Amplifier project

[Jan Mattfolk]

I am planning to build an active subwoofer to go with my TV set. Since i don´t have any external speakers at the moment i also need some amplification for two towers with mids and tweeters. My intentions are to build following:
- An amplifier for my subwoofer (8 ohm) including lpf
- Another 2 channel amp for my towers.
- Filters

My first idea was to integrate everything into the subwoofer (like 2.1 system), but i am realizing it isn´t the right way to go. I would later on like to use the sub in a 5.1 or 7.1 system, so it should only have one channel and line in. As i first intended it would have 2 channels, which would work for now but isn´t very flexible.

I was looking at the velleman k8060 as subwoofer amp, but isnt quite sure. I have also looked a bit at the lm3886 circuit
Any ideas on project/kits that could be useful?

[jaycee]

That velleman kit is junk - 200W peak into 4 ohms maybe, but i wouldnt trust it to subwoofer duty.

IF you want kit stuff, look at Rod Elliot's kits, specifically P68 amp and P48 as the filter/processor.

LM3886's are good for about 30-50W power and pretty good quality given the simplicity of the circuit.

Definitely keep the 2ch amp part seperate from the sub. If you use LM3886's, i'd say a 300VA transformer to supply the 2ch amp, and a 500VA one to supply the sub.

[Jan Mattfolk]

I was thinking of 300-500w sub, so the p68 + p48 seems to be suitable.
however, i would like to get 100w/channel on the other amp, so something like 2x BR100, 2x PA100 might just do it. Any recommendations on bridged or parallel?

[AndrewT]

Start with the speaker driver specifications. Particularly sensitivity and power handling.

From there determine the power required in each channel of the active amplifiers.

Then determine the amplifiers required and the PSU & transformer to give your target SPLs.

I would suggest that for one active setup and for future flexibility you build 2channel amplifiers.

[Jan Mattfolk]

I have got my hands on a toroid with two 24 V secondaries, rated total 545VA or 272,5A per winding. It is capable of delivering all the current i need, but the voltages are too low. I´ve had a glimpse at rod elliotts dual power supply (Project 04), and i wonder if it is possible to make a serial connection (connecting one +34 V with one -34V and possibly ground?) between the rails and then get 136V ct (68-0-68) after rectification?

[AndrewT]

What's wrong with designing an amplifier to work well with +-35Vdc supply rails?

[Jan Mattfolk]

excellent question. Because i don´t know how. If you could direct me to some litterature in amplifier design i would be grateful

[tinitus]

Originally Posted by AndrewT

What's wrong with designing an amplifier to work well with +-35Vdc supply rails?

sounds perfect, nice power

[tinitus]

Originally Posted by Jan Mattfolk

My first idea was to integrate everything into the subwoofer (like 2.1 system), but i am realizing it isn´t the right way to go.

I dont see why not

[AndrewT]

why not?

Because too many are influenced by the marketeers/advertisers who make out that how many power Watts or how many Mega pixels make for a good or better or best product.

Just look at the way Car Audio has gone.