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Old 3rd July 2007, 02:25 PM   #1
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Default Does preamp wattage effect power amps wattage?

If my preamp has 5 watts of output and I run it into a 100 watt amp, will the 100 watt amp produce more wattage?

I have a couple setups like this but they have always run safely. I can't really say I notice a volume increase with these high output preamp setups but they surely sound fuller on the speaker end of it all.
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Old 3rd July 2007, 02:47 PM   #2
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I'm not an expert on this so take my words with care, but anyway:

Preamps have 2 uses: 1. have high input impedance to reduce stress on source and low output impedance. 2. yield the same output voltage level for all sources (which in general have different output levels, compare phono pre with a cd-player for example) ; of course this includes attenuation.

So there is besides voltage amplification no amplification at all. Hence the power rating of the pre is completely pointless and leads in no way to higher power of the power amp.

The only influence I can imagine is that the output level of the pre is too high for the power amp and it starts to clip. Not a nice feature at all.

Cheers, Hannes
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Old 3rd July 2007, 02:53 PM   #3
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I can't get my head round a pre-amp having 5 watts output. As said they are line level buffers with no power output to speak of.

Where did you get this rating from? The power consumption on the label is not the amps power output!
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Old 3rd July 2007, 03:01 PM   #4
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Default Re: Does preamp wattage effect power amps wattage?

Quote:
Originally posted by 1400WATTSRMS+
If my preamp has 5 watts of output and I run it into a 100 watt amp, will the 100 watt amp produce more wattage?

Good questions!

The preamp power will not effect amplifier power.
Preamps are designed to provide a voltage level to the amplifier, and deliver whatever power level is needed to maintain that voltage.

100 or 105 watts wouldn't make any difference to the sound anyway.

A 100 watt amplifier will not be putting 100 watts into the speaker either under normal circumstances.
It'll average closer to 3 or 4 watts.
The 100 watt rating allows you to compare similar amplifiers and their chances of distorting the sound (clipping in this case) during brief, extra loud bursts of sound (like a soundtrack 'explosion' or maybe a loud drumbeat).
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Old 3rd July 2007, 03:09 PM   #5
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Your power amp has a Voltage senstive input (not Watt sensitive input). Most power amps produce max output power at 0.7 Volt input, and as the input impedance mostly are 20K or more, your preamp has to deliver 0.035 mA = a total of 0.0245 mWatts
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Old 3rd July 2007, 11:51 PM   #6
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I am using a very small amp that produces about 3-5 watts as a preamp into a push/pull amp that can push 90 watts RMS into an 8 ohm load.

ACD from what I understand, wattage in some circumstances can serve the same purpose as voltage well dealing with audio sourced signals.

It really enriches and just beefs up the sound. The small amp has a preamp gain and master volume. I generally never have both dials past 60-70% but on some occasions do. Has worked flawlessly this way for several years so I built the same hop up for a couple smaller amps that have yielded the same results and after a couple years of use, no problems.

I imagine I'm just reeking the benefits of very clean high gain unorthodox preamp set up. Regardless of extreme long term use results, I have no intentions to change a thing.
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Old 4th July 2007, 01:46 AM   #7
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Hi 1400WATTSRMS+,
Quote:
I have no intentions to change a thing.
Cool. It's your rig.
Quote:
I am using a very small amp that produces about 3-5 watts as a preamp into a push/pull amp that can push 90 watts RMS into an 8 ohm load.
What you are hearing is the extra distortion from the small amp. A proper preamp would produce less distortion (I hope!) and would have less ...... "character" shall we say?

Enjoy!

-Chris
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Old 4th July 2007, 03:18 AM   #8
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Quote:
Originally posted by 1400WATTSRMS+
ACD from what I understand, wattage in some circumstances can serve the same purpose as voltage
They are inextricably connected but the input to an amp is generally an arbitrary fixed resistance so talking about it in the power domain (Watts), makes little sense.
Quote:
I imagine I'm just reeking the benefits of very clean high gain unorthodox preamp set up.
One of the characteristics of an amplifier is that generally it isolates the input from the output. How you drive the input to the 90W power amp then has almost nothing to do with its output stage driving the speaker. What can possibly be an issue is how the input to the 90W amp loads the output of the pre stage but this is a relatively problem free issue.
Quote:
It really enriches and just beefs up the sound.
I agree with anatech, this almost certainly comes from the character of the first amp you use. In other words distortion, but if you like it then OK.
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