Question I don't understand pre-amps and power-amps. Please explain.

DartonDave

Standard Member
Hi all. Very infrequent poster here. I am hoping someone can explain to me how pre-amps and power amps work. I will forgo all the background as to why I am asking but understand I'm not looking to buy now (famous last words I know). Also the title is a bit mis-leading as after reading some stuff on the internet I get that you have an AV pre-amp which has HDMI inputs for your sources and then outputs (RCA but also XLR on better models) for each "channel" (eg front left speaker, front right speaker, etc). The RCA or XLR cable connects from the pre-out on the pre-amp to the corresponding input on the power amp. Speaker cables then go from power amp to the actual speakers. Only exception seems to be subwoofers which go straight from the pre-amp to the sub or subs. All easy and straight forward so far.

So I took the anthem amps as an example (probably because it will be a leading contender for my next amp) I looked at the back of the AVM-70 and there are 17 pre-out connections in both XLR and RCA. That includes 6 height channels and 2 subwoofers, so in theory you could have a 9.2.6 system if you so wished from this one pre-amp.

I then looked at the matching power amp in this case the top of the range MCA525 which can cater for the standard 5 set up in a 5.1 system! So I thought ah....I must have to buy another power amp if I had a 7 .1 / 7.2 or some other configuration. What if I wanted to push the boat out and have a 9.2.6 system? The pre-amp has all the pre-out connections I assume I must have to keep buying power-amps until I have enough???
The MCA225, 325 and 525 are all setup for the standard 2 (stereo), 3 (front 3) and 5 (front 3 plus 2 rears) channels and not anything more. I'm now confused. I have a pre-amp but can only attach 1 power-amp? That cant be right.
What's the point of all those pre-outs if there isn't a power-amp with a matching channel config?

If you look at the back of the integrated MRX1120/1140 that can feed 11 channels with the option of using 4 pre-outs for a separate what I assume is a power-amp? But which one would you use?

So the integrated solution can cater for more speakers than the separates solution? That cant be right either.

What is it I am missing?
 

Marvin the Android

Well-known Member
Using more than one power amp?
 

rccarguy2

Well-known Member
Correct you may need more than one poweramp. Ie In stereo you'll need two, 5. 7.1 etc
I've seen 12 channel poweramp

The issue is power and size you won't find a 12 channel 200w per channel and it'll be huge and require two mains inputs

I'm using two multi channel amps if the want to go Atmos I'll need a four channel amp
 

DartonDave

Standard Member
Correct you may need more than one poweramp. Ie In stereo you'll need two, 5. 7.1 etc
I've seen 12 channel poweramp

The issue is power and size you won't find a 12 channel 200w per channel and it'll be huge and require two mains inputs

I'm using two multi channel amps if the want to go Atmos I'll need a four channel amp

Thanks very much for the prompt response. but I'm still not fully getting it. Im sorry.

Lets say I want a 7.2.4 system (I don't atm but may well do in the future) what do i buy and what plugs into what?

I can see how i can set up a 5.2 system using the AVM70 pre-amp and a MCA525 poweramp (5 channels labelled front right, front left, centre, rear right, rear left).
So would I need another 4 channel amp and a 2 channel amp? 5 + 4 +2 = 11,
And 7 + 4 = 11

I then ignore the labels on the back of the amp and configure it to what is coming out the pre-processor?

Sorry if Im sounding thick. Never looked into non integrated amps before.
 

Jase

Distinguished Member
Thanks very much for the prompt response. but I'm still not fully getting it. Im sorry.

Lets say I want a 7.2.4 system (I don't atm but may well do in the future) what do i buy and what plugs into what?

I can see how i can set up a 5.2 system using the AVM70 pre-amp and a MCA525 poweramp (5 channels labelled front right, front left, centre, rear right, rear left).
So would I need another 4 channel amp and a 2 channel amp? 5 + 4 +2 = 11,
And 7 + 4 = 11

I then ignore the labels on the back of the amp and configure it to what is coming out the pre-processor?

Sorry if Im sounding thick. Never looked into non integrated amps before.

As mentioned, you just add as many poweramps as you need. Whether that be monoblocks or 2CH, 3CH, 5CH, 7CH etc etc. It generally doesn't matter how their channels are labelled as they'll just amplify whatever signal they're fed.

An exception to this would be a poweramp that has channels with less power than some of the others. In that scenario you'd usually use the highest powered channels for your Left, Right and Centre and the others for Surrounds or Heights. All depends on what poweramps you're using and your speakers.

AV Receivers also have pre-outs so you can beef up the amplification to your speakers or if you want to expand the amount of channels in your system. Several AVR's can process more channels than they have amplification for so that's where you'd need a poweramp. The Anthem MRX1140, for example, can process up to 15ch but only has 11ch of amplification built-in. Hence the need for pre-outs.

Looking at the specs to determine how many channels an AVR or Processor can process is key as that will dictate how many extra poweramps you may or may not need.
 
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