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Topic: Connect passive sub to Pre-out Sub in AMP (Read 4318 times) previous topic - next topic
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Connect passive sub to Pre-out Sub in AMP

This should be easy, but now that I am a senior I am having problems remembering some of the audio basics that were my forte.

So I have a second audio system in my bedroom in which I installed a Pioneer VSX-D511 receiver.  Quoted loudspeaker requirements are 8 to 16 Ohms. This is a typical low end 5.1 receiver.  Here are two facts that have bearing in this pair of questions:

1)   My surround speakers are 6-Ohms.  This is close enough to spec that there should not be any problems ????

2)   The sub that I have is a Sony passive sub rated at 3-ohms.  I cannot afford to replace it at this time on my meagre pension.  The Pioneer receiver has only a Preamplified Subwoofer output to go to a powered sub. Obviously a miss-match. 

My perceived work-around for question #2 to connect the Pioneer PreSubOut to a second amplifier's MONITOR-IN.  Then take the signal from MONITOR-IN to Speaker-terminal<right>, and from there to the Sub's inputs.  Should work, right ??

But I'd like to get confirmation from you the expert:

-  Is there a serious mismatch in expected Ohms to damage any of the components? 
-  Is there a potential problem connecting the Pioneer's PreSubOut to an AMP's TapeMoniorIn ?
-  To prevent damage to the secondary AMP, do the two front channel SpeakerOuts of that AMP need to be connected to a load?
- If so, how can the two loads be combined from 2nd Amp SpeakersOut into out the single SpeakerIn on the Sony sub ?

FYI the "slave" or second receiver here is a vintage Toshiba SA304 . . . an SQ Quad receiver.  One of the back channels has a fault, so Using it for this purpose would be a kind offering in its memory.

Any and all responses would be most welcomed.

Regards to all,
-=DrBinns=-

Re: Connect passive sub to Pre-out Sub in AMP

Reply #1 –
Quote
1)   My surround speakers are 6-Ohms.  This is close enough to spec that there should not be any problems ????
You should be OK, especially if you don't  "push" the amplifier too hard.   But, you are beyond the specs so you're on your own.   Most modern amps/receivers have some kind of thermal protection so they only temporarily shut down, but no guarantees...

Quote
2)   The sub that I have is a Sony passive sub rated at 3-ohms.
That's low too.  What's the impedance rating on the 2nd receiver? 

Quote
-  To prevent damage to the secondary AMP, do the two front channel SpeakerOuts of that AMP need to be connected to a load?
- If so, how can the two loads be combined from 2nd Amp SpeakersOut into out the single SpeakerIn on the Sony sub ?
It's OK to leave the unused outputs (and inputs) un-connected. 

Do NOT attempt to "combine" the outputs.

With nothing connected to the speaker outputs no current flows so it's actually easier on the amp than having a load.
  

Re: Connect passive sub to Pre-out Sub in AMP

Reply #2 –
Quote from: DVDdoug on
Quote
1)  My surround speakers are 6-Ohms.  This is close enough to spec that there should not be any problems ????
You should be OK, especially if you don't  "push" the amplifier too hard. 
As this is in my bedroom and my cat does not like loud music ;) together with the fact that the music itself is classical music, eg. Vaughan Williams, "The Lark Ascending")  I think I should be fine in that area then.
Quote
2)  The sub that I have is a Sony passive sub rated at 3-ohms.
Quote
That's low too.  What's the impedance rating on the 2nd receiver? 
Sorry, should have mentioned that . . . it is rated  4 to 16 OHMS.    Actually, I've never seen 3-ohms before and for Sony "home theater system" speakers, I am most surprised indeed.  I am thinking that the sub being low by 1 ohm and thus (3 to amp's min 4) 1/4 or 25% too low . . .  compared to the rear speakers being low by 2 ohms (6 to amp's min of 8 ) , again 1/4 or 25% too low . . . both scenarios are equal.  However, my policy has always been not to vary more than +/- 10% from spec, so maybe I should not really terrifically comfortable with this in the long term.  In other words, though I may run it as is for now, I should look for opportunities to replace these loudspeakers.  In any case, I will be sure not to be pushing that sub very much.
Quote
-  To prevent damage to the secondary AMP, do the two front channel SpeakerOuts of that AMP need to be connected to a load?
Quote
With nothing connected to the speaker outputs no current flows so it's actually easier on the amp than having a load.
 
Thank you for that. I have never been clear on that issue.

So thank you very much for the help DVDdoug.  I appreciate it very much.  All I will need really (for now) is a remote for the Pioneer VSX-D511 receiver.  Mine came without a remote.  Maybe someone here has one for sale ? 8)

BTW, do you agree with my 25% rationale ?  And do you agree that the pre-amplified SUB-Out on the first receiver  is best sent to the second amp's MONITOR-In ?  Or does it even matter ?

Thanks again . . .

Re: Connect passive sub to Pre-out Sub in AMP

Reply #3 –
Quote from: DrBinns on
This should be easy, but now that I am a senior I am having problems remembering some of the audio basics that were my forte.

So I have a second audio system in my bedroom in which I installed a Pioneer VSX-D511 receiver.  Quoted loudspeaker requirements are 8 to 16 Ohms. This is a typical low end 5.1 receiver.  Here are two facts that have bearing in this pair of questions:

1)   My surround speakers are 6-Ohms.  This is close enough to spec that there should not be any problems ????

2)   The sub that I have is a Sony passive sub rated at 3-ohms.  I cannot afford to replace it at this time on my meagre pension.  The Pioneer receiver has only a Preamplified Subwoofer output to go to a powered sub. Obviously a miss-match. 

My perceived work-around for question #2 to connect the Pioneer PreSubOut to a second amplifier's MONITOR-IN.  Then take the signal from MONITOR-IN to Speaker-terminal<right>, and from there to the Sub's inputs.  Should work, right ??

But I'd like to get confirmation from you the expert:

-  Is there a serious mismatch in expected Ohms to damage any of the components? 
-  Is there a potential problem connecting the Pioneer's PreSubOut to an AMP's TapeMoniorIn ?
-  To prevent damage to the secondary AMP, do the two front channel SpeakerOuts of that AMP need to be connected to a load?
- If so, how can the two loads be combined from 2nd Amp SpeakersOut into out the single SpeakerIn on the Sony sub ?

FYI the "slave" or second receiver here is a vintage Toshiba SA304 . . . an SQ Quad receiver.  One of the back channels has a fault, so Using it for this purpose would be a kind offering in its memory.

Any and all responses would be most welcomed.

Regards to all,
-=DrBinns=-


As long as you don't play this system very loud, no problems are to be expected. The 3 ohm subwoofer is a bit strange but people do this sort of thing for HTIB in order to maximize the power available to the (usually quite low efficiency) subwoofer.

I believe you said that this system will not be played really loud, and that cuts you quite a bit of slack.

To clarify, leaving some or all of the channels of a SS amp or receiver disconnected  should cause no problems. Its some old tube amps that had problems with this.

Seems like your ole' memory cells are still hitting on all cylinders.