I have written more than 400 articles about audio and video products over the years. I have learned a lot about what makes a product great, i.e., World Class. So, I am preparing this article to discuss some of those products that I have reviewed, but also, some that I didn’t get around to reviewing, but know that they are really terrific. They will be covered in this article, as I get around to writing about them. So, let’s get started.

OPPO UDP-205 4K Blu-ray Player

The OPPO UDP-205 4K Blu-ray player followed on the OPPO BDP-105 Blu-ray player. The 105 was a masterpiece of engineering, and was considered to be the best HD (1080p) player in the world. When 4K came along, the UDP-205 replaced it. The problem was that 4K was so new, very few of the 205 players were sold. This caused a cash flow problem at OPPO, and the company had to cease doing business. Also, the 205 was priced at $1,295, which was too expensive for the mass market, but not at a level that the market would consider it high-end. It was tragic not only for OPPO, but for consumers

You can change your mind now and get one on Amazon, sold by people who bought them and now are selling them at a premium  – about $3,500. This is what the UDP-205 is actually worth. It is a superb player. I have two of them and will never let them go. I believe that if OPPO had priced them at $3,500, more of them would have been sold, but that is just my opinion.

It is superbly constructed with myriad inputs and outputs, including analog and digital.

Using one of the USB 3.0 jacks, you can connect a hard drive on which you have copied music files. Then, you download an app onto your cell phone or pad, and you can connect with the UDP-205 through your home network and simply touch the music file of your choice on your phone or pad. The UDP-205 will play the file.

Distortion is very low, as shown below.

The OPPO UDP-205 is the heart of my A/V system. It handles 4K Blu-ray movie discs with aplomb. I only wish it were still available so I could purchase another one.

Pass Labs Xs 300 Monoblock Power Amplifiers

There are 36 pairs of transistors in the output stage (36 devices for each of the two push-pull phases), and 40 devices in the current sources (located in the bottom chassis). So, that is 112 transistors for a 300 watt amplifier. The current sources in the output stage are constant current sources, used solely to bias up the output stage with a single-ended character. The amplifier itself is a voltage source design.

The large number of output devices results in very low noise, but also, an excellent transient dynamic capability. This, plus configuring the amplifier for 240 volt AC use, produces amazing dynamics overall.

An Xs 300 consists of two chassis, as shown below. The power supply is in the lower chassis, and the control circuits are in the upper chassis.

A pair of these amplifiers weigh more than a quarter ton.

The design is quite different than most power amplifiers. It was not designed for the lowest distortion. It was designed for the best sound, which includes some harmonics.

Shown below is the Xs 300 with a 5 volt output into 8 ohms. The second-order harmonic is dominant.

Now, look at the output at 40 volts. There are many harmonics, but the total is less than 0.5% THD+N.

This is very different from the way that most amplifiers perform. The distortion is part of the desired sound. It is not a reflection of an amplifier being stressed. The amplifier is coasting along, but producing a desired amount of harmonic distortion. However, it was not designed to have a specific set of distortion peaks. The circuit was designed by listening to the amplifier with different arrangements of the amplifier parts, and when the best sound was heard – as determined by a group of the engineers and other people listening to the amplifier – that was the circuit that was finalized. The distortion peaks ended up wherever they were.

The Xs 300 operates in Pure Class A throughout the 300 watt specification. That is one reason the amplifier is so large. It takes a huge power supply to deliver that kind of power. There are 112 output transistors and 400,000 µF of power supply capacitance.

The results are spectacular!