Friday, November 02, 2007

iTrax Almost Ready

In a previous blog post, What is HD Audio?, I mentioned that AIX Records was going to launch a new website where you could purchase and download 24bit/96KHz high resolution audio tracks and albums. It looks like they are almost ready to go.

For those of you who have never heard a HD audio track, here's your chance. They let you download a sample track after you register on their website. Their HD audio was actually recorded using HD recording equipment. This isn't previously mastered stuff resampled into HD, like a lot of music currently on SACD or DVD-Audio. It was recorded, processed and mastered in high resolution.

To check this out, go to their website at

When you register, they will reward you with a sample track that you can download. If you pick 'Login' at the bottom of the webpage, it will take you to another page that will let you register. I think the website is still in beta, so some things may not be working. Unfortunately, they don't let you download both a 16bit/44.1KHz version and a 24bit/96KHz version for comparison purposes, but at least you can try out the 24bit/96KHz track.

BTW, it sounds really good on our demo system. I'm looking forward to purchasing more of their music. I'm not familiar with most of their artists, so I'm open to any recommendations.

Thursday, November 01, 2007

Go Green with Class D Amps

Here's an article from Electronic Design that talks about the advantages of running a Class D amp when compared to other amplifier designs with regard to power efficiency.

They explain that an amplifier works by applying a voltage of alternating polarity to a loudspeaker, driving it back and forth to move the air that produces the sound. The amp basically has 2 power rails for the + and - polarity voltages.

With a Class A amp, both switches are on simultaneously to create the required voltage, so they're only about 15% efficient. This means that only 15% of the power is used to drive the speakers. The other 85% is lost as heat. That's why the higher power (over 100W) Class A amps are usually pretty large and include massive heat sinks. With Class B amps, only one switch is on at a time, resulting in efficiencies of around 75%. Unfortunately the trade off is poorer sound quality. Class AB is a combination or compromise between A and B with both switches on simultaneously, but the non-load carrying rail was only minimally on. This improved the sound, but only resulted in efficiencies of about 30% due to switching losses. The Class D amp does this by switching these voltages on and off. With the Class D amps, the switching losses are very low resulting in an overall efficiency of more than 90% with very good sound quality.

Read the article if you are interested in more of the details.