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Old 10th February 2013, 10:05 AM   #31
JMFahey is online now JMFahey  Argentina
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No, you can add gain, if it' a logarithmic scale, such as dB.

But in your case you are using gain factor (Vout/Vin) so you should multiply them: 30 x 16=480x
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Old 10th February 2013, 10:29 AM   #32
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Quote:
Originally Posted by tinitus View Post
and this is part of the reason why bigger power amps usually have many more devices in the preamp/driver stages ?
A related offshoot question... for an amp in the near kW range and above, how many voltage gain stages would a person be likely to find inside? Just two or three, or more likely a half dozen?
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Old 10th February 2013, 10:41 AM   #33
RCruz is offline RCruz  Switzerland
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I am sorry, I meant 16dB gain for the preamp and 30dB for the power amp.

So total gain would be 16 + 30 = 46dB (199x)
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Old 10th February 2013, 11:02 AM   #34
tinitus is offline tinitus  Europe
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Maybe, but not necessarily.
In general they add more devices to make the amps symmetrical, or use CC loads instead of plain or bootstrapped resistors, more linearity, better phase characteristics, less distortion, etc.
yes, we know that
I would have asked...more than just one gain stage...but also knew that probably wouldn't make much sense either but made my question sound stupid i the end
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Old 10th February 2013, 11:15 AM   #35
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Hey, are you saying my question doesn't make sense, or sounds stupid?
Really, I just don't know and am curious. I'll find out one way or the other.
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Old 10th February 2013, 12:32 PM   #36
tinitus is offline tinitus  Europe
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Originally Posted by sofaspud View Post
Hey, are you saying my question doesn't make sense, or sounds stupid?
quite the opposite
I thought your question supported mine, and along the same lines

hell, in another thread I read that it can be argued if even a ccs can be a gain stage
well, half of mu-stage is a ccs, no ?
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Old 10th February 2013, 03:05 PM   #37
JMFahey is online now JMFahey  Argentina
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Well, to answer sticking to the point: no, you don't *need* extra gain stages at all.
A 100W/8 ohms amp needs to supply 28V RMS , so needed gain for 1V sensitivity is 28/1=28x=29dB
A1000W/8 ohms amp (not many of those around there) supplies 3.16x that = 88.5V RMS, or 10 dB more.
Since a common open loop gain for simple classic garden variety Lin Amps hovers around 60/65 dB , same gain structure offers more than enough gain for both, without extra stages.
Simply the 1000W amp will have 10dB less NFB , so it will show higher distortion, less extended frequency response, etc.
But it will still be very usable.

Now, if you want to polish that basic design, the Sky is the limit.
But be aware that any extra gain stage (doubt you can add more than one) will compound compensation, phase and stability problems.
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