Tuesday, April 26, 2011

Old School US Amps 50HCA vs. USA-50

I recently put a couple of US Amps amplifiers (1992'ish US-50HCA and 1999'ish USA-50) on the OldSchoolStereo.com test bench. The outcome was not quite what I expected. Both amplifiers are rated at 25 watts x 2 into 4ohms.

First up is the 1992'ish US-50HCA, which is finished in a beautiful blue color and is in AMAZING condition to be a nearly 20 year old amp. As with most of the late 80's and early 90's car amplifiers, the 50HCA has direct wiring, no terminal strips for the wiring connections. The 50HCA requires a 30A fuse and is stable to 1ohm mono or 0.5ohms stereo, according to the manual. Later models of this amp, known as the USA-50HC, require a 75A fuse, and are likely to be MUCH more underrated than this model. US Amps denoted their "competition" amps as either HCA,  HC or VLX series.

Proceed forward a few years to approximately 1999 and you could pick up a US Amps USA-50 in your choice of several colors. My sample is purple in color and has terminal strip connections for speakers and power. It also has a clear acrylic cover on the bottom of the amp to show off the "guts". The standard USA model amplifiers were rated for 1ohm stability in contrast to the HCA, HC or VLX series' 0.5ohm stability. The USA-50 requires a 25A fuse and also includes a 100Hz high pass or low pass crossover.

I was expecting the US-50HCA to be a beast, but not so much. Here are the results (RMS unless otherwise stated):

4ohms stereo - 33.4w/ch
2ohms stereo - 59.6w/ch
4ohms bridged - 126.3w
2ohms bridged - 198.2w
Max Output at 2ohms mono - 282.5w (hard clipping)

(The US-50HCA, like the Orion 225HCCA is rated to handle 1ohm mono and 0.5ohms stereo and I don't have the resistor bank loads to test these configurations yet.)

And the USA-50:

4ohms stereo - 38w/ch
2ohms stereo - 65w/ch
4ohms bridged - 133.7w
2ohms bridged - 167.6w
Max Output at 2ohms mono - 274.9w (hard clipping)

Surprised with the test results? I was. I guess the real test will be the 1 ohm mono test for the US-50HCA to see how much power it's really capable of. Now, let's see if I can sell a few amps to fund the needed resistors for the additional 800W 2ohm load.

Stay tuned, more coming soon...

See both amps pictured below; 50HCA in blue and USA-50 in purple...

US Amps US-50HCA on top and USA-50 on bottom

US Amps US-50HCA on top and USA-50 on bottom

US Amps US-50HCA Guts


eringrrlmblog said...

Their high current amps were 1/4 ohm stable, IIRC.

Unknown said...

I have a US Amps US-50HCA that I've had for many years and I ran it HARD for close to 10 years. Most of that time it was driving a pair of 12" 4ohm DVC subs wired in parallel for a 1 ohm load. I think it was officially rated at 380w @ 1ohm bridged and it would run a 1 ohm load all day long up to the point of being *cranked* with non-stop bass tunes. At that stage, you could pretty much cook with it, we used to buy a bag of ice to throw on the heat sink so we could drive around for a couple more hours. Ah, the good ole days!

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