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Preamp out to power amp question

S

surfinthetao

New Member
Hello, longtime lurker here. Hope I'm posting my receiver pre-out and power amp questions in the right place. I want to hear the sound of the power amp, and use a receiver as a volume control for incoming computer audio, and possible hook up two sets of speakers at once. the power amp has connections for one 8 ohm speaker pair. The receiver has connections for a front and rear 8 ohm speaker pair. Both sets of speakers I have are 8 ohm.

I noticed in my receiver manual (HK3250) , it says the PRE OUT rca s are for connecting to a power amp if you want the power amp to power the speakers. Does this mean I can have the power amp turned on without using the power amp's own speaker connections? And just connect the speakers to the HK3250 receiver? I've heard it was bad to turn on an amp without speakers connected so I want to make sure I do this right.

If I want to use 2 sets of speaker pairs, is there ever a reason to use the speaker connections on the receiver and the power amp if that's possible or preferrable?


Equipment
M audio Audiophile 192 computer sound card with 1/4 monitor and main outs running into 1/4 to rca cords.
Harman Kardon HK3250 receiver 40w/channel
Harman Kardon PA2100 power amp 65w/channel
ADS L420 speakers
ADS 1090/2 speakers
 
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The pre-out connections are for feeding into a different power amp. The 3250 will give you volume, tone, and input control and your external power amp runs your speakers. If you set it up this way, the 3250 doesn't need to have speakers connected to it. The speakers would connect to your PA2100.
 
SS amps can be powered up without speakers (or a dummy load) attached. Tube amps should not be operated w/o speakers attached. You can connect your power amp to the receiver pre-outs to feed signal to the power amp, and attach speakers to it. You can run speakers from both the receiver and the amp in this configuration, but the gain/volume level between the speakers being driven with two different amplifiers (one external and one internal on the receiver) may not be anywhere near close.
 
savatage1973 said:
SS amps can be powered up without speakers (or a dummy load) attached. Tube amps should not be operated w/o speakers attached. You can connect your power amp to the receiver pre-outs to feed signal to the power amp, and attach speakers to it. You can run speakers from both the receiver and the amp in this configuration, but the gain/volume level between the speakers being driven with two different amplifiers (one external and one internal on the receiver) may not be anywhere near close.
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I do believe you're mistaken regarding this.

Using the preamp outputs will not allow the use of speakers attached to the receiver.

Unless the amp has a 'loop output'....and you run interconnects back to the 'amp in' jacks of the receiver.
 
BigElCat said:
I do believe you're mistaken regarding this.

Using the preamp outputs will not allow the use of speakers attached to the receiver.

Unless the amp has a 'loop output'....and you run interconnects back to the 'amp in' jacks of the receiver.
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It depends on the receiver or integrated amp. If it uses jumpers for pre-out/main-in, then you will need a splitter cable to use both the internal and outboard amp, but I have a couple integrateds that have dedicated pre-outs that you can just hook up to an external amp and still use the internal amp at the same time without doing that. I am not specifically familiar with the receiver in play here, but if it has a separate pre-out, you should be able to use both the internal amp and the external amp simultaneously.
 
So, the real question is "Does the Harman Kardon HK3250 receiver continue to feed signal to the receiver speakers when the pre-out connections are in use?"

A look at a picture of the rear panel shows a pair of pre-out RCA's - and no 'power amp in' sockets or a switch - so maybe that's an indicator that it does feed the receiver connected speaker set even with the pre-out RCA's in use?

Any thoughts on this?
 
Hmmm...

The HK 3250 has pre-outs, but no amp in jacks. I have a HK 3370, it has classic pre-out / amp in jacks.

I guess I don't understand the OP's question. If he hooks the PA-2100 to the pre-outs, of course he'd have to connect speakers to the PA-2100.

Why else would he use the PA-2100 ?
 
If the PA2100 has gain controls/input attenuators then connecting a pair of speakers to the receiver speaker sockets AS WELL is a possibility, otherwise I would say not a good idea - unless there is a feature on the HK that I am not aware of (easily could be :)).
 
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If there are no MAIN AMP input jacks but there are PRE output jacks, chances are the signal continuity to the receiver's amplifier section is maintained. That would be my guess unless the owner's literature states otherwise.
 
62caddy said:
If there are no MAIN AMP input jacks but there are PRE output jacks, chances are the signal continuity to the receiver's amplifier section is maintained. That would be my guess unless the owner's literature states otherwise.
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So what happens if he uses the receiver without speakers hooked to it ?

As a pre-amp only ?
 
Thank you so much for the replies. The discussion is really interesting and answered my questions. I will get the amps in about a week and test the 1090/2 hooked up to the pa2100 alone, and with the L420's on the Hk3250 just for fun and see if it works .
I was previously thinking if I only used the speaker connectors on the HK3250, it might allow for the power amp to power the 4 8 ohm speaker connections on the HK3250.

So the main in option on receivers (which my hk3250 doesn't have) would be to run the receiver as a power amp and be able to bypass the preamp of the reciever?
I was thinking about running the power amp direct from my sound card, but my main concern was having the volume be up 100 percent on my computer and blasting my speakers too loud by accident, so I wanted a real life volume control knob.
 
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surfinthetao said:
So the main in option on receivers (which my hk3250 doesn't have) would be to run the receiver as a power amp and be able to bypass the preamp of the reciever?
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Yes, if a receiver or integrated amp has pre-out and main-in jacks on the back (usually connected by a jumper or an associated switch nearby), you can use it as just a power amplifier, supplying the input signal from another source, bypassing the preamp section. It works three ways--you can use the preamp/tuner only, the power amp only or the two together as designed. Lots of people pull the jumpers and use just one section. I am more of a "separates" guy where everything is its own "box", but you have the flexibility to do this with receivers/integrateds if they have the pre-out/main-in jacks.
 
Seems as good a place as any for this question. I've only ever used a receiver to power speakers. Presently I have an HK930 (45 wpc) for that job. Well, I got some bigger speakers and would like to feed them a little more power. So, if I hook up a power amp to the 930 then the receiver becomes the preamp essentially? Any answers to my noob questions would be greatly appreciated. Thank you.
 
DavidJB said:
Seems as good a place as any for this question. I've only ever used a receiver to power speakers. Presently I have an HK930 (45 wpc) for that job. Well, I got some bigger speakers and would like to feed them a little more power. So, if I hook up a power amp to the 930 then the receiver becomes the preamp essentially? Any answers to my noob questions would be greatly appreciated. Thank you.
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Yes. Remove the jumpers between preamp outputs and the main amp input jacks on the rear panel of the HK930 and connect the outboard amplifier to the preamp outputs of the HK930. Usually advisable to place shorting plugs at each of the main amp input jacks which will prevent the amplifier from responding to any unwanted signals/noise/hum as a result of the inputs being "open".
 
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