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Old 3rd February 2012, 12:14 AM   #11
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Quote:
Originally Posted by Antoinel View Post
The plus sign signifies no inversion of the signal phase.
No - it signifies gain, as opposed to attenuation. Try to take the log of a negative number...

As already mentioned above the gain should go with the power of the amp, assuming some sort of standard for input signal and speaker impedance.
So higher power amps need more gain than lower power amps in order to fully utilize the power of the amp.
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Old 3rd February 2012, 03:09 AM   #12
jcx is offline jcx  United States
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yes the question is sideways to the real issues

you want to know what is the avaiable input V from your source, or what is the "standard" consumer line V level

then you want to know ranges of source material recording levels and if that implies a need for more system gain

then with amp supply V/power rating you can determine gain - if it sin't already limited by stability concerns (chip amps)


unusual speaker sensitiviy can also change the equation since what you really want is proper "gain structure" to avoid noise, give adequate volume, range of SPL at the listening position

Last edited by jcx; 3rd February 2012 at 03:34 AM.
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Old 3rd February 2012, 03:20 AM   #13
AKSA is offline AKSA  Australia
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THX standard is 29dB (Av=28.5).

Hugh
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Old 4th February 2012, 08:49 PM   #14
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Thanx guys!!!!
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Old 9th February 2013, 12:17 PM   #15
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by AKSA View Post
THX standard is 29dB (Av=28.5).

Hugh
Hi Hugh

What should be the standard gain for a pre amplifier ?
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Last edited by RCruz; 9th February 2013 at 12:22 PM.
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Old 9th February 2013, 12:28 PM   #16
lineup is offline lineup  Sweden
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Quote:
Originally Posted by RCruz View Post
Hi Hugh

What should be the standard gain for a pre amplifier ?
There are many preamplifiers with +12dB gain.
This is same as x4.
We can say sort of a standard is x4 = +12dB
but of course there can be other gain.
So, x10 is sometimes seen in preamplifiers.
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Old 9th February 2013, 04:22 PM   #17
DF96 is offline DF96  England
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I guess x4 (12dB) is a good value. Preamp gain needs to be low. In most cases it only needs to be around x1 (0dB), which means either no preamp or a genuine buffer to make up for weaknesses in other components. x2 (6dB) is hardly worth bothering with, as it won't sound much louder than x1. So x4 (ish) is the smallest number above x1 which is worth doing. Going higher than x4 is almost always a mistake, as you are merely amplifying a signal in order to attenuate it again - only worth doing if you like your music with unnecessary noise and distortion.

So the sensible choices are:
(a) no preamp
(b) genuine buffer (x1, 0dB, high input impedance, low output impedance, low noise, low distortion).
(c) x4 (12dB) or thereabouts
Curiously, most people who wish to avoid (a) either go for an FX box calling itself a buffer, or far too much gain so have to add attenuators.
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Old 9th February 2013, 04:52 PM   #18
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That looks like Nelsons thoughts with the B1. For those that don't know the B1 it is a unity gain ie gain=1 buffer amp.

Even my mighty Pass Aleph 4 with only 15dB of gain needs only the output of a standard CD player to drive it to its maximum. I could use just a passive pot but I choose to use a B1 to match all the impedances together. And it works an absolute treat.

Last edited by KatieandDad; 9th February 2013 at 04:55 PM.
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Old 9th February 2013, 06:43 PM   #19
wahab is offline wahab  Algeria
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Quote:
Originally Posted by KatieandDad View Post
That looks like Nelsons thoughts with the B1. For those that don't know the B1 it is a unity gain ie gain=1 buffer amp.

Even my mighty Pass Aleph 4 with only 15dB of gain needs only the output of a standard CD player to drive it to its maximum. I could use just a passive pot but I choose to use a B1 to match all the impedances together. And it works an absolute treat.
15db gain is enough for a moderate power amp but for 100W/8R (28V RMS)
for instance it s somewhat short.
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Old 9th February 2013, 07:23 PM   #20
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It works beautifully,.
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