Is 0dB considered "reference level"?

[sfogg]

"that showed the approximate output at each detent level for the
nominal "test" load. Pre-out and main-in sensitivity is 700mV at
100k-ohms; nominal input into the pre is 130mV. Power RMS is rated 110
wpc, but I just had one of the 11000's rebuilt. According to the tech,
Warren Bendler (www.sansui.us), the amp tested out at 115 wpc + 0.05 watts into an 8 ohm load at 1khz (which is apparently the factory method of testing on the bench).Knowing
that... and not using any controls except the volume control, how do
you calculate the power that it would be producing for each detent?"

You
can't really tell this easily since it will depend upon what the input
voltage is and of course different analog sources may output differing
voltage levels. That is what is nice about digital inputs into
receivers/pre-pros... that max they can put out is the same for all
sources(0dBfs). It isn't as neat and clean in the analog domain.

Shawn

[sfogg]

"so any of these dB markings can not tell you a thing about how much
power the amp is putting out. It's not even relative. You can't say,
"the output is 20dB less than full power" because the input voltage has
no reference. So, the usefullness of putting a dB scale around the ring
of a volume control is pretty much limited to the "pizazz" factor, and
not much else. "

Mark,

If the dB markings are accurate (and they very well may not be on a
unit with a pot in it) those markings are still relative. If you turn
the volume from -20dB to -30dB you have decreased the average and peak
SPLs by 10dB. Likewise you also know the amp is putting out 1/10 the
power then it was before. What it does not tell you is an absolute
number for how loud the peaks could be or absolute metric for power
output.

Shawn

[Groomlakearea51]

I am looking for a "relative" method, per se. Given only 130mV at 1khz (which the tuner has a switch to do that), and given the sensitivity 700mV. Better question... Given only those parameters... and 0dB is 115 watts, how would you calculate down to -70 (or infinity or full suppression? What's the simple formula? "For every decrease of 1dB, there is a corresponding decrease of ???

[Groomlakearea51]

Or.... I have a measurement device. At 0db, 1khz signal, 130mV input; 700Mv sensitivity between pre and main, and amp is making 115 wpc; what would the amp be making at -42dB (assuming all else remains equal)

[sfogg]

Roughly

3dB increase is 2x the power

10dB increase is 10x the power

Likewise 3dB decrease is 1/2 power

10dB decrease is 1/10 the power

Shawn

[sfogg]

115w 0dB

11.5w -10dB

1.15w -20dB

.115w -30dB

.0115w -40dB

.00575w -43dB

Shawn

[Groomlakearea51]

That would explain why at -24dB in the man cave with the Klipschorns... dogs and cats are running away, livestock falling down, women and children cowering, etc., etc. Peak, interestingly, at -24 has pegged at well over 100 watts on certain songs.... Amp is fine as it has a massive toroid power supply and can sustain peaks up to a rated 585 watts.

Is this formula derivation then correct.

NOMINAL VOLUME CONTROL SETTINGS	POWER @1KHZ, 130Mv INPUT, W/700mV SENSITIVITY
0	115.00000
-3	57.50000
-6	28.75000
-9	14.37500
-12	7.18750
-15	3.59375
-18	1.79688
-21	0.89844
-24	0.44922
-27	0.22461
-30	0.11230
-33	0.05615
-36	0.02808
-39	0.01404
-42	0.00702
-45	0.00351
-48	0.00175
-51	0.00088
-54	0.00044
-57	0.00022
-60	0.00011
-63	0.00005
-66	0.00003
-69	0.00001

[Groomlakearea51]

I guess it must be so.... LOLOL!!! The service manuals don't refer to that gain, but then again they are 30+ years old. Is that gain level between pre and main a "normal" gain by solid state standards back then?

Shawn/ Mark: I'm good at wood..... but now I'm learning something as to how those pretty cabinets make the sounds!!!!

[laager]

Why be caustic and unecessarily argumentative? It doesn't make sense.

I'm not being caustic, simply requiring justification for the entirely subjective interpretation of the question's terminolgy. Just because I don't blindly take someone's opinion as gospel doesn't mean I'm argumentative.

"if a receiver is not 'THX certified' then the calibrated 0dB = 'THX Reference Level' argument falls to pieces "

Not in the least. If one calibrates the unit as I said above it makes no difference if the receiver is THX certified or not. It will still be calibrated such that 0dB on the volume control is THX Reference level. ... One can calibrate *anything* to THX reference level, even a basic 2 channel pre-amp.

Sorry, but if you cannot actually calibrate the unit to the level you suggest, 0dB will still be shown on the receiver. There will be some receivers that no matter what they are connected to will not produce the calibrated level 105dB 'THX Reference Level'. Hence, are you arguing that those receiver's manufacturers are being deliberately deceptive; or willing to admit that 0dB on the receiver is an entirely arbitrary point on a scale which is selected by the manufacturer?

Which leads back to the original premise that your assumption as to the OP's terminology may be incorrect, as may be mine, but to deny the possibility of this would be somewhat pretentious.

[sfogg]

"There will be some receivers that no matter what they are connected to
will not produce the calibrated level 105dB reference level you insist
upon."

It takes between about 3 to 10w or so to do this on a K'Horn in a home. How many receivers do you know of that can't put out that much power?

And I already stated that this isn't taking into account running out of power or power compression in the speaker itself. Even if the combo can't hit the peaks the average playback level will still be proper at THX Reference Level. Average level is about 85dB at the listening position. Still THX reference level playback, just can't hit the peaks.

"Hence, are you arguing that those receiver's manufacturers are being
deliberately deceptive; or willing to admit that 0dB on the receiver is
an entirely arbitrary point on a scale which is selected by the
manufacturer?"

Neither.

There is nothing deceptive about that scale and it is also not entirely arbitrary. You do realize of course the speaker level trim is in essense a second individual volume control for each channel in the receiver don't you? Most have at least 20-30dB of range relative to the master volume control (the 0dB on the scale). The process of calibrating the receiver is using those speaker trims to dial in the levels properly which makes the master volume control calibrated and anything but arbitrary.

Shawn

[sfogg]

"Average level is about 85dB at the listening position. Still THX reference level playback, just can't hit the peaks."

BTW, should point out that average level is based on movie playback where movies are mixed to be played back at reference level and mixed to preserve dynamic range. On any overly compressed music of today where louder=better the average playback level would be much higher but still limited by that 105dB maximum due to 0dBFS.

Shawn