Product Review

Bryston PowerPac 300 Monoblock Power Amplifier: A High Performance Upgrade for the Center Channel in that Big Receiver

April, 2004

John E. Johnson, Jr.


Click Photo Above to See a Larger Version


● Output: 300 Watts RMS into 8 Ohms,

    20 Hz - 20 kHz

● MFR: 1 Hz - 100 kHz

● THD: 0.007% 20 Hz - 20 kHz

● Noise: - 106 dB

● Input Impedance: 50 kOhms Unbalanced,

    20 kOhms Balanced

● Size: 4.5" Hx 8.4" W x 17" D

● Weight: 25 Pounds

● MSRP: $1,699 USA


Bryston, Ltd.


Many of us have nice receivers that, unfortunately, do not have enough power to drive the speakers to the kind of volume we like, particularly with action films.

A few months ago, I wrote a review of the AudioSource Amp 5.3 150 watt monoblock that is an ideal and inexpensive way to give yourself more power without purchasing a multi-channel outboard power amplifier for that $599 receiver. The reason that just adding one good power amplifier works so well, is that the center channel is where the biggest power demand is. Bass in DVD movie sound tracks may be re-directed to the subwoofer or main channels, but it is still important to have plenty of power in the center, because a combination of dialog and action can make voices sound mushy if there is insufficient power.

These days, you can spend $5,000 on a receiver. They are excellent quality, but still may have just a bit less power than we would really like to have. (Not all big receivers are lacking, but some of them are.)

The Bryston PowerPac 300 is an ideal solution for the high-end receivers. It delivers 300 watts RMS into 8 Ohms, and will easily drive 4 Ohm loads as well. Using this amp will deliver the quality of a high-end receiver amplifier, but also relieve the receiver from having to deliver so much power to all channels, using only one power supply.

The Design

The PowerPac 300 is one model in Bryston's PowerPac series, with the other models delivering 60 watts or 120 watts RMS into 8 Ohms. It replaces the PowerPac 250 in that series.

The model 300 weighs as much as most receivers, and a big percentage of what even the big receivers weigh. It's all in the power supply, which is quite large on the Bryston. So, for example, if you used seven of these with a 7.1 receiver, some of which boast 120 watts output per channel, the amplifier total weight would be 210 pounds!

Bryston builds amplifiers for the Pro market, and the heavy build quality necessary for that market rolls over into the consumer arena. If you look at the heat sinks on this unit in the photo, you can see that the area is about the same for an entire mass market receiver with seven channels. Heavy is good!

The power supply uses a 600 VA toroidal transformer and two 10,000 F capacitors with 95 Volts on them, for a total of 90 Joules of energy storage.

The 300 is long and thin, designed for placement on a shelf with other channels if you want to use more than one (it is obviously designed for multi-channel purposes, choosing two or three, or six, etc., I am just reviewing it in single channel use here.) It is also designed for mounting directly on the back of speakers.

All the controls and inputs are on one end of the chassis (photo shown below). The AC socket is grounded. The toggle on/off switch lets you choose between manual on/off or remote with 12 volt input to switch it. Both XLR balanced and RCA unbalanced input jacks are supplied. You choose which one you want with a small slider switch. You can use a 1/4" balanced phone plug in the middle of the XLR jack as well. This is part of the rollover from the Pro market, where phone plugs are commonly used.

The speaker binding posts are heavy duty.

The Sound

I have had this unit in my possession for some time now, and have used it in all sorts of situations, including the center channel from receivers, but also in a two-channel setting (the left channel in our CD player stereo setup, which includes a Classé CDP-10 CD player, BAT VK-5i preamplifier, and BAT VK-75SE power amplifier).

Regardless of the setup, the PowerPac 300 was exceptional in sound quality. I remember when the Bryston sound was equated with a hint of brightness. That is long gone now, as Bryston has revamped their designs. The sound was smooth, clean, and of course, powerful.

It had a bit more edge to it than the BAT VK-75SE, but all solid state amplifiers compare to a triode tube amp (the BAT) that way.

In the home theater setting, I used the 300 with a mass market receiver that was in the lab, but also with our Theta Casablanca SSP which has recently been upgraded from a II to a III (review coming soon). It worked beautifully with the 4 Ohm center channel configuration, and provided terrific clarity for dialog in movies. It delivered unending power for the sound effects that are in the center channel as well.

For example, in Star Wars: The Phantom Menace, the Pod Race has a race announcer who speaks while the crowd is roaring. If the center channel amp is not up to snuff, the announcer will be difficult to understand.

I never heard any evidence of clipping in the 300 regardless of where I was using it, and regardless of volume settings. An example is True Lies, the opening scenes where Harry blows up the castle and is being chased by the guards. It is very intense, and very demanding.

It never got hot to the touch, thanks to the huge heat sinks, but I would still suggest giving it plenty of ventilation if you plan to mount it in a cabinet.

On the Bench

All tests were conducted using the XLR balanced input.

At 1 kHz, the 300 is well within its spec of < 0.007% THD.

Using 5 kHz and 6 kHz input signals yielded very low IM distortion.

At 10 kHz, this was the only time we found THD to be higher than spec, but it is still very low.

Again, IMD is low using 10 kHz and 11 kHz input signals.

The measured frequency response was 1 dB 10 Hz to 96 kHz.


The Bryston PowerPac 300 monoblock power amplifier is a great product. It is a perfect center channel amplifier upgrade for that high-end receiver, but you might just find yourself getting more than one.


- John E. Johnson, Jr. -

Copyright 2004 Secrets of Home Theater & High Fidelity
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