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General debate thread about audio measurements

NorthSky

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maverickronin

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Is that at "normal" or "too loud" levels?

(I realize things go wrong when you run out of steam)
It really depends on the headphones. Impedances and efficiencies are all over the map. Impedance can be from single digit speaker territory to peaks above 1200 ohms. Efficiencies I know of range from ~76dB/mW to greater than 120dBmW.

"Too loud" with one headphone can easily be completely inaudible with another.
 

amirm

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Is that at "normal" or "too loud" levels?

(I realize things go wrong when you run out of steam)
For mild levels of distortion, no. But for the extreme THD with high power amps, I can only do it for a 5 seconds or so before worrying about my hearing. :D

In general, headphone amps run out of power far more easily than speaker amplifiers. Part of it is due to very high impedance of some headphones which reduces the power substantially.
 

amirm

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How much distortion a volume knob from a high grade preamplifier adds to the music playing when you move that knob and leave it where the volume level sounds right?
Do you mean with passive or active pre-amp Bob?
 

NorthSky

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Nothing specific Amir, just an overall volume pot we all have on our preamps, integrated amps, receivers, headphone volume control from headphone amps, laptops, tablets, etc.

Some I bet are cleaner, introducing less noise, distortion. That was my main point.
The picture and the link are just an example. When I was searching for a high end volume pot, I had a different one in mind, one that you posted in the past, and expensive too, very, this one ($1,000) came up in that search, and I found it pretty, simple, nicely built, relatively down-to-earth priced. ...But without any more than that.

Is active preamp better than passive?
 

RayDunzl

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Go buy a Fisher Price one for five bucks on eBay
I used a couple of 10k potentiometers between the CD player and power amp for a long time.


1536352808485.png


Cost about $5 for connectors and scrap cable and the pots and a piece of wood and some scrap metal to mount the pots.

I thought it was just fine, still would.
 
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RayDunzl

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Why don't you use them anymore, Ray; you found better ones, cuter, less noisy, ...?
It still in use, in another room.

Because I wanted additional functionality to comfortably accommodate hardware sources and destinations beyond a single CD player and power amplifier?

1536361615093.png


What noise?

A meter of cable with a resistor divider (pot) operating at line levels doesn't provide much opportunity for noise pollution at audio frequencies.
 

NorthSky

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Alright, how loud are we listening to, where on that dial are we turning up that volume control knob (potentiometer, volume attenuator)? How much break pedal (attenuation) are we releasing? What resistance is applied say when we are using normal power...less than 3 watts RMS? @ what average level are we listening to our music? What is the meter showing...0.3 watts? ...Little bit more...1.0 watts? It depends, passive or active listening...background music or front end serious music.
...From a normal stereo preamp, from a headphone amp.


@ low volume level listening we usually measure larger amount of THD.
And the more we crank the volume up the distortion level decreases, up to the power amp limit, where the distortion rises abruptly and clips.
With a quality amp the level of THD is low from 0.001 watts to say 5 watts.
Some amps have larger level of THD @ very low power...say less than 3 watts.

Using a quality amp, how much influence a volume pot can have on the sound output...measurable distortion level? Are there better potentiometers with less measured distortion, and if yes, what are the best ones and why are they measuring better?
 
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RayDunzl

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Alright, how loud are we listening
Right now?

TV News through the little JBLs.

1536365593880.png


The maximum measured peak using the mains was 116.9dB on a short snippet of drums (just testing). Sounded dangerous to me.
 

Wombat

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Rrrrrrrrrrr
Go buy a Fisher Price one for five bucks on eBay. :p
Post #391 above is all that is needed. Put in a box it should sell for somewhat less than $50.
 

RayDunzl

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Ray, that's not your daily average loudness level?
116.9dB - no, that was a calibrated experiment, with one of Mario Martinez's (inactive member) files using the Krell amps and MartinLogans.

Is that from your speakers or your headphones?
Graphic Above? It's the JBL speakers.

It's a reasonable level for all day casual listening.

Another sample:

TV still running. No EQ, so some 100Hz room hump is evident. Content is the Smithsonian Channel, investigating if some Egyptian hieroglyphics explain the 10 plagues mention in the Bible (and commercials):

1536372451979.png
 

NorthSky

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You got some 9/11 history channel with the latest cancer dead people and the next to come in the future. Adjust the volume for a comfortable voice level, and then measure. • https://www.msn.com/en-ca/health/me...that-fateful-day/ar-BBMX459?OCID=ansmsnnews11

To reach 67dB how many watts is that? ...From your own system's volume knob (pot), which position on a clock would that be? ...Ten o'clock...roughly?

* Is your volume control analog or digital?
 
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