How to Connect My Sub to My Preamp

Hello man

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Hi guys,

I just scored a Polk 8 inch 100W RMS sub for $12 at goodwill yesterday. However my receiver and amp are old Technics pro line gear. The preamp is a SU-9070, and the amp an SE-9060. Being old, they have no designated sub out. There are two possible ways that I can see to run the sub, but I need your expertise on this one.

I have the sub plugged into the "EXT Unit" output. Only problem is it stays at the same volume even when the volume is turned down on the preamp. Any ideas?

Here is the service manual. Second page shows the back input/output ports. SU-9070 PREAMP MANUAL
 

Hello man

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It currently "works" as in the preamp has two other outputs. The sub has the ability to use RCA not just coax as an input. The problem is, I turn the volume of the speakers down but the sub stays at the same volume, meaning all I hear is a ton of bass when the speakers are turned down.
 

makkem

Distinguished
Hi
The volume control on pre-amps is generally on the output so none of the other outputs will work in that respect.
The easiest way would be to use a splitter cable on either the left or right outputs,it should work on most things as the bass is generally center panned on recordings.
 

Hello man

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Ok. The matching amp that goes with the preamp is running off the "DC" output on the preamp. Next to the "DC" output is another output. Here is a pic


You can see the "EXT UNIT" output, which is what I currently have the sub running off of (the sub is unplugged in that pic). The amp is plugged into the "DC" output, and the purple interconnect goes from my MusicHall DAC to the preamp. Which output should I use for the sub? The one next to the DC output or the "EXT UNIT" output?
 

Hello man

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Haha this gear is old, but still worth a lot of cash (as much or more than its original purchase price). If the subwoofer is powered then it would go direct to the sub from "normal"?
 

Hello man

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It's a powered Polk PSW303 if I can remember. Ill give the "normal" a try with the preamp at a low volume to make sure it doesn't blow up :D That would be less than ideal.
 

Hello man

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Seems to work on the "normal", but its pretty quiet cause the speakers have to be up lout to get much out of the sub. Ill play around with it more and see what I can get out of it.
 

Hello man

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I think the "normal" output is just a volume regulated version of the "EXT UNIT" output. So when the preamp is turned down (I never nun it that high, my speakers are pretty loud) the sub is pretty quiet unless its volume is way up. SO I just put it back on the "EXT UNIT" and change the entire system volume from my laptop. Thanks for your help.
 

madmatt30

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That Polk should have speaker level inputs/outputs??
You should be using your left/right speaker outputs from you main amp to the sub speaker in ,then link your speakers to the speaker out on the sub.
That's the correct way to do things if you have no dedicated coax sub output on either amp.
 

madmatt30

Honorable
That Polk should have speaker level inputs/outputs??
You should be using your left/right speaker outputs from you main amp to the sub speaker in ,then link your speakers to the speaker out on the sub.
That's the correct way to do things if you have no dedicated coax sub output on either amp.
 

Hello man

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It has line level inputs. But it also has RCA interconnect type inputs. It works the way I have it right now.
 

Hello man

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This is true. I just leave my preamp/sub at one volume and turn down the input.
 
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