Would like to add subwoofer out to Gainclone

My latest LM3886 Chipamp build took the place of a Manley Stingray in my main setup, the sound is spectacular. I'd like to add a subwoofer output (can't run from the binding posts as the sub is small and doesn't have speaker level inputs). I tried running an output after the volume control (before the signal is amplified) to the sub but that didn't work.

It's looking like this may be an option:
http://www.sunsky-online.com/product/default!view.do?contact=&subject.id=315226

and this for power: Avel Y236103 30VA 15V+15V Toroidal Transformer

and throw both in a box, then send the volume controlled signal to that.

Any thoughts/recommendations? TIA.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I don't think that processor kit is anything more than a level control with an adjustable filter to set the upper roll-off frequency. You may need a bit more than that, depending on what your subwoofer already does, like is it a self-powered subwoofer? Does it have auto power-up etc? What is its rated output power?

If nothing happened when you connected the audio from the volume control to the subwoofer input, that kit won't do any more - you may need to use a another power amplifier, like a plate amp, that includes all the necessary controls. It does depend on how big your system is too. Chipamps can produce a lot of power and require lots more bass power to balance that.
Dayton Audio Engineered Subwoofer Plate Amplifiers
 
Thanks for the follow up Ian, plugging the sub in to the RCA outputs (which are wires after the pot and before the amp section) caused the music on the main speakers to get quieter and more distorted, I guess the amplifier in the sub could have a virtual ground that is causing the issue, but I'm no EE. I was hoping to isolate the signal before it is sent to the subwoofer to see if that eliminates the issue.

The sub is a 1000W Energy model, 8" driver and dual radiators, I believe it has auto-power up.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
OK, that seems like a powered sub. if it has a mains power cord, switch for phase, crossover, volume controls etc. on the rear or via a remote controller. 1 kilowatt through an 8" driver though? That must be automotive watts. The only Energy sub. I can see is marketed by Klipsch and that's 100W - that's believable at least.

Anyways, a 10k resistor in series with each + signal lead to the sub. out sockets, takes care of the necessary isolation. That keeps your normal L & R speakers fed with signal, as you'd expect. The input impedance of the RCA sockets on the sub. should be 10 - 50k, and easy to drive. There could be some problem there but start out with just the resistors fitted. Standard 1/4W metal film resistor types connected right at the tap-off point will be fine. It may be that a simple output buffer (like a preamp with no gain) is needed but let's see what happens first.

The sub does work from an RCA lead input in another system, I guess?
 
Thanks Ian, I really appreciate your time and your assistance. It's always hard when you ask a legitimate question and get no responses, so you're my saving grace. I try to do the same thing on HeadFi, fortunately those DIY questions are a lot easier! ;)

http://www.amazon.com/Energy-ESW-M8-NA-Discontinued-Manufacturer/dp/B004TA8YNW

So yes, it's a powered 8", 1,200W peak, 300W RMS, so inflated marketing watts ;) It's very compact, so it uses the extra wattage to account for that. It was working perfectly with the Manley. I also have a 6.5" version that I use with an original circuit Dynaco PAS and ST-35 in my workshop, so I know it can get along with other DIY gear. I've got plenty of 10K resistors sitting around, so I'll give it a shot and report back.

Thanks again Ian. Again... I really appreciate your help.