Technics Su-x902 with a subwoofer

BrutalPizza

Active Member
Back with another question, similar to a question I had before.
I was given lots of advice from people, however after realising some things, it may not work, so I am going to make sure.

So i have a technics su-x902 amplifier.
It has A and B speaker outputs.

I want to use A with some cambridge audio sx80 speakers.
On the B channel I am planning to use a cambridge audio aero 9 (this sub does not have speaker level inputs, just line level and lfe)
Also note that this amp will only work with both A and B at the same time, if speakers are actually connected to both of those A and B channels. As it creates a circuit or something like that, the amplifier supports a minimum impedance of 8 ohms. The sx80s are 8 ohms 100w which is exactly what this amp outputs.

So, what I was originally planning on doing, was having a speaker to line level converter on the B channel for the aero 9 sub, but will that actually work with an amplifier like this? And will it create an impedance load?

The second thing I had in mind, would be to use one of the Rec Out tape deck/dat connectors, run that into an auxillary connector on my home theatre reciever, and then have the aero 9 connected to the lfe output on my home theatre reciever (in stereo mode with the speakers switched off).

So would my first plan with the line level converter actually work?
Or would my second option be the better choice?

As for my second option, I suppose I could actually just connecct the rec out connector straight into the subs line level connectors, however. I dont think it would be very loud, which is why I had the idea of using my home theatre reciever in mind.

-Thanks everyone
-Matt
 

BrutalPizza

Active Member
Option 1 won't work, as the speaker to line level adapter will be very high impedance.

Connect the speakers AND the converter to output A and this will work fine. This Speaker to RCA Converter / High to low Line Level Converter: Amazon.co.uk: Electronics is all you need.
The issue with that one is that it looks like another one I saw that didnt support the wattage that my amp outputted. I need to make sure that it supports 100 watts. Also, if they add a very high impedance, wouldnt that effect the A channel with the speakers on as well?
 

noiseboy72

Distinguished Member
No problems with either the wattage or impedance. All these things do is use basic, passive components to deliver a high impedance lower level version of the amplifier output. The boxes don't use any current, so the wattage is unimportant and a high impedance means that they won't affect the speakers, which have a low impedance. For impedance, read load - or how much stress the amplifier is put under. The lower the impedance, the higher the load. Therefore, a high impedance load won't affect either the amplifier or the speakers.

Your amp might be rated at 100w, but in reality you would never get close to this figure, as the dynamic nature of music would give a much lower average power of maybe 30w if you were running the system at ear bleeding levels.
 

BrutalPizza

Active Member
No problems with either the wattage or impedance. All these things do is use basic, passive components to deliver a high impedance lower level version of the amplifier output. The boxes don't use any current, so the wattage is unimportant and a high impedance means that they won't affect the speakers, which have a low impedance. For impedance, read load - or how much stress the amplifier is put under. The lower the impedance, the higher the load. Therefore, a high impedance load won't affect either the amplifier or the speakers.

Your amp might be rated at 100w, but in reality you would never get close to this figure, as the dynamic nature of music would give a much lower average power of maybe 30w if you were running the system at ear bleeding levels.
Could I still get a one like this though to be sure?
Russound ADP1.2 Speaker-Level to Line-Level Stereo Converter - CyberSelect
 

noiseboy72

Distinguished Member
Yep! That works out at just under £10 per resistor - which actually cost about 60p each, but it's your money...

The unit I linked to contains pretty much the same circuitry, but has variable resistors so that you can trim the output if required. This can be useful if you are overloading the input of the sub, but is not normally an issue.
 

BrutalPizza

Active Member
Yep! That works out at just under £10 per resistor - which actually cost about 60p each, but it's your money...

The unit I linked to contains pretty much the same circuitry, but has variable resistors so that you can trim the output if required. This can be useful if you are overloading the input of the sub, but is not normally an issue.
Ill probably get the 1st one you sent me then, are you sure the power handling will be fine? Because the amp I have also has super bass which is like their kinda of extra bass system, and im wondering if it will still take the power of that at loud levels.
 

noiseboy72

Distinguished Member
It will be fine. Turn the Super bass control to minimum and also switch off the Dynamic Sound setting, so you are sending a flat signal to the main speakers and then just adjust the sub to give the deep bass at a level that you want. This will give you the most natural sound and will optimize the power available from the amp.

Play with the filter control and also the phase switch on the sub, as you may find that you can make thinks sound tighter by flipping the phase. This can help with getting rid of the overlap peak between the sub and the mains. The filter will allow you to fill in what's missing from the mains and keep things sounding natural.
 

BrutalPizza

Active Member
It will be fine. Turn the Super bass control to minimum and also switch off the Dynamic Sound setting, so you are sending a flat signal to the main speakers and then just adjust the sub to give the deep bass at a level that you want. This will give you the most natural sound and will optimize the power available from the amp.

Play with the filter control and also the phase switch on the sub, as you may find that you can make thinks sound tighter by flipping the phase. This can help with getting rid of the overlap peak between the sub and the mains. The filter will allow you to fill in what's missing from the mains and keep things sounding natural.
Sorry, really hope you dont mind.

One last thing, if I turned the sub off and just wanted to listen to the main speakers, again would it hurt the line level converter to have the super bass on and the dynamic thing on?

And thaks for the advice, really appreciate it.
 

noiseboy72

Distinguished Member
Nope, it won't hurt it. It doesn't give you any extra power, it just increases the perceived bass using I think a sub harmonic synthesizer to create low frequency information that is not actually there on the recording. Loved by DJs and Reggae aficionados the world over :)
 

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