‘Freeing the watts’: PA 16 in bridged mode

July 01 2022

StormAudio is all about flexibility and ease of use. This is also true for our amplifiers.

The PA 8 Ultra is a perfect example, with the option of adding any combination of single-ended and bridge-tied load channels, scaling the unit from 4 to 8 channels and ranging from 200W to 800W with 8 ohms load. The PA 8 Ultra is not only versatile but also without compromise: you can simultaneously drive all channels—whether in single-ended or bridge-tied load mode—to the maximum output capability without limitation in current.

For our other amplifier offering, the PA 16, we regularly get feedback that it is the best in terms of cost vs power vs number of channels offered on the market. However, what it lacked is the flexibility to be bridgeable. This, however, is not entirely true.

The design of the PA 16 shares the same principle as the PA 8 Ultra, meaning that it can also offer the maximum power capability to all 16ch driven simultaneously. We defend this philosophy at StormAudio, but often it is too stringent when considering the reality of most systems and signals that are played. Indeed, in home cinema, most of the time you will find speakers that are limited in bandwidth (usually above 80 Hz) and some dedicated low-frequency channels (<80 Hz). Also, in real life, signals (apart from the LFE and the bass-managed, low-frequency signals) are rarely correlated, thus it is rare to see all channels needing full power at the exact same time and same frequency.

With this in mind, we have decided to “free our watts” by opening up how you can use the PA 16 in bridge-tied load mode.

Both PA 8 Ultra and PA 16 share the same circuit topology, with a total of four power supplies. In the case of the PA8 Ultra, each power supply drives two channels, while it drives four channels in the PA 16. While you could create up to 8ch in bridge-tied load mode with a PA 16, we recommend not to do more than 4ch bridged total per unit to avoid meeting the current limitations that can lead to some sound cut.

When bridging channels, you can still use the remaining outputs to drive additional speakers in single-ended mode. Keep in mind that you need to consider balancing the amount of power available per group of 4ch: 1-4, 5-8, 9-12, 13-16 due to our power-supply structure.

This translates into the following recommendations:

You can bridge ch1-2, ch5-6, ch9-10 and ch13-14,
You can use other channels: 3, 4, 7, 8, 11, 12, 15 and 16 for other speakers.

The unit is stable with low impedance, including when used in bridged mode. But it is important to balance the power needs in terms of channel distribution to avoid current limitation. It is important to point out that when in bridged mode the capability rises up to 800W: your speakers or subwoofers must be really demanding for the power supply to kneel down.

In order to use the PA 16 in bridged mode, you simply need to use a “Y” type XLR cable, driving the two channels with the same signal and then connect between the positive of ch1 and negative of ch2 (you can refer to PA8U wiring for reference).

A technical bulletin will be made available soon in our Client Portal.