Quickie + SEX + Sub?

[jake111]

I'm planning on feeding a plate amp sub by using RCA splitters from the Quickie to the sub and SEX. Will this degrade the SQ feeding the SEX? In open air testing of the of the sub speaker it it does lower the volume control of the Quickie a little. My plate amp only has low level inputs. Is there a better way to do this?
Much thanks, Jess

 

[Paul Joppa]

As long as the cables are not too long, there should be no problem.

The reduced volume is probably due to a low input impedance of the plate amp. You should find it in the specs, or possibly online. My guess is 10K ohms.  :^)  As long as it's 10K or more, it should have little effect on the sound of a stock Quickie. But between 10K and 100K, it will limit the potential of the PJCCS.

 

[jake111]

Cool, it's 12K ohm.
Thanks Paul

 

[jake111]

Hey Paul. The Quickie has the PJCCS and maybe I dont want to mess up it's performance. So is this the right circuit to use if I want to pad down the speaker output on the SEX to drive the plate amp?

 

[Paul Joppa]

That will certainly work.

The SEX amp maximum output is only 4vRMS (at 8 ohms), so you may not need to attenuate at all.

 

[jake111]

Been awhile on this one. The plate amp volume turned out to sensitive so I finally built this attenuation circuit but wanted to test it before I try it out. What should the resistance readings be? I have no idea how to figure this out. Thanks

 

[jake111]

It worked! Now the gain knob goes half way as apposed to a fraction. How does having a plate amp connected like this affect output impedance on the SEX? Should I adjust the output impedance to account for an increase? It's set at 4ohm same as the main speakers. Is there a rule of thumb for the impedance switch? Should it be set lower, the same, or higher than the impedance of the speakers? What's the optimum? Sorry for the all the newbie questions.
Jess

 

[Paul Birkeland]

An 11K load in parallel with a 4 Ohm load is a 3.9985459832788077 Ohm load.  Considering that your speaker impedance probably varies between 2 Ohms and 50 Ohms, the 11K load in parallel is of no concern.  (Just don't set the impedance switch kit to balanced when you're running your plate amp in this fashion)

-PB

 

[jake111]

Oops, it's been set to balanced. I'll change that, but whats the harm?
Is there an optimum for the 4ohm load. I know on my 8ohm HT amp, it shuts down driving 6ohm speakers. So is it that you want the amp be set to drive an equal or higher ohm load so it wont overheat?
Thanks

 

[Paul Birkeland]

Oops, it's been set to balanced. I'll change that, but whats the harm?

You have the two speaker black posts connected together at the sub amp, which disallows a balanced output.

Is there an optimum for the 4ohm load. I know on my 8ohm HT amp, it shuts down driving 6ohm speakers. So is it that you want the amp be set to drive an equal or higher ohm load so it wont overheat?

You could hook a 1 Ohm speaker up on the 8 Ohm tap and not damage the amplifier.  The amp will distort pretty badly from the mismatch, and be fairly un-listenable setup in that manner.  The optimum load on the 4 Ohm tap is a speaker that is nominally 4 Ohms without dips going much under 4 Ohms.  Your HT amp will shut down because a lower impedance load will demand more currnent than the amplifier can deliver.

 

[jake111]

Thanks for the explanation.