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

Thursday, April 21, 2011

Testing Power Output from Old School Amps - Part 2 - Video Demo

I recently did a video review showing the details on how I measure output power on my old school amps. I've had a ton of questions with people wanting me to explain further the process. If you want to do this yourself, you'll most likely need to invest some money in the tools. At a minimum, you'll need the following:

  • 12v Automotive starter or Marine Deep Cycle battery or 12-14.4v Power Supply with enough output to handle your amp's load
  • True RMS Volt Meter
  • Oscilloscope (My Velleman HPS-50 has a built-in RMS Volt Meter)
  • Speakers or Resistors for "loading" the amp
Watch the video to see the components I use for my tests. 

Click the link if you prefer to see the video in HD (720 or 1080p):



Friday, April 1, 2011

More 90's Cheater Amps Coming Soon...

What's up old school fans? Sorry, it's been too long since my last post. I have acquired a few more "cheater" amps from the 90's I'll be testing soon. I've decided to stick with the "50 watt" (25x2) cheater amps as these are more affordable and easier to come by.

Here's a 1992'ish US-Amps US-50HCA, high-current, competition 25x2 amp:

US Amps US-50HCA - 1992 Model in 9.5/10 Condition

Another popular 25x2 cheater amp from the 90's was the HiFonics Ulysses. This mode is the Ulysses VIII, which has the Utilink connectors for speaker and power. Unfortunately, my amp was missing these connectors and since Zed stated these connectors are no longer made (the power connectors were specifically tooled for these amps and no longer manufactured). The speaker connectors are easier to come by. You can either spend $15-20US on eBay or search the Digi-Key catalog for a suitable replacement. I chose the latter.

Fully Polished 1996 HiFonics Ulysses VIII

More details on these cheater amps and maybe I'll be able to come across a few more to include in my shootout. I'm looking for 1) MTX 225HO 2) MTX MTA 225 (clone to the PPI Pro Mos 25) 3) Autotek 9050BTS and a few more I can't think of right now.

Here is the list of 90's cheater amps thus far for my shootout:

1) Rockford Fosgate Punch 45HD
2) Precision Power Pro Mos 25
3) Phoenix Gold MPS-2240
4) Orion 225HCCA (Gen2 and Gen3)
5) US Amps US-50HCA
6) HiFonics Ulysses VIII

So, how will I perform the shootout? Well, I'm thinking a true power output test using my dummy loads and oscilloscope as the first test. I plan to have the means of testing loads from 4ohms down to 1/2 ohm. Obviously, I'm not going to load amps, such as the Punch 45HD lower than 1ohm as it was not intended to handle extremely low impedance loads as some of the others were. Many people may argue the Punch 45HD should not even be considered as a cheater amp, but those people can do their own shootouts!

In addition to the power output tests, I'll also demo each amp powering one or more subwoofers. It will be interesting to see if the most powerful amp also controls the subwoofer(s) best. We'll find out soon enough...


Update: 6/27/11

Many of you have contacted me asking why am I taking so long to post the shootout between the cheater amps I have listed above. Honestly, I was hoping to get the HiFonics Ulysses VIII amps repaired as they were both dead. My repair tech said it would be about $100/ea to have them fixed and since I needed some other amps repaired, I decided to trade in the Ulysses amps. That said, I won't be getting them back, so I'll have to remove them from the test. I've seen a few Autotek 9050BTS's lately, so maybe I'll be able to pick up one of those for the shootout.

In addition, the Phoenix Gold MPS-2240 is experiencing the same issue as many 90's Phoenix Gold amps....leaky output capacitors. These capacitors will need to be swapped prior to any further testing with this amp. Too bad as it may be several months before I'm able to get around to having it repaired. 

Stay tuned for updates....