Power Amplifiers

Primare A30.7 Seven-Channel Class D Power Amplifier

ARTICLE INDEX

Design and Setup

The Primare design philosophy is pure Swedish in that their primary aim is to provide high quality products that are easy for the end user to set up and use. Their surround processors, for example, don't contain a dizzying array of features with complicated settings and highly nested on-screen menus. You won't get every conceivable bell and whistle. Instead, Primare focuses on quality design, manufacturing and pure performance. I like that.

For better or worse, this philosophy carries over to the Primare A30.7 in a number of ways. I'll start with the "worse" part of that equation. The A30.7 doesn't have a front-panel standby button. There is a master power switch on the back panel. Also on the back panel are 12 volt trigger ins and outs. The obvious intent is for the installer to connect the Primare to your pre-pro's 12V trigger out and the unit's power on/off cycle would be controlled by your pre-pro. So this is an elegant solution for most installations. But as a reviewer, I like to mate products like this with all sorts of control amplifiers, some of which do not have triggers so that the absence of a front-panel power control is perplexing to me.

The other "worse" part is that the Primare A30.7 has three feet on the bottom of the unit. I thought this was a really great idea at first. You just need three feet to hold the unit in a stable position. The only problem was the single foot in the back of the unit caused it to teeter around quite a bit when I pulled the A30.7 out from the shelf to change out the cabling. This is also predominately a reviewer's quibble as most folks would set it up once and leave the unit installed for a long time. They wouldn't typically be changing out cables and interconnects the way a reviewer does.

Now on to the "better" part of this design equation. The Primare A30.7 has irrefutably excellent build quality. This baby is really put together. The cassis is heavy gauge alloy steel. The front panel logo is precision CNC milled. The audio connections are top quality gold-plated connectors; the unit is selectable unbalanced RCA or balanced XLR. The toggle selectors for the inputs are high grade. The A30.7 has heavy duty binding posts. And the unit shipped with a high quality power cord as well. All in all, the Primare A30.7 is a total class act, just like Primare's other products.

Let's cover the design features that Primare put in to play for the A30.7, their first Class D amplifier. This amplifier uses what Primare terms their Ultra Fast Power Device (UFPD) circuitry. This circuit utilizes proprietary chips that switch at 385 kHz. These may not be the fastest chips out there for Class D amplifiers, but they switch at more than 10x the highest "audible" frequency of 20 kHz and this would generally be considered an adequate switching frequency to cover the rated frequency band while minimizing the quantization error.

So the Primare A30.7 has some very fast switching output devices, but the real crux of the UFPD design lies in the implementation of an age-old design mechanism: global feedback. In the Primare UFPD design, there is a constant 26 db of global feedback. This would be difficult to achieve with conventional Class D amplifiers because of the dead times in the switching of the output transistors. Primare tackled this problem by designing the amplifier where the output stage and the low pass filter are not discrete. Instead, these two elements of the amp are integrated which makes the control of the feedback more immediate and precise. In this way Primare can provide more feedback across the audio band and the amp is more stable into real world speaker loads with their variable impedances throughout the audio band.

In Primare's own words, "This means that UFPD is able to drive any speaker, creating a vividly natural rhythmic sound while keeping power consumption at a fraction of that used by a traditional amplifier. With UFPD, Primare has inspired a new generation of smaller, more powerful hi-fidelity amplifiers, perfect for our environmentally conscious multi-channel age."

Primare also touts the A30.7's isolated PFC (Power Factor Control) power supply. The PFC power supply is said to match the phase of the A30.7 to the phase of your mains voltage so that the power draw of the amp has the least impact on your mains supply. The isolating stage of the converter works in a zero-voltage switching mode so as to reduce the electromagnetic interference in the circuit.

Looking under the hood of a Class D amplifier usually makes me giggle at least a little bit. It is just amazing that an amplifier capable of the type of power output (and, in the case of the Primare A30.7, the quality of sound) could be constructed from such a minimalist amount of parts. The most obvious thing missing from these amps is the huge, heavy and expensive transformer that is typical of conventional amplifiers. The Primare A30.7 did curiously include a forced-air cooling system. I didn't know it was there until I pulled the cover off the amp because it was so incredibly silent in its operation. And I wondered if it ever actually came on at all. The heat sinks were correspondingly small.