How do I create a sub-out or connect a sub-woofer on a simple 2 channel amplifier?

[bp238]

The subject is a Pyle Pro PCA-1 mini amplifier. I want to drive 2 satellite speakers with this amp and hook up a powered sub-woofer. The problem is the Pro PCA-1 has no sub-out and only one set of speaker outputs. BTW, the sub-woofer has only a low level input. Ideally I would like to install a sub-out jack on the amp and hardwire it into the circuitry. I don't mind pulling off the cover and doing some soldering to get the job done. Of course if anyone knows of a similar $30 amp with the same footprint that has a sub-out, then that would be the best answer to this problem..

 

[JerryLove]

The short answer is "you don't" unless you are running a pre-amp (which seems unlikely: but perhaps)

I'm not aware of a speaker-level crossover that wouldn't cost more than just getting an AVR.

You can't just add a crossover inside that amp (and again: cost prohibitive).

The one exception would be if you are using a pre-amp (a source with a volume control). In that case, you could use a low-pass crossover (like a Behringer Super-X) in between the source and amp. You'll have to level-match and then use only the source's volume control.

This will cost more than replacing the amp with one that has a sub-out.

Maybe someone else will have a better idea: but I don't think you've got an option with that amp.

 

[markw]

You can't get there from here.

Simply put, you need a subwoofer with a right and left speaker level inputs. Hopefully, speaker level output as well.

 

[bp238]

Thanks for the reply Jerry. I didn't really want to make it more complicated by adding a pre-amp and I am assuming going to an amp with a sub-out will mean going to a "full sized" amplifier. My goal is to keep this simple and portable. I want to actually mount the Pyle amp onto the sub's case which I have already attached a carry handle to the top of and hang the satellite speakers on the side of for transport. I am using this setup for outdoor movies on a projection screen. I am really tired of lugging an amplifier out into the wilderness in my setup process...along with everything else. This project is all about downsizing.

 

[bp238]

Thank Mark but I really want to try and do this with the equipment I already have if at all possible. The sub I have has it's limitations I know but the goal in this thread is to make this work with this equipment...actually the alternate amp with the sub out in the same price point and footprint is still a possibility albeit a remote one at best.

 

[bp238]

Is it possible to split the low-level input to the amp from the source then merge left and right and then send it to the subs low level input? What would happen if I did that?

 

[JerryLove]

Is it possible to split the low-level input to the amp from the source then merge left and right and then send it to the subs low level input? What would happen if I did that?

Yes. You use a crossover to separate the LF and HF portions of the signals and then merge the LF. You would have exactly what you are looking for.

There are numerous options and numerous problems.

Let's say you split before coming into the Pyle at all (something I mentioned previously). Then level matching the speakers and sub is your main problem. If you change the gain control on either without the other you'll loose level matching. It can be done if all volume control is from the source.

There are companies like minidsp that make active crossovers for this.

You could try to perform the crossover after the gain control and before the amp. This would mean opening up the box, severing the connections between the gain and amp, splicing in a crossover, and then running the LF out back out of the box.

The problem is going to be the high-integration level in a small amp like that. If we were discussing a full-sized AVR, where the pre and amp are a bit more discreet, I'd feel more confident that there would be an easily identificable bridge to step in the middle of.

Of course your last option is performing the crossover at the post-amplification phase. The problem there is that your subwoofer's amp does not support speaker-level inputs. You could replace the plate amp with one which does.

 

[bp238]

Thanks Jerry. The sub does have a level/volume control so I can level match with that. Let's say I do this without a crossover...as I currently do with the big amp/receiver I lug around. This old amp does not have a sub-out so I have been using the headphone jack to get signal to the sub. It works fine.

So if I simply use RCA jack splitters and combiners with barrel fittings to hook things together, will it work?

The only thing I worry about with splitting that low level signal from the dvd player is the voltage in the low level signal. Will the sub and the amp each require so much voltage that there won't be enough to drive them both? This might require a trial and error answer..

 

[mattsk8]

If you build a man a fire, he'll be warm for a day. If you set him on fire, he'll be warm for the rest of his life.

Nothing to do w/ this post, but man your quote is flipping hilarious !!

 

[JerryLove]

So if I simply use RCA jack splitters and combiners with barrel fittings to hook things together, will it work?

Yes. if you set the filter on the sub (assuming it has one) where the mechanical roll-off kicks in on the bookshelves, and if you avoid phase cancellation problems, you may end up with workable sound. If your sub has the option: it may be tempting to bypass the sub filter. Resist this urge as it will create significant cone breakup and awful sound.

Again, you will need to control volume from the source once you've matched the speakers and sub.

Give it a shot. It risks nothing but some time.

The only thing I worry about with splitting that low level signal from the dvd player is the voltage in the low level signal. Will the sub and the amp each require so much voltage that there won't be enough to drive them both? This might require a trial and error answer..

I believe loss is -3db of gain. It should be fine.

 

[TLS Guy]

Your problem is your amp is stereo. You need to combine the left and right channels before the power amp stage. You can not combine them or everything will be mono.

So you need to build a two channel buffer amp.

The only way you can do this is to feed the signal from the grounds and cursors of the volume control.

Now you need a dual channel opamp chip. Send the left and right channels to the opamp input. Design the opamp for unity gain.

Then combine the outputs of the opamp and send it to your sub.

There is absolutely no other way of doing this.

There likely will be a low level voltage in that map that can power the opamp chip.

 

[JerryLove]

Unless his sub has L and R line-level inputs... but good point

 

[bp238]

OK tried that and the signal from low level inputs is not working on the sub-woofer input. Well, I say it's not working because although it's audible its not getting enough signal to make the sub create proper levels of sound. Evidently that sub-woofer input needs a higher db input than typical low level inputs produce..which makes sense if you think about it. On my home entertainment system, the sub-out has levels I can roll through making the sound level higher or lower through the sub without touching the volume control on the sub itself.

So I ran the sub-in directly off of one side of the high level outputs on the amp and of course it worked but I know I am creating an imbalance that will probably blow the output on the amp eventually. Or will it? I tried to check to what kind of resistance that sub-woofer input had and it shows like an open circuit. So if it acts like an open circuit, how can it create an imbalance? I would love it if someone knew what kind of draw that sub-in puts on a output from an amp, if any. I guess I could just run it like that and see if it blows..I'd only be out 30 bucks. That would suck if it happened in the middle of a movie though

 

[bp238]

thanks tls guy will these work?

 

[TLS Guy]

thanks tls guy will these work?

Yes that will work if you design the correct circuit.

If you use the high level (speaker) outputs, you must only use the left or right output, not both, or you will blow your amp. You can not connect amp outputs together.

 

[JerryLove]

OK tried that and the signal from low level inputs is not working on the sub-woofer input. Well, I say it's not working because although it's audible its not getting enough signal to make the sub create proper levels of sound. Evidently that sub-woofer input needs a higher db input than typical low level inputs produce..which makes sense if you think about it. On my home entertainment system, the sub-out has levels I can roll through making the sound level higher or lower through the sub without touching the volume control on the sub itself.

So your sub doesn't have a gain control?

 

[bp238]

So your sub doesn't have a gain control?

yes it has a gain/volume control on the front but when I tried to run low level into the sub-in it had very low sound when turned all the way up. when I hooked it to the high level outputs of the amp it cranked like crazy..had to turn it way down.

 

[bp238]

Yes that will work if you design the correct circuit.

If you use the high level (speaker) outputs, you must only use the left or right output, not both, or you will blow your amp. You can not connect amp outputs together.

TLS guy. Are you saying stealing signal from one high level output to power the sub will work without blowing the amp? If so, I'm done here and that was easy. Just want to clarify what you meant by "Yes that will work.."

 

[TLS Guy]

TLS guy. Are you saying stealing signal from one high level output to power the sub will work without blowing the amp? If so, I'm done here and that was easy. Just want to clarify what you meant by "Yes that will work.."

Yes that buffer amp will work. Since the signal from your preamp stage is low you gain design the buffer amps to have gain and then you won't need to use the speaker outputs.

 

[TLS Guy]

TLS guy. Are you saying stealing signal from one high level output to power the sub will work without blowing the amp? If so, I'm done here and that was easy. Just want to clarify what you meant by "Yes that will work.."

You can't connect the amp outputs together so you have to use just one.