Soundstream Class A 50 II Oldschool Car Amplifier Review

We are, who grow up in 90's probably know that the car audio at that time is full of great stuff. One of the most admirable car audio amplifier, at least for myself, is comes from Soundstream. The Soundstream Class A series built in very early 1991 and it is the high end car amplifier you can buy and put inside you car stereo system. I can tell you that this still the great sounding car amplifier until now.  Then why it is still great? Because it runs in Class A bias to achieve the best sounding amplifier. In audio world, the class A bias is well known as the highest rank in sound quality. The design that makes it great and the careful components chosen is what makes it run stable. I used to installed and playing this amplifier on my car ten years ago, but not this unit, it is a different type. At that time is the Soundstream Class A 100 II, dual channel 50 watt x 2 pure class A amplifier. This one in this review is the smaller version, the Soundstream Class A 50 II that only run 25 watt pure class A. When the first release, the price of this amplifier is US$400.

This Soundstream Class A 50 II size is very compact. It is slightly bigger than 1 DIN head unit. The bigger version is the A 100 II I had long time ago is exactly twice bigger than this. I think they are both sound great and the only difference is the power output.

As I said earlier the Class A amplifier required high quality material in the heat-sink. It should dissipate heat quickly because the power transistor are always get the full bias, means it run at 100% even in no input signal present. Look at this Soundstream heat-sink. I never had any high quality aluminium material like this on other amplifier. Soundstream only using this fine material in this series and sadly after that, no more high quality heat-sink same like this anymore. This is the product that appreciated until now.

The input panel of this Soundstream is located in one side only. That means the installation will be more tidy because all cables goes to one direction of the amplifier.

The RCA input signal is gold plated high quality RCA plugs. In the middle of it has small red color LED light to tell this amplifier is in operate condition when lit.

The cables terminal is standard bare cable holder with screw on the top to secure all the cables in it.

This is the opposite side of the amplifier. It is pretty clean.

The only adjustment on this amplifier is located on the bottom of the chassis. They are securely covered by plastic cap.

The setup is for using this amplifier in stereo or bridge mono.

Also the replacement fuse for each channel of the speakers output.

And the output impedance setup to match with the speakers that are using with this amplifier.

And here is the internal components. On the left side is the amplifier circuit and the right side is the power supply circuit. It is so simple and not so much components on it.

The amplifier circuit is only using 3 small bipolar transistor and 2 final transistor for each channel. You can not see the final transistor because it is placed underneath the PCB directly attach to the heat-sink.

This simple design is remind me to the great audio amplifier designer and guru, Mr. Nelson Pass. You also probably know that this amplifier is also his design as well.

The power supply section on this A 50 II has the same transformer size compare to the A 100 II. I wondering this A 50 II should has bigger headroom for that.

There is two capacitor for the amplifier section, each rated 2200uF. It is quite small in my opinion for Class A amplifier.

I made several connector to connect this car amplifier to be working at my home audio system. I am not yet make any audio upgrade to my car yet and the only possible to review the sound quality from this amplifier is by testing in my home audio system. This amplifier will connect to my existing speakers, with audio signal input from my Chord Mojo and this amplifier powered by 40 Ah car battery.

At the first time the music played, it is really shows what Class A amplifier makes a difference with others. The three dimensional vocal voices from the music is really a breath-taking experience. It is the soul of the singer and the weight of it deliver really well with this amplifier. Listening to it just like hearing many layer in mid-range sound, makes the singer virtually presence. The mid-bass also great in this amplifier. I could hear the beat with great amount of loudness clearly. On top of that, they still have good music separation.

The high frequency sound from this amplifier is not over blowing. Unlike the First Watt F5 amplifier that has very extended high frequency, this Soundstream Class A 50 II treble not very extended but it is just right. This may have some draw backs in the lack of wider sound-stages and highs detail. But that still count okay, thus more focus and bodied sound in the center of listening position. This sound signature is really remind me of the sound from the Elektor Mini Crescendo Amplifier that also very popular among DIY audio builder on the same years.

I playing some music for about an hour and more until I saw some drop amount of voltage from the car battery. It is now bellow 12 volt and I think I should end this listening session soon. When I touch the heat-sink, it is not crazy hot. Unlike F5 amplifier or it's brother, the A 100 II which with this quite long amplifier operation condition, you barely cannot touch the heat-sink.

This Soundstream Class A50 II is still the great amplifier even by today standard for sure. I will put this amplifier on my car as a simple 2 channel car audio setup soon.

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