[Arny Krueger]

"Eeyore" wrote in
message

Arny Krueger wrote:

"Eeyore" wrote:
Arny Krueger wrote:
"Eeyore" wrote

So what's the THD of your QSC USA amplifier @ 100mW /
~ 900mV with a speaker load ? That's YOUR reality.

I rummaged around and found some test data I took some
years back at a power level of 1 watt into an 8 ohm
resistive load.

Test 1: sine wave test with 1 KHz tone.

Stimulus 1 was 1 watt @ 1 KHz into 8 ohm resistive
load:

All harmonics through approx 40 KHz were 96 dB or more
below 1 watt.

In that case your test was defective.

On what grounds?

No grounds provided other than a gut feel.

That you disagree with the results?

On the grounds that I know it to be 100% implausible.

I believe that you're using the resolution of the controversy to judge it.
That's a fallacy, you know.

I'd be stunned if I could design a low-cost commercial amp
that good quite frankly and I know that Pat Quilter's no
better at it than I am.

Show me your evidence.

How low can you go?

I didn't actually say that to YOU because I was being
nice but you really do need to revisit your test methods.

Been there, done that.

The numbers you quoted suggests to me that there was no
load attached.

Not a chance.

The tests were done as follows. We tested 5 amplifiers, at 4 power levels,
with two different loads. We tested each amplifier 5 times. The first test
of each group of 5 started by playing back a 3 minute sequence of test
signals, both test tones and music, and recording the output of the
amplfiier. A 1 KHz test tone at the same level as the peak level of the
sequence was used to set the operational level at the beginning of each
test. The peak level of the sequence as played and recorded was 1 dB below
FS of the recording and playback equipment.

The sucessive 4 additional tests in each group were performed by feeding the
output signal from the previous test into the next one.

The recording and playback was done using a LynxTWO under the control of
CoolEdit 2.1 running in 32 bit 96 KHz multitrack mode. The LynxTWO was
running in 24 bit mode.

What I have today are the recordings of the input and output signal. I found
them on some old hard drives that I archived.

The power levels were 1 watt, 10 watts, 100 watts, and a "full output" level
that we chose on the spot to correspond to a nice round number that was
below clipping throughout the test sequence.

The two test loads were a resistive load composed of NI wirewound resistors,
and a reactive speaker load simulator that I have documented many times in
many places including both of my web sites.

By the time we tested each amplifier at its "full output" level, we were
definately straining the infrastructure. The 2 KW line conditioner was
humming loudly, and the test loads were more than a little warm. Becase of
the way we did the tests, the actual duration of the high-powered sine wave
tests was only a few seconds so nothing broke and no breakers tripped. The
speaker simulator was by far the easist load for any of the amplifiers to
drive.

The bottom line is that there was no doubt in my mind that the amplifiers
were tested under load. By the end of the test all we had to do is put our
hand a few inches over the load to know which one we were using! ;-)

Maybe you'd like to try the test again ?

What, and subject myself to more baseless redicule? ;-)