Adding a sub output to a chip amp

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fingersoccer

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Joined 2010
#1
I'm building a chip amp and I'd like to add a mono line-level output to feed an active subwoofer. I'm not sure how to do that, so a couple questions:

1) What's the best way to split the preamp's stereo signal between the amp input and subwoofer output?

2) How do I sum the stereo preamp signal to feed a single RCA connector for the subwoofer out?

Thanks for any words of wisdom you can impart.
 
#3
I dont think it would work out very well... It would ruin the stereo thingy...

If I built a subwoofer amp, id use dual opamp and parallel the outputs...
But there would be 1 killer... The resistor connected between in and output would ruin everything.
 
#6
Minion said:
Maybe a circuit like this would be suitable :
Click to expand...
Doesn't this circuit create the potential for crosstalk into the separate L & R signals? If so, preceding this circuit with a unity gain buffer for each channel should provide isolation.
It might be interesting to know if there are positives and negatives between sum>filter and filter>sum, or if it makes no difference.
 
#7
fingersoccer said:
I'm building a chip amp and I'd like to add a mono line-level output to feed an active subwoofer. ........
Click to expand...


Here are some very low cost, tested and ready to build circuits and they provide very effective solution.

There are several options.
Kindly check out the following links:

1. Construction of a low pass filter: http://construyasuvideorockola.com/proy_filtrobass.php

PDF for toner transfer to make your own home made PCB:
http://construyasuvideorockola.com/downloads/pre_subw_car.pdf
The pdf file contains documentation on how to sum up your stereo channels. But I would say please follow Sir AndrewT's advice while summing your signal.

You can build a simple regulated PSU for the LOW PASS Filter using the link
http://construyasuvideorockola.com/proyecto_fuente_simple_regulada.php

You can also make an active summing amplifier from the following link:
http://construyasuvideorockola.com/proy_sumador.php if you need more gain.

OR

You can try this sub woofer circuit designed by respected Mr Mile
http://www.diyaudio.com/forums/analog-line-level/167363-mic-line-eq-preamps-11.html#post2223269

OR

You can give this link a further reading to understand more. My subs are driven with this circuit and I am more than happy with their performance.
This has independent subs per channel, no summing/mixing done.
Silicon Chip Online - Active 3-Way Crossover for Loud Speaker Systems


Hope this helps.
 
Last edited:
#8
Excellent responses, one and all, I thank you with handshakes.

For the summing circuit posted above, are "First Input" and "Second Input" just the L/R signals from the preamp? In other words, should I feed the summing circuit like the mockup below?

KBu1MMp.png
 
#9
fingersoccer said:
Excellent responses, one and all, I thank you with handshakes.

For the summing circuit posted above, are "First Input" and "Second Input" just the L/R signals from the preamp? In other words, should I feed the summing circuit like the mockup below?

KBu1MMp.png
Click to expand...
You are right.
If the summing section is done correctly , the sub should rock.
I summed Left and right signals into a mono signal to feed a giant LED spectrum analyser, and no loss in the stereo image and I have not used a signal distribution amplifier .
http://www.diyaudio.com/forums/chip...battery-powered-mini-boombox.html#post3639321
 
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