Using a powered woofer with a gainclone 3886 amp

nightanole · 15th January 2010, 01:52 AM

Im building a kit from chipamp.com right now. Also my 10 year old onkyo is dieing. The onkyo system is for my computer and consists of using optical out from my sound card to the receiver, and from there to a pair of nice bookshelf speakers. They are set to small via the receiver, and the lows are sent to the powered sub via sub out on the receiver. I cant seem to figure out a good way to use the sub if i replace the receiver with the gainclone and one of my usbdacs.

Should i just make a 6db passive line crossover inbetween the pot and the 3886. Just split it and have 100hz goto the sub and above goto the 3886 bookshelf speakers? aka alittle sub out on the amp? And for the simple math for the chipamp, the amp impedance should be about 23k if its a stock 3886 build right?

kgb_m3 · 15th January 2010, 06:04 AM

I'm in the same situation except I'll be using the 3886 to run bookshelf speakers and use my old Onkyo powered sub meanwhile I build my own sub/amp. I plan on splitting the line out signal from the sound card since this will be a 2.1 pc system and running one split to the lm3886 and the other directly into the powered sub. The sub has a an adjustable crossover built in, if yours has the same you can just set the low pass filter say at 80hz and your speaker crossovers along with the 3886 will take care of the rest. Can you be more specific about your sub and your preamp or whatever you're using to feed the signal to the amp/sub.

nightanole · 15th January 2010, 12:08 PM

Well like i said im still building the amp. My sound source i want to be a usbdac since i just have onboard sound and a decent sounding sound card seems to be more then the cost of the amp. I have no preamp if i just install a pot into the amp to make it integrated. I was planing on keeping everything in one case. So the box would just have usb in and speaker out. However i cant do sub out like that.

The powered sub is an older model from paradigm. I havent looked at the back of it in a while but it does have phase and freq adjust.

kgb_m3 · 15th January 2010, 05:17 PM

So what exactly is the usb dac using as an output? RCA, 3.5mm? I don't see why you can't just split the signal with a splitter jack/plug and run one split to the 3886 and the other directly into the subwoofer. The signal has the entire frequency range, the sub will take care of its dedicated low hz range and your speakers will pick up the rest. Can you post the model or picture of your usb dac?

nightanole · 15th January 2010, 05:43 PM

Ok the usb dac does not have volume control. Its outputs dont matter since i can solder anything i want on them(hell right now its just a board with nothing soldered to it).

Problems taping at the dac, no volume control.

problems splitting after the pot, bookshelfs have full range signal. So ya i can just run full range to the sub and use the subs crossover, but i still have to filter the lows out of the signal to the 3886, which is my main question. How is the best way to do that?

tomchr · 15th January 2010, 05:55 PM

If you want a reasonably flat frequency response, you will need filtering. Sometimes, a powered sub will have the filter built-in and it will provide a filtered output that you can run to your power amp for the bookshelf speakers. You will also need some level/volume control so you can balance the sub and the bookshelf speakers in terms of volume level.

An active filter is a slick way of doing it. Look at the Linkwitz-Riley filters, for example. If you don't want to build your own, you can also look at something like the Ashly XR1001. They can be had for $100-ish on [THAT AUCTION SITE].

If you don't care about HiFi but just want noise from the computer to come through the speakers, a couple of RC's is probably fine. Or as others suggest, just hook the full-range signal to both the sub and the bookshelf speakers and tweak it until you're happy. It'll play the pathetic Windows sounds just fine...

~Tom

kgb_m3 · 15th January 2010, 06:23 PM

Active filter is definitely the best way to go, maybe overkill for what OP's trying to accomplish. All depends on how much time you want to put into this.

nightanole · 15th January 2010, 06:25 PM

Well i want it to sound good (its why im using a usb dac and not onboard sound). If i could find a diy pcb that i could just solder the values on that i need for the active crossover id do that. However i havent found one yet. This is why i was thinking of just using a simple rc filter. I know it will drop the signal, but i have a very high voltage dac at 2vrms. Are you saying a rc 6-12db passive filter will sound worse then a active crossover that cost more then the amp itself?

If you have a spot were i can buy an active crossover diy pcb please please tell me.

kgb_m3 · 06:33 PM

This might work Active Filter Circuit - Active Filter Circuits - Electronic Circuits - Hobby Projects

You can make your own PCB for it, of course if you're up for it.

15th January 2010, 01:52 AM	#1
nightanole diyAudio Member Join Date: Feb 2009	Using a powered woofer with a gainclone 3886 amp Im building a kit from chipamp.com right now. Also my 10 year old onkyo is dieing. The onkyo system is for my computer and consists of using optical out from my sound card to the receiver, and from there to a pair of nice bookshelf speakers. They are set to small via the receiver, and the lows are sent to the powered sub via sub out on the receiver. I cant seem to figure out a good way to use the sub if i replace the receiver with the gainclone and one of my usbdacs. Should i just make a 6db passive line crossover inbetween the pot and the 3886. Just split it and have 100hz goto the sub and above goto the 3886 bookshelf speakers? aka alittle sub out on the amp? And for the simple math for the chipamp, the amp impedance should be about 23k if its a stock 3886 build right?

15th January 2010, 06:30 PM	#9
kgb_m3 diyAudio Member Join Date: Dec 2009	This might work Active Filter Circuit - Active Filter Circuits - Electronic Circuits - Hobby Projects You can make your own PCB for it, of course if you're up for it. Last edited by kgb_m3; 15th January 2010 at 06:33 PM.

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15th January 2010, 06:04 AM	#2
kgb_m3 diyAudio Member Join Date: Dec 2009	I'm in the same situation except I'll be using the 3886 to run bookshelf speakers and use my old Onkyo powered sub meanwhile I build my own sub/amp. I plan on splitting the line out signal from the sound card since this will be a 2.1 pc system and running one split to the lm3886 and the other directly into the powered sub. The sub has a an adjustable crossover built in, if yours has the same you can just set the low pass filter say at 80hz and your speaker crossovers along with the 3886 will take care of the rest. Can you be more specific about your sub and your preamp or whatever you're using to feed the signal to the amp/sub.

15th January 2010, 12:08 PM	#3
nightanole diyAudio Member Join Date: Feb 2009	Well like i said im still building the amp. My sound source i want to be a usbdac since i just have onboard sound and a decent sounding sound card seems to be more then the cost of the amp. I have no preamp if i just install a pot into the amp to make it integrated. I was planing on keeping everything in one case. So the box would just have usb in and speaker out. However i cant do sub out like that. The powered sub is an older model from paradigm. I havent looked at the back of it in a while but it does have phase and freq adjust.

15th January 2010, 05:17 PM	#4
kgb_m3 diyAudio Member Join Date: Dec 2009	So what exactly is the usb dac using as an output? RCA, 3.5mm? I don't see why you can't just split the signal with a splitter jack/plug and run one split to the 3886 and the other directly into the subwoofer. The signal has the entire frequency range, the sub will take care of its dedicated low hz range and your speakers will pick up the rest. Can you post the model or picture of your usb dac?

15th January 2010, 05:43 PM	#5
nightanole diyAudio Member Join Date: Feb 2009	Ok the usb dac does not have volume control. Its outputs dont matter since i can solder anything i want on them(hell right now its just a board with nothing soldered to it). Problems taping at the dac, no volume control. problems splitting after the pot, bookshelfs have full range signal. So ya i can just run full range to the sub and use the subs crossover, but i still have to filter the lows out of the signal to the 3886, which is my main question. How is the best way to do that?

15th January 2010, 05:55 PM	#6
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	If you want a reasonably flat frequency response, you will need filtering. Sometimes, a powered sub will have the filter built-in and it will provide a filtered output that you can run to your power amp for the bookshelf speakers. You will also need some level/volume control so you can balance the sub and the bookshelf speakers in terms of volume level. An active filter is a slick way of doing it. Look at the Linkwitz-Riley filters, for example. If you don't want to build your own, you can also look at something like the Ashly XR1001. They can be had for $100-ish on [THAT AUCTION SITE]. If you don't care about HiFi but just want noise from the computer to come through the speakers, a couple of RC's is probably fine. Or as others suggest, just hook the full-range signal to both the sub and the bookshelf speakers and tweak it until you're happy. It'll play the pathetic Windows sounds just fine... ~Tom

15th January 2010, 06:23 PM	#7
kgb_m3 diyAudio Member Join Date: Dec 2009	Active filter is definitely the best way to go, maybe overkill for what OP's trying to accomplish. All depends on how much time you want to put into this.

15th January 2010, 06:25 PM	#8
nightanole diyAudio Member Join Date: Feb 2009	Well i want it to sound good (its why im using a usb dac and not onboard sound). If i could find a diy pcb that i could just solder the values on that i need for the active crossover id do that. However i havent found one yet. This is why i was thinking of just using a simple rc filter. I know it will drop the signal, but i have a very high voltage dac at 2vrms. Are you saying a rc 6-12db passive filter will sound worse then a active crossover that cost more then the amp itself? If you have a spot were i can buy an active crossover diy pcb please please tell me.

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