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Discussion Starter #1
Got some things in today. The 9886 is for my friend. The zapco is for myself.

9886:
No headunit preout clipping even at full volume on a 0dB, 1000hz tone.
Preout voltage = 4.27v.








Zapco 1000.4 clipping:
This is something I wanted to see for myself; testing voltage out without a load and with a load.

The load used was measured at 3.5ohms. This dummy load came from parts express.

Used the alpine headunit, same test tone at full volume. controlled attenuation from the zapco software to control clipping points.
The power supply presents a steady 13.8v output to the amp.

Alright, so here we go...

No load presented. Just took measurements of the bare wires coming out of the amp:
As you can see in the picture below, the maximum non-clipped voltage is about 22.75vac. That equates to 144w rms.



Now with the dummy load put in, and (approximately) the same voltage reading, you can see how severely clipping the signal is:



Now, with the dummy load, I backed the output of the amp down to the highest non-clipped point. That gives me 17.56vac. This = 89w rms.




So, there you have it. :)
 

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That's pretty impressive, the HU I mean. I have always just assumed, as it always has been said in the past, that HUs clipped at ~90%. Maybe I will scope mine tomorrow...
 

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Got some things in today. The 9886 is for my friend. The zapco is for myself.

9886:
No headunit preout clipping even at full volume on a 0dB, 1000hz tone.
Preout voltage = 4.27v.

I just looked at the manual, Alpine calls out 4v into a 10k ohm load.

Plus not all DVMs are created equal when reading a RMS value of like said 1khz. There maybe be some error in measured value.

:rockon:
 

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Having a scope in your basement makes it official - you've gone to a place from which you can never return. Actually, just deciding you needed one put you there. Is putting the terminals on your tongue and tasting the clipping too good for you all of a sudden? :D
 

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Hasn't been scoped, but my 9886 is clean to max volume.
 

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Discussion Starter #10
Could be the test setup. Could be how Zapco does their setups. Too many variables.

For simplicity I set everything to 0dB (on the rca/symbilink converter). I still wonder if the software’s ‘headroom’ feature has anything to do with this.

I also wonder how kicking up the gain stage at the converter to +6 or +12 (highest) dB would change things.

No idea. I just set the test up how you see it; nothing fancy. A dummy load, an oscope, a DMM (that isn’t too great, but works within reason), and a test tone. Turned volume up on headunit to max undistorted output and then started toying with the gain stage of the amplifier until it hit clipping.

For myself, this is how I will always test. I only really do this stuff for my own curiosity and post here just for those who might give a flying fart, though I’ve started leaning towards not sharing at all due to the hassle of taking pictures and making sure everything can be seen to prove the test setup. If someone has input on why the results I obtained are different than the published specs, I’d be interested in hearing. Maybe I need to tailor my setup to get the ‘correct’ results. Regardless, I really don’t know how much more simpler I could have made my test. :)
 

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Could be the test setup. Could be how Zapco does their setups. Too many variables.

For simplicity I set everything to 0dB (on the rca/symbilink converter). I still wonder if the software’s ‘headroom’ feature has anything to do with this.

I also wonder how kicking up the gain stage at the converter to +6 or +12 (highest) dB would change things.

No idea. I just set the test up how you see it; nothing fancy. A dummy load, an oscope, a DMM (that isn’t too great, but works within reason), and a test tone. Turned volume up on headunit to max undistorted output and then started toying with the gain stage of the amplifier until it hit clipping.

For myself, this is how I will always test. I only really do this stuff for my own curiosity and post here just for those who might give a flying fart, though I’ve started leaning towards not sharing at all due to the hassle of taking pictures and making sure everything can be seen to prove the test setup. If someone has input on why the results I obtained are different than the published specs, I’d be interested in hearing. Maybe I need to tailor my setup to get the ‘correct’ results. Regardless, I really don’t know how much more simpler I could have made my test. :)
How big of a power supply are you using? That is probably why the power output isnt right
 

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Erin,

Did you monitor the PS voltage during the test? If so, did it drop under 13.8V? What size/capacity was the PS? Finally, was it an intelligent powersupply that limits current to maintain voltage? Otherwise your results should be spot on.

I got the HD600/4 and I am about to do some testing myself. The first test will be 1khz driving a single channel with a dummy load (should be directly comparable to your test). The second will be the same as the first but using broadband noise as the signal. The third should be the same conditions as two but using a sub as the load. The fourth and final test would be all four channels driven with noise into four coils on subs.

I'll post for comparison.

BTW - the PS will be two optima blues being fed by a 100 amp charger.

Should be big fun and YES, I am a gEEk.
 

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Discussion Starter #17
I didn't keep the DMM leads on the power supply the whole time, unfortunately. However, when I had this PS hooked up to my car a few weeks ago, it kept a solid 13.8v to my entire system. I would expect it to the same with only one amp. But, again, I can't say 100%.


The PS's amperage is rated for 55amps; fuse rating totals 60amp. Should be adequate for this testing I would expect. But, that's a good point.


The power supply is essentially a cascade power supply. As I understand it, it's from the mfg of the cascade supplies; just not labeled 'cascade'.
Here's a spec sheet:
http://www.cascadeaudio.com/power_converters/pdf/aps_faq.pdf
 

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I would be interested in seeing a line diagram of your test setup and what your settings on the o-scope were...

E~
 

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Discussion Starter #19
I would be interested in seeing a line diagram of your test setup and what your settings on the o-scope were...

E~
Line diagram?

headunit -> amp -> dummy load

:confused:
;)

You should be able to make the settings of the oscope out from the pictures if you click on them and enlarge them.
 
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