and process audio at 24 bits, and then export / dither to 16 bits as required.

My opinion is 44.1KHz is perfectly adequate for high quality audio.

Paul
 
When music is burned to a CD it is dropped to 16bit bit so does it really make a difference....Can you hear a difference when you record 24 bit
 
The rationale behind using 24 bit for tracking is probably twofold.

1 Dynamic range and noise floor. Tracking at 24 bits means you can track with peaks at say -12dB FS. This is safely away from digital clipping, but you still have heaps of dynamic range, and your capture is well above the noise floor.

2 Processing. A 24 bit audio sample has greater precision than 16 bit. In the DAW, that gets converted into a floating point format. Processing operations benefit (in theory) from having the greater precision at the outset (fewer rounding errors or something like that).

24 bit is actually the native resolution for a number of devices. Might as well use it and just downsample/dither when you export.

Paul
 
TruBLUE said:
When music is burned to a CD it is dropped to 16bit bit so does it really make a difference....Can you hear a difference when you record 24 bit
Click to expand...

Once it's on CD or a downloadable file the mix is fixed in place. When you record and mix and master you are doing all sorts of things to the signal that benefit from it being 24 bit. It's like taking photos that eventually end up the web. You don't take them at the final resolution and size, you take them at much higher resolution so you have more to work with when processing them for release.
 
TruBLUE said:
When music is burned to a CD it is dropped to 16bit bit so does it really make a difference....Can you hear a difference when you record 24 bit
Click to expand...

It's very hard to give a simple answer. "Only" 16 bits is still a big window for capturing most audio. We're talking maybe some extra noise way down in the mix, but maybe not.

Recording at 24 bits allows you to be more careless in level setting and still sound like a pro!
 
One more question lets say you have a mic capable of 16 bits and you set the DAW to record @ 32 bits how would that work out?
 
It's like watching an old black and white movie on a color TV. It's still going to be standard definition and black and white.
 
Steenamaroo said:
It's entirely possible to get 24bit 96kHz converters that suck.
A lot of the soundblaster stuff has the 24bit 96k logo on it, but it's completely unsuitable for audio recording.
Click to expand...

I doubt the AD is the quality bottleneck:
Sound Card Quality Report

The OP's USB mic has the preamp crammed in there too. It's probably a combination of a cheap mic and pre. The converter is the least of those concerns.
 
leddy said:
I doubt the AD is the quality bottleneck:
Sound Card Quality Report

The OP's USB mic has the preamp crammed in there too. It's probably a combination of a cheap mic and pre. The converter is the least of those concerns.
Click to expand...

I'm not saying anything's the bottleneck.
I'm just pointing out that numbers can be meaningless, or at least, not relevant.
 
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