[Arny Krueger]

"Eeyore" wrote in
message
Arny Krueger wrote:

"Mr.T" wrote
"Eeyore" wrote

To elaborate, the cross-over region introduces a highly
non-linear 'kink' into the transfer characteristic of
an amplifier at exactly the audibly most critical
point. No amount of obfuscation can deny that basic
fact. The smartest techniques to ameliorate the
situation include 'moving' the kink away from the zero
signal region by various methods and 'stretching' the
kink so its effect at any given level is reduced.

And yet many modern amplifiers when properly measured at
1W (regardless of max power rating, and price) still
exhibit miniscule levels of THD and IMD. The theory is
correct, but not necessarily a real problem.

I suspect that Graham and the last AP test set he ever
used have been separated for some time.

Only about a year. I'm working on fixing that too !

Me, I never had one, but figured out how to fake it
with really good sound cards. A fairly mediocre one in
the right hands could educate the man about modern
reality.

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.

Test 2: a standard dynamic range test signal ( 1 KHz test tone 60 dB below
FS = 1 watt)

Stimulus 2 was 1 KHz tone at 60 dB below FS = 1 watt. If FS was 1 watt,
then 60 dB down would be 1 microwatt, right?

All harmonics were 114 or more dB below FS. IOW 54 or more dB below the
test tone.

Actually, there was nothing I would properly call a harmonic. The baseline
was all noise or hash.