This article is about two new power amplifiers from JBL Synthesis: the SMA8300 and SMA4750. JBL Synthesis produces a range of high-performance home theater products, including speakers, surround sound processors, and power amplifiers. They are by far one of our favorite home theater brands at Audio Advice, as an all JBL Synthesis home theater is considered by many to be as good as it gets.

These two new power amps are so flexible that they actually replace 5 models from their previous lineup. Now, we have to say upfront that these amplifiers are not for everyone. They are designed to work best with JBL speakers and subwoofers. While these are not exactly inexpensive, they are extremely powerful with some very unique tuning and installation features. We do see them as perfect matches for many JBL Synthesis home theaters and media rooms. Plus, they will team up well for people looking for a high-performance multi-room audio system using JBL architectural speakers. Finally, the SMA4750, while a perfect match for JBL subwoofers and some of their upper-end speakers could also be used for anyone looking for extreme power with some very unique fine-tuning capabilities you do not normally find in a power amplifier.

JBL has a long history in the music industry, from being the speakers behind the Grateful Dead’s famous wall of sound, to studio and commercial theater use around the world, to world-class music halls like the Ryman Auditorium in Nashville.

Way back in 1983, when home theater was just in its infancy, Lucasfilm chose JBL to develop the first commercial THX®-licensed cinema speaker system. After designing these systems for commercial theaters in 1992, JBL Synthesis released the first home theater system using the same technology, and the rest is history.

One big distinction JBL had with their early Synthesis systems compared to the competition back then was the ability to fine-tune the system to the listening space. This was long before things like Dirac, Audessy, and others came on the scene. JBL pulled technology from their Pro Sound division, where tuning a concert space is critical to a good experience. In those early days, it took a JBL technician traveling to your home and spending the day calibrating your theater using the variety of tools from JBL Pro software, as there was no way for an individual to do this on their own.

As technology moved forward, room correction became easier for the average DIY person with software like Dirac and others. But you can make things even better if you can find the problems in your room and correct them ahead of the room correction software. This is called Pre Equalization or PEQ. If you do this, when you run the test tones, the software is reading a signal that is much closer to ideal, so it doesn’t have to work as hard to fix it. The catch is, you will only find PEQ on ultra high-end surround sound processors, or have to go a somewhat clunky route and use an external equalizer and its software.

Amplifier power is another area that has been evolving over the years. Soundtracks in today’s action movies can be extremely demanding. Sometimes, you'll have several seconds of thundering bass coupled with explosive special effects. This type of demand can really tax a system, and is why having lots of reserve power is very important. Without enough power, you may encounter clipping or distortion, which will ruin your listening experience.

And this is just where these new amps come in. These two new amplifiers from JBL Synthesis give you both huge amounts of reserve power with easy-to-use PEQ and more. Let’s take a look at the details.

The SMA8300 and SMA4750 are a complete redo of their SDA 8300 and SDA 4600 power amplifiers. These had been the go-to amps for JBL Synthesis systems, but their engineers knew they could be improved on.

JBL is part of the Harman Group, which is owned by Samsung. Crown Audio is also part of the Harman Group and has been making professional amplifiers since 1947. JBL leveraged this partnership for some of their amplifiers, like the ones these new models replace. The catch was that these amps used different types of connectors you don't see in home theater gear and required the use of JBL’s Audio Architect software to configure them, which had a pretty steep learning curve. They were also designed to sit in large racks at concert venues where fan noise is not really an issue.

In a brilliant move, JBL tasked one of their engineers, who had a long background in residential home theater, to take these to an entirely different level. Everything about these amps has been improved to give better sound, more power, home theater-friendly connections, and best of all, a new software interface anyone somewhat technical can easily use.

Features Shared By Both Models

Improved Connections

The amplifiers they replaced used what is called a Phoenix type connector for the incoming audio signal. This connector uses bare wire with a screw down terminal which is obviously not used in the home audio world. JBL Synthesis replaced all of these with solid XLR Balanced input connections.

The speaker terminals on the older ones also used a barrier strip speaker connector, which, again, is not commonly used in home theater. These were switched out to heavy-duty binding posts that accept up to 10-gauge bare wire, a spade lug, or a banana plug.

Audiophile Level Digital

Any amplifier like this needs to convert the incoming analog audio signal into digital for all of its built-in processing. Then, the signal is converted back into analog for the amplifier stage. The parts used for these two conversion processes can have a pretty big impact on the ultimate musicality of the power amplifier. While we could not get the exact part number of the A to D or D to A converters, we do know they went with audiophile-grade AKM parts. AKM DACs are well respected in the high-performance audio community.

More and Better Power

The power output increased on both models, but more importantly, the power supplies were improved to give more reserve for those dynamic musical peaks. The engineers evaluated everything about the signal path, and the end result is an amplifier with a sound that can compete against some of the best home theater power amplifiers.

Far Less Noise

In the commercial world, the original JBL Synthesis amps were derived from, fan noise is never a problem. But of course, in a residential space, it is a big deal. Audio Advice usually installed the older amps in a separate room to keep the fan noise from being an issue. The entire topology of the SMA8300 and SMA4750 was redone to reduce fan noise. They went from being quite loud to almost silent at normal levels and only 50 dB at continuous full power which is an incredible improvement!

Improved Power On/Off Control

The older models used contact closures to automatically power the amps on and off. This is very common in the commercial space, but does require a controller of some sort to provide the contact closure. JBL switched this out to the standard 12-volt trigger we see on all home audio components for power control. Plus, you also get wake on LAN and signal sensing power on/off should you wish to go that route.

Web-Based Set Up Interface

As we said earlier, the previous models needed Harman’s Audio Architect software to configure them. While this is a really feature-rich program that will do just about anything, it has a steep learning curve and is designed more for an engineer managing racks and racks of power amps.

For these new models, the JBL team took all of the great features of Audio Architect and created a web interface that is simple to use for someone with basic DIY skills.

Describing everything it can do would be far too much to go over, so we will just cover the high points.

From a channel management standpoint, you can make any channel a single channel or you can configure two channels to be bridged for more power. You can also route any of the audio inputs to any channel should you wish, but better yet, you can route one input to more than one channel. This comes in handy for at least four applications we can think of.

The first is for biamping, triamping, or quad amping speakers where you have separate channels of power for different sections of a speaker. Each channel then gives you individual control over low and high pass filters, the slope and type of filter used. So if you have speakers that require biamping or more, these amps are a dream for ease of set up.

Or if you want to passively biamp where the crossovers are still inside your speakers, but you have separate connections on the speaker for high and low, you can send one incoming signal to two channels without the need for any external splitters.

The other use for this would be multiroom audio where you might have 4 or more speakers in a room and you just have a stereo feed.

Another great use we see a lot is where the theater space has more than one pair of surround speakers, to cover multiple rows of seating. You could easily set this up within the amp to take the pair of surround channels coming in and route it to two pair of speakers rather than doing some kind of external splitter cable.

Inside this part of the config you can have the amp play pink noise on a channel to confirm you have connected everything properly.

Another big one is the PEQ section for each channel. You will find a nice graphical interface with an 8 band full parametric equalizer. If you have a way to measure the response of your speakers, this will let you knock down some of the peaks in front of the room correction in your AV processor, which is always a plus.

JBL has also measured how their speakers perform in average rooms and has loaded PEQ curves for just about every speaker they make. These are easily loaded in with the graphical interface.

Those are the high points, but there are many more features built in that make it easy to set these up, especially if you have more than one in a system.

Now we will look at each of these two models to help you understand where they might fit into your system.

Conclusion

These are incredible new amps, but we do wish they would come out with a lower power version at a reduced cost to open up all the built in tuning to more people for both home theater and multi room audio. Something like the 8300 with 100 watts per channel would be really cool to see.

But nonetheless, the SMA8300 and SMA4750 from JBL Synthesis will open up JBL sound and tuning to a whole new market of people. You no longer need custom software to configure these and you can use standard audio connections. The power of the SMA8300 will be plenty for almost all home theaters and if you need more, there is the SMA4750. If you are considering a JBL Synthesis theater, these should be your first choice for power.

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