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Bobby Dipole 4th November 2010 07:25 PM

Pre-amp output level question
 
I understand the input level to a pre-amp or integrated-amp should be "line level", and this is a well defined voltage. But what is the output level of a pre-amp? Is the pre-amp basically an attenuator, i.e. 0 dB with the volume control at max? Or does it have gain?

Bobby Dipole

Mooly 4th November 2010 07:57 PM

Good question...
Most line level preamps offer gain. You can look at the figures and do the maths but in practice most power amps need a preamp with gain. Some CD's are for example recorded at quite low level not making use of the full dynamic range available and you might struggle to achieve enough output with a preamp of gain =1.

If the power amp had an input sensitivity of say 100mv rms for full output then you would almost certainly be OK.

If the power amp needed say 0.775 or even as much as 2 vrms then you would have problems.

A voltage gain of 3 to say 8 or so is usually sufficient and I like to match as best as possible different sources so that they all have similar volume. I have a DAB tuner that subjectively is much "louder" than a CD player so I have a lower gain on that input. An old 1980's cassette deck or tuner might only put out 100mv or so anyway.

There's no right and wrong answer...

pieter t 4th November 2010 08:11 PM

Mooly,
Low recording levels mean that the recording engineer was using his brains.
All too often digital recordings are over-modulated causing the hard "digital" sound.
It has nothing to do with dynamics.
Low level recordings have more dynamic headroom; it's the difference between soft and loud signals what is important. Classical music, especially large scale, has generally more dynamic contrast than pop music.

Pieter

georgehifi 4th November 2010 09:58 PM

Quote:

Originally Posted by Bobby Dipole (Post 2354380)
I understand the input level to a pre-amp or integrated-amp should be "line level", and this is a well defined voltage. But what is the output level of a pre-amp? Is the pre-amp basically an attenuator, i.e. 0 dB with the volume control at max? Or does it have gain?

Bobby Dipole


If you connect your CD player directly to your poweramp and you have enough level (which 99% will) you do not need a preamp with gain.
Please do this experiment using a quite starting cd and have your finger on the stop button.

Cheers George

jitter 7th November 2010 03:49 PM

Quote:

Originally Posted by pieter t (Post 2354418)
Mooly,
Low recording levels mean that the recording engineer was using his brains.
All too often digital recordings are over-modulated causing the hard "digital" sound.
It has nothing to do with dynamics.
Low level recordings have more dynamic headroom; it's the difference between soft and loud signals what is important. Classical music, especially large scale, has generally more dynamic contrast than pop music.

Pieter

This is only partly true. Modern pop recordings are made to the best ability of the recording engineers only to get totally destroyed by the people making the final version for the masters. This is done on purpose and usually at the request of the artists. They want loud recordings, and that's achieved by heavy compression. This has everything to do with dynamics (in fact, most modern pop CDs get rid of them). It doesn't necessarily mean they're over-modulated (i.e. clipping the signal).

If you were to look at the waveshape in a sound editing programme on your PC, you'd probably see a lot of variation between soft and loud passages on classical music and to a lesser extent that of older pop recordings. Now look at the shape of a modern (ca. 1995 and on) pop song...almost no variation.

Do a search on Google using the term "loudness war"... Chances are the no. 1 hit is a 2 min. YouTube film on this phenomenon.


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