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Author Topic: How to match a preamp with a poweramp?  (Read 5092 times)

SDRed

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How to match a preamp with a poweramp?
« on: October 27, 2007, 04:56:51 PM »
Hi everyone, this is my first post here and I'm excited about this forum, I've been reading all I can trying to learn since I've recently started in this addicting hobby.  These questions may be common sense to some, but since I'm new to this and so are others who are searching this forum for answers, I thought some explanation would be most helpful.

My question is about knowing how to hook up a preamp to a power amp and how to power both.

Correct me if I'm wrong:
1.  It isn't as simple as connecting the preamp out to the amplifier in.  There has to be some match in resistence?  If so, how does one go about calculating that.

2.  How are both preamp and poweramp typically powered together.  Does each have its own transformer that are hooked together somehow?  Do they both run off the same power supply?

3.  For my next project, I'd like to use one of the ROG emulators as a pre with an amp on the GGG site.  I know that some other posters here said that they were also going to attempt such feats, but I have not read of any success stories.  Keep in mind I don't want this to be an external preamp, I'd like it to be all one unit.

and Lastly if the preamp is usually running on 9v and the amp is made to run on 18v bipolar power, can the 18v bipolar simply power both? 

Thanks for whatever information you can give me, I look forward to your responses.

LJ King

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Re: How to match a preamp with a poweramp?
« Reply #1 on: October 27, 2007, 05:41:17 PM »
#0 - The first rule is that there are no rules.

#1 - Typically a power amp wants to see a line level signal to be driven to full output. This is usually a one volt level. What you are calling resistance is actually impedance, even though both are measured in ohms. A lower output impedance from the preamp with a higher input impedance for the power amp insures the transfer of maximum voltage.

#2 - refer to #0. There are examples of both. Generally, when cost is a primary issue, both will be powered from the same power supply.

#3 - Don't have a clue.

#(4) - Yes, lower voltages can be derived from a higher voltage supply. A stage of RC filtering, or zener, or a voltage regulator can reduce the higher voltage to a lower supply voltage.

SDRed

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Re: How to match a preamp with a poweramp?
« Reply #2 on: October 29, 2007, 01:09:21 AM »
Thanks,

I'm just about done with the preamp circuit and will start on the poweramp in the next couple of days.  My next question and this may sound stupid: do I run both pre and poweramp to the same ground, or does each need its own ground circuit?  I want to run them off of the same power supply so it seems to me that they go to the same ground right?


joecool85

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Re: How to match a preamp with a poweramp?
« Reply #3 on: October 31, 2007, 07:45:03 AM »
I ran mine on the same ground.  Some people have issues with that.  I would recommend running it on the same ground, then if you have noise issues go from there.  You should be fine though.
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LJ King

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Re: How to match a preamp with a poweramp?
« Reply #4 on: October 31, 2007, 10:03:29 AM »

With a single power supply there is really no choice but to have a common ground. Think of ground as the return path for currents back to the power supply (current always needs a complete circuit path, otherwise it don't flow).

 

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