[charmerci]

How does one hook up a sub when there are no speaker inputs on the sub? My pre-amp only has one set of pre-outs which go to my amp.

[low.pfile]

if your preamp has Tape Out RCAs that should work.

[charmerci]

if your preamp has Tape Out RCAs that should work.

Really? Cool, it does. Thanks!

[srb]

if your preamp has Tape Out RCAs that should work.

Tape out jacks are generally fixed line-level outputs that are not affected by the volume control.  To drive a sub, you need volume-controlled variable outputs or else you will have to manually change the input level control on the sub each and every time you change the volume on the preamp.

You may be able to use a Y-connector off the preamp outputs, but since this can affect the amplifier input impedance that the preamp sees, the results may not be totally predictable or desireable.

Steve

[charmerci]

if your preamp has Tape Out RCAs that should work.

No, it doesn't.

Tape out jacks are generally fixed line-level outputs that are not affected by the volume control.  To drive a sub, you need volume-controlled variable outputs or else you will have to manually change the input level control on the sub each and every time you change the volume on the preamp.

You may be able to use a Y-connector off the preamp outputs, but since this can affect the amplifier input impedance that the preamp sees, the results may not be totally predictable or desireable.

Steve

    Errr.
Note - manufacturers. Since subs have become immensely popular, all pre-amps should have two pre-outs as standard.

[charmerci]

I was hoping not to have to spend any more or much more money but I guess this will work?
http://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4

[JLM]

I was hoping not to have to spend any more or much more money but I guess this will work?
http://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4

Looks like it would work, but why go that route when a RCA "Y" connector (splitter/stacker) of some sort (as Steve indicated) would is simpler/cheaper?  Like these:

http://www.monoprice.com/Product?c_id=104&cp_id=10429&cs_id=1042904&p_id=7186&seq=1&format=2

http://www.audioadvisor.com/AudioQuest-Hard-Y-Adapter-1-Male-to-2-Female-RCAs/productinfo/AQM22FHRD/#.U2NvUF64lHg

[orientalexpress]

Looks like it would work, but why go that route when a RCA "Y" connector (splitter/stacker) of some sort (as Steve indicated) would is simpler/cheaper?  Like these:

http://www.monoprice.com/Product?c_id=104&cp_id=10429&cs_id=1042904&p_id=7186&seq=1&format=2

http://www.audioadvisor.com/AudioQuest-Hard-Y-Adapter-1-Male-to-2-Female-RCAs/productinfo/AQM22FHRD/#.U2NvUF64lHg

they're don't work ,sound like crap.i have the same problem but i have speaker input on my sub.

[JLM]

Don't understand why a simple "Y" or stacker connector plugged into the pre-amp outputs wouldn't/shouldn't work.  Have used similar and not noticed any issues.

[charmerci]

I guess I'll write the manufacturers of my equipment and see what they say.

[JoshK]

Tape out jacks are generally fixed line-level outputs that are not affected by the volume control.  To drive a sub, you need volume-controlled variable outputs or else you will have to manually change the input level control on the sub each and every time you change the volume on the preamp.

You may be able to use a Y-connector off the preamp outputs, but since this can affect the amplifier input impedance that the preamp sees, the results may not be totally predictable or desireable.

Steve

+1   ^^ he just gave you the right answer.

[JoshK]

Don't understand why a simple "Y" or stacker connector wouldn't/shouldn't work.  Have used similar and not noticed any issues.

They work fine provided the output impedance of your preamp is much lower than the parrallel impedance of your sub input and amp input.   Amp inputs are typically high enough, but often sub inputs are quite low putting a low of burden on the preamp if it doesn't have a super low output Z.  Tube preamps are typically most taxed, SS preamps should do just fine.

[charmerci]

They work fine provided the output impedance of your preamp is much lower than the parrallel impedance of your sub input and amp input.   Amp inputs are typically high enough, but often sub inputs are quite low putting a low of burden on the preamp if it doesn't have a super low output Z.  Tube preamps are typically most taxed, SS preamps should do just fine.

The output impedance of my pre-amp is 70 Ohms. (I don't think anyone publishes input impedances.  )

[Chromisdesigns]

The output impedance of my pre-amp is 70 Ohms. (I don't think anyone publishes input impedances.  )

Input impedance of an amp **can** be calculated from measurements you can make: (http://www.sengpielaudio.com/calculator-InputOutputImpedance.htm)

But since stacker connectors  or hard-y's are relatively cheap, why not just try it and see if it affects the sound you hear?  My rig has a Parasound PLD-2000 preamp feeding a modded Hafler DH220 and Energy EPS 150 sub via stackers on the preamp output, and I can hear no difference with the sub in/out of the circuit (sub gain turned all the way down).  YMMV, of course -- but the experiment should be pretty inexpensive to do.


--Edited-- excuse the senior moment above -- I mis-remembered how it was hooked up.  Sub is on the second set of outputs, I was "remembering" the stackers on the "direct" preamp INPUT I use to drive my headphone amp so the sub doesn't come on when I am listening to cans with the preamp/main amp off.

[charmerci]

Well Y not?    I'll give the Y-connectors a try.

[charmerci]

I'm using one Y connector - right pre-out from pre-amp.


Should I be using two? (That is, also one from the left pre-out to the sub.) Will only using one and this imbalance cause any harm?

[srb]

First, with the output that has the Y-adapter you can compare the sound through the one speaker with the sub disconnected versus connected with the sub input level set to "0" and see if you can tell on this system if the combined imput impedance has any effect on either the frequency response or the output level.

I don't think there is any harm in deriving bass from just one channel, but more often than not low bass content is not identical in both stereo channels, so you may not be getting all of the bass content that you should.  Many subwoofers have Left and Right channel inputs to re-combine the bass for a single mono sub.

Steve

[charmerci]

Thanks. I'll go the safe route and get another one.

[barrows]

If we are talking about a high end stereo system here (not home theatre) I would highly recommend another method.  I have integrated quite a few subs, and I always prefer driving the sub from the amplifier outputs.  This method always seems to result in better integration of the sub and the main speakers.
It is too bad all subs do not come with high level inputs for this purpose, but, all is not lost. 
Most subs can be connected directly to the speaker outputs of an amp with a little intervening circuitry.  I would recommend contacting the manufacturer of your sub, and asking them if they can recommend a way to hook the sub up to the amplifier output.  Be prepared with all the specs of your amplifier when you contact the sub manufacturer.   

[James Romeyn]

First, with the output that has the Y-adapter you can compare the sound through the one speaker with the sub disconnected versus connected with the sub input level set to "0" and see if you can tell on this system if the combined imput impedance has any effect on either the frequency response or the output level...
Steve

Best advice above IMHO.  If the system is of certain quality, connecting the sub amp will most likely diminish main speaker performance.  If so, power the sub amp from the Main Speaker binding posts with Jack Elliano's so-called "bridging circuit" converting speaker level to line level: 9k series resistor on the source side, 1k parallel resistor on the load side. 

Install both resistors in the IC plug at the sub amp, or directly to the input jack of the sub amp (1/8W seems to work fine, use 1/4W if you purchase resistors).  Use practically whatever wire you want for the IC, as low as 20AWG will work.  If wire is unshielded pair I'd twist them together.  Long runs won't diminish performance.