(Eric) wrote in message . com...
...i suppose the concept would be similar to any other amp, but I'd
really like to bench test my Soundstream Rubicon 1002 amplifier. At
least soundstream is a name brand rather then some other no name
brand, but they claim 200 watts x 2 into 4 ohms, and 500 into 2 ohm
stereo. Also, 400x1 into 8 ohm bridged and 1000 watts into 4 ohms
bridged. Hmm, I dunno but I'm a little bit leary here.. the numbers
dont seem to add up. Is there a way to verify that the amp is indeed
capable? I know a dummy load has to be put on it..

You will need a dummy load capable of dissipating all that power,an
Oscilloscope and function generator would be handy :-) a decent
DMM,you can get the RMS power from ohms law.
You will ofcourse also need a power supply :-)

I rewound an old microwave transformer.I cut the HV secondary off
completely,and rewound it with 2 pieces of 10 awg wire. about
10-15turns. each secondary went to it's own 25A bridge rectifier,and
the outputs were connected to .1F of filtering caps. (more would be
advisable,a couple Farads wouldn't hurt.)

a decent
DMM,you can get the RMS power from ohms law.
You will ofcourse also need a power supply :-)



Carefull with cheap DMMs when measuring RMS. They often have limited
bandwidth (mines 3dB down at 1kHz).

Gareth.

"Eric" wrote in message
om...
...i suppose the concept would be similar to any other amp, but I'd
really like to bench test my Soundstream Rubicon 1002 amplifier. At
least soundstream is a name brand rather then some other no name
brand, but they claim 200 watts x 2 into 4 ohms, and 500 into 2 ohm
stereo.

That suggests that the amp is optimized for 2 ohm operation, and actually
voltage-limited at higher impedances. I could see a savvy engineer designing
such a thing for mobile use.

Also, 400x1 into 8 ohm bridged and 1000 watts into 4 ohms
bridged.

That agrees with the unbridged numbers. I can't tell you that they are
telling the truth, but if they aren't telling the truth they are telling you
a plausible lie.

Hmm, I dunno but I'm a little bit leery here..

That comes with the territory - car sound. Ever hear of "Pyramid watts"?

;-)

the numbers don't seem to add up.

They paint a believable picture to me. But I can't tell you whether its
believable fact or believable fiction without some bench testing.

Is there a way to verify that the amp is indeed capable?

At these power levels that knowledge will cost you some bucks.

I know a dummy load has to be put on it..

Yes, and that means getting a number of precision resistors of considerable
size and cost. You can't cheap off here because the resistors not only need
to be able to dissipate lots of power, they need to dissipate lots of power
without changing their resistance. Last time I bought parts like these about
$250 went flying out the window.

Then there's the power supply. The power supply is mostly transformer and
capacitors, and the tip about rewinding a trashed microwave oven tranny is
interesting. The required filter caps could be "stiffening" caps. By now you
probably know what they cost. Unless you get some used at a desperate price,
at least another $100 just went out the window. You'll need a heavy bridge
rectifier - Radio Shack doesn't sell what you need!

Then there is some kind of device for monitoring clipping and distortion and
a good voltmeter. You can use your PC and some software for the former (if
your PC has a halfways decent sound card), but a good true RMS voltmeter
with adequate bandwidth is going to trash at least another C-note.

OK, so now you're out about $500 for parts and you're ready for some
interesting learning experiences!

;-)

Ironically, in the end you're going to judge this amp by how it works in
your car. My advice is to be sure to use lots of heavy copper wire to hook
it up because it looks like a piece that can draw and handle lots of amps.

BTW looking at their web site http://www.soundstream.com/features.html , it
appears that this (massive hype aside) possibly a really pretty good amp.
I'd give it a try in my car without the test bench histrionics ... ...if I
didn't already have the test bench!

;-)

"Arny Krueger" wrote in message
...
Then there's the power supply. The power supply is mostly transformer and
capacitors, and the tip about rewinding a trashed microwave oven tranny is
interesting. The required filter caps could be "stiffening" caps. By now
you
probably know what they cost. Unless you get some used at a desperate
price,
at least another $100 just went out the window. You'll need a heavy bridge
rectifier - Radio Shack doesn't sell what you need!

Everyone seems to use a difficult solution for power supply. I just use a
fully charged car battery. Sure you will get a little bit more voltage and
hence power when connected to a fast spinning alternator, but it's a fairly
realistic test compared to a bench supply. Calculate the difference if it
matters to you.

Trevor.

In article , "Trevor" wrote:

"Arny Krueger" wrote in message
...
Then there's the power supply. The power supply is mostly transformer and
capacitors, and the tip about rewinding a trashed microwave oven tranny is
interesting. The required filter caps could be "stiffening" caps. By now
you
probably know what they cost. Unless you get some used at a desperate
price,
at least another $100 just went out the window. You'll need a heavy bridge
rectifier - Radio Shack doesn't sell what you need!

Everyone seems to use a difficult solution for power supply. I just use a
fully charged car battery. Sure you will get a little bit more voltage and
hence power when connected to a fast spinning alternator, but it's a fairly
realistic test compared to a bench supply. Calculate the difference if it
matters to you.

An alternator needs to have the motor up maybe to at least 2500RPM or
more to get near full output. At idling its the battery 12volts the amp will
see and use anyway for high output from the amp.

greg

"gregs" wrote in message
...
In article , "Trevor"
wrote:
Everyone seems to use a difficult solution for power supply. I just use a
fully charged car battery. Sure you will get a little bit more voltage
and
hence power when connected to a fast spinning alternator, but it's a
fairly
realistic test compared to a bench supply. Calculate the difference if it
matters to you.

An alternator needs to have the motor up maybe to at least 2500RPM or
more to get near full output. At idling its the battery 12volts the amp
will
see and use anyway for high output from the amp.

That's my take, and why I specified "fast spinning alternator" above.

Trevor.

"Arny Krueger" wrote in message
...
Yes, and that means getting a number of precision resistors of
considerable
size and cost. You can't cheap off here because the resistors not only
need
to be able to dissipate lots of power, they need to dissipate lots of
power
without changing their resistance. Last time I bought parts like these
about
$250 went flying out the window.

Wind your own and measure the resistance while hot.
He's not after a certified standard after all.

Then there is some kind of device for monitoring clipping and distortion
and
a good voltmeter. You can use your PC and some software for the former (if
your PC has a halfways decent sound card), but a good true RMS voltmeter
with adequate bandwidth is going to trash at least another C-note.

Why does he need true RMS to measure sine waves?
A $20 multimeter will be adequate since he's probably not going to calibrate
it anyway.

Trevor.