Sub woofer amp

[Sam T]

Sorry if I have double posted. It did not seem to submit the first time.

Yesterday we had to buy a new main amp for the home theater since the old one died. It has two sub woofer amp outputs. The amp that powers the sub woofer was built by my dad in the 1980's. On the previous main amp we ran the sub woofer amp out of the front speaker connections but on the new one we made a lead and hooked it into the sub woofer amp output. After doing that, the sub woofer amp had to be set to full and the setting on the main amp had to be turned up in order for the sub woofer to work, but it still was not very good. For the moment it is hooked into the front speakers, but we would like it to work in the sub woofer amp output so we can stop sending the bass to the front speakers.
Would the overall setup sound better by doing this?
I was thinking about modifying the old sub woofer amp, but decided there would be better diy amp around now. I am interested in electronics and dad is an electrician so i can get help in building an amp. I think the old one is a modified playmaster 200W.
Thanks for any help!
Links are great.

[jaycee]

If you previously had the sub connected to speaker-level outputs, there is probably some kind of attenuation circuit in the subwoofer to step that down to line level signals. This is not required if your new reciever already has a line level sub out.

The Playmaster amp is probably still up to the task, and may only need minor work such as new power supply capacitors.

[Sam T]

Originally posted by jaycee
If you previously had the sub connected to speaker-level outputs, there is probably some kind of attenuation circuit in the subwoofer to step that down to line level signals. This is not required if your new reciever already has a line level sub out.

The Playmaster amp is probably still up to the task, and may only need minor work such as new power supply capacitors.

I will work out which model it is and try to find a wiring diagram for it.

Also i would still be interested in building an amp. Can someone recommend one?

[RocketScientist]

Originally posted by Sam T

Also i would still be interested in building an amp. Can someone recommend one?

There's nothing particularly magic about subwoofer amps. A lot of things that make a difference for a full range amp don't matter nearly as much for a subwoofer amp. So they make good DIY projects as they're more forgiving in some ways.

It's also a good application for Class-D. Nearly all the well regarded commercial subs these days are Class-D which allows them to pack a lot more power without needing huge heatsinks or special ventilation. And Class B designs get both expensive and tricky when you exceed around 300 or 400 watts while Class D can scale up to 1000 watts without any huge issues. Class D also helps keep your electric bill lower using almost no power when idle or at low signal levels. So the Class D forum here would be one good place to start.

But, unless your heart is set on DIY, I'd suggest also looking at some of the commercial subwoofer amps from Parts Express and even on eBay. It's hard to beat China Inc for dollars per watt. And, I'm sure some here (especially those who have put a lot of time and money into their own DIY sub amps) will disagree with me, but I doubt you would notice much difference between most DIY designs and a cheaper commercial sub amp. Some of the best sounding (and reviewed) subs on the planet use relatively inexpensive Class D amps.

What does make a big difference in sub amps are things like variable phase, a good parametric EQ, well designed crossover, etc. And you can easily get all those things in a commercial design but they add complexity to a DIY project.

Others I know use cheap pro amps as subwoofer amps. A good example would be the Behringer A500 for under $200 USD which, when bridged to mono, is rated for around 500 watts and has the advantage of being fanless (unlike many pro amps).

The choice depends on how much power you're looking for, how much money you want to spend, what sort of driver your subwoofer has,how much you want to go DIY, etc. But, if you're not experienced in DIY amp projects, the costs can add up faster than you might think--especially if something goes wrong and you smoke some expensive parts or amp modules.

[Sam T]

The current sub woofer amp is a 100W 82pa7 published in Electronics Australia. I will look for a wiring diagram.

With the other diy amps, would someone please post a price range and possibly a link to a project .

Thanks for all the help!!!!

[RocketScientist]

I'd use something like this (300W - 500W Class-D):

http://connexelectronic.com/product_...7kengdglhsipv6