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Ampeg SVT-7 Pro TEST
- Thread starter f.c.geil
- Start date
- Jun 29, 2006
- 5,148
- 3,217
- Disclosures
- President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
The specifications given in the manual by Ampeg are 600 watts rms @ 8 ohms at 5% THD and 1000 watts rms @ 4 ohms at 5% THD which is the THD that was correctly used by Bass Gear Magazine for their measurements.
What numbers would you have gotten at 5% THD?
IIRC, somewhere in the neighborhood of 590 watts @ 8 ohms, and 940 @ 4 ohms. I didn't keep record of intermediate steps, though, I just wanted to see what it takes to get Ampeg's output. Even so, 98% and 94%, respectively, of rated power seems to be well within tolerances, and far less variance than anyone can hear.
Starting with a slightly low line, and doing NO correction, yo come up with 40 W shy of claimed DEFINITELY suggests the amp will in fact do what it is claimed to do when tested at a stable 120V.
To those who would say "nobody has a regulated line", the vast majority of OTHER amps are tested in the exact same manner, with 120V maintained, and will suffer more-or-less the exact same reduction in power with mains voltage.
So the argumant of "I don't have 120V" must be applied to EVERY amplifier power spec. Not just one brand.
And the 8PRO has an unfair advantage..... because it has a "PFC" front end on the power supply, it will produce the exact same performance within close limits, using mains voltages anywhere from about 95VAC to 250VAC.
So low mains voltage will have no effect on it so long as the voltage is not entirely stupid....
Most units do not have that feature, and there is no particular reason for them to add it at the present time.
What were your gain and volume settings? Did you measure distortion out of the preamp as well as the power amp? Not sure if any of this matters, just curious.
The difference in output voltage between 763W/4 and 961W/4 is about 55V vs 62V. About a 12% difference, which is quite a bit. The difference in voltage between 961W/4 and 1000W/4 is about 1V.... or roughly 2%, no doubt easily within the margin of error.
As for instrumentation, there is some difference in the way a true RMS voltmeter reads, and the way a "corrected averaging" voltmeter reads...Don't know which was used in this latest test.
But 6% THD is probably not too far into the range where the difference is a big factor. The difference is only about 10% at worst case comparing a full square wave to a sine, but clearly 6% THD is not a square wave.
If this test is valid, it has reproduced one important part of the BGM test.... the "no adjustment, just plug it in and test power" methodology.
Certainly interesting, and (again if valid), throws another data point into the mix, one tending to support the manufacturer claims.
As for instrumentation, there is some difference in the way a true RMS voltmeter reads, and the way a "corrected averaging" voltmeter reads...Don't know which was used in this latest test.
But 6% THD is probably not too far into the range where the difference is a big factor. The difference is only about 10% at worst case comparing a full square wave to a sine, but clearly 6% THD is not a square wave.
If this test is valid, it has reproduced one important part of the BGM test.... the "no adjustment, just plug it in and test power" methodology.
Certainly interesting, and (again if valid), throws another data point into the mix, one tending to support the manufacturer claims.
Which is interesting. Does this mean Ampeg has a quality control issue?
If they can't send a properly functional amp to a test.
Was the voltage measurement with a "true RMS" meter or from scope pattern? If a meter do you know the error rate at 1 KHz?
Not looking for fights here people, just trying to get more info on the variables of the test
. You really should have adhered to the 5% THD or at least made good notes at that point 
6% THD power output level while acceptable was not in question. Just notes for next time
Thank you for doing this and thank your friend for allowing it to be done with his amp! A good layman's result, controls and checks that BGM used maybe missing. But that is neither her or there.
Perhaps BGM will offer to fly tekdiver500ft and his friend, along with their amp, down to the BGM test lab. Then, they could compare this amp to the original test amp, using both test methods. Perhaps this would shed some light on the issue.
Perhaps BGM will offer to fly tekdiver500ft and his friend, along with their amp, down to the BGM test lab. Then, they could compare this amp to the original test amp, using both test methods. Perhaps this would shed some light on the issue.
Yeah, well the two results are very different.
Settle down folks we have a new set of data, yes. So now we have manufacturers tested claims, BGM's professionally preformed data, and a layman's test results with unknowns in the test preformed.
A TEST is not a TEST. Only valid when checks and controls are present and repeatable. And we still are unclear as to what "standard" test method was used for the original test data to know if it is repeatable.
A TEST is not a TEST. Only valid when checks and controls are present and repeatable. And we still are unclear as to what "standard" test method was used for the original test data to know if it is repeatable.
Settle down folks we have a new set of data, yes. So now we have manufacturers tested claims, BGM's professionally preformed data, and a layman's test results with unknowns in the test preformed.
A TEST is not a TEST. Only valid when checks and controls are present and repeatable. And we still are unclear as to what "standard" test method was used for the original test data to know if it is repeatable.
It was a joke B-String. Lighten up.
Of course, I would take a front row seat, if it happened.
Just pointing out the facts before it goes out of control
Maybe if everyone pays up for the print version, the extra cash would allow a trip?
I paid already this year.
Maybe if everyone pays up for the print version, the extra cash would allow a trip?
I paid already this year.
