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SounDigital SD300.2D Review (Car Amplifier)


Addicted to Fun and Learning
Aug 5, 2020
There MUST be someone in north America owning an Alpine PDX F6 to send it to Amir?! Let alone an Eton Core A2...
I have a v9 and f6 I offered to send in if a quick turn around time can be had. They are used in my truck currently which means I won't have any audio in it while they are out. I offered this in August and sent another message today to Amir.

I also offered a kicker key 180.4 and Sonic Electronix vad-m2 that I have on my shelf as extra things.


Feb 19, 2020
This is a review and detailed measurements of the SounDigital SD300.2D stereo car amplifier. It is on kind loan from a member. Apparently only 200 of these were built using GaN transistor technology. Not sure of the original cost ($1,300?).

From outside, the SD300 looks plain and and budget like:

View attachment 162952

This is no frills amplifier with large terminals for power, speakers and that is all she wrote. Did not get a manual so don't know what the power, X and triangle do. All web page references to it are gone.

SounDigital SD300.2D Measurements
I powered the unit using my Lithium custom power bank (rated for 100 amps continuous, 300 amps peak). Test voltage was nominally 13.4 volts and drop to 12.9 at peak power. Here is our dashboard:

View attachment 162953

Wow, this is stunningly good for a car amplifier. Actually, it would beat some 90% of the home amplifiers I have tested! Distortion is less than half of company spec.

Signal to noise ratio likewise, ranks up there especially in the good channel:
View attachment 162954

Frequency response shows that the amplifier filter does cause load dependency but it is at high enough frequency that should not be audible:

View attachment 162955

Crosstalk is good:
View attachment 162956

The amplifier took no time to reach stable operation:

View attachment 162957

Multitone test showed weakness at very low frequencies and high (latter being typical):

View attachment 162958

Fortunately the threshold of hearing is quite high in low frequencies so I don't expect an audible problem there.

Testing for power we get:

View attachment 162959

Allowing for more distortion and peak we get a bit more:

View attachment 162960

And 8 ohm:

View attachment 162961

So not a barn burner you would want to use for a sub and such.

I removed my AES filter and measured the full output spectrum:
View attachment 162963

Typical class D amplifier operates at around 300 kHz. Courtesy of GaN transistors, this has been upped substantially to 800 kHz. This is why the filter ringing was pushed up correspondingly in frequency response test. Very nice.

Edit: forgot to post the stepped frequency test:

View attachment 163140

When I test car audio gear, I automatically lower my expectations. Imagine my surprise when I saw the dashboard and how the SD300.2D outperforms majority of home amplifiers let alone car audio. Some smart designer in Brazil really took advantage of GaN technology to produce very low distortion and high performance amplifier. Alas, if it cost $1,300 for so "little" power, I can see how it would not sell as a mainstream product. Hope we see some variation of this come back to market and at higher power levels.

Oh, I forgot to note that the amplifier just got a bit warm during testing. So it is very efficient to boot.

It is my pleasure to recommend the SounDigital SD300.2D. A feather in the cap of our Brazilian members and visitors! :)

As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
This performance would be considerably more impressive if it didn’t come at such a high price. This is roughly 10 times the price of a typical 2 channel car amp. Grab one of those for testing. That would be a more useful comparison. Sorry I don’t have any to send but somebody must have a Kicker 43DXA125.2 or similar.



Master Contributor
Forum Donor
Dec 9, 2019
Thank you for the reply. I specialized in car audio in-warranty service for Coustic, Soundstream, Sony, Pioneer and Clarion and serviced most everything that was out of warranty too. I acted as the Canada warranty service depot for Coustic and Soundstream, had all the parts in stock for service and my workbench was tooled up specially for car audio. So the big ~3 foot long high power class A/AB car amps where sent from across Canada to me for service. The difference in size, power consumption and heat generated compared to then and now is incredible. I'm used to seeing big numbers for the amps current draw and to see that the current draw for your Soundigital car amp is 32A is pretty cool. For comparison purposes I provide pics of the old inefficient car amps so peeps can see what a old veryyy hot running class AB Coustic and Soundstream car amp looks like inside.


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