bi amping

[felipe_diy]

hello all

I have in mind to build 2 stereo gainclone, one for each channel.
My diy loudspeakers are proac 2.5 clone, with sacn-speak 18w8535 and 2905/9500.
Using 4 transformers I can tweak the voltage for each driver, using only 2 transformers no.
I can choose to use 4x160va transformers or only 2x300va, but which voltage ? 18v ? 25v ?
And which components can I tweak for the treble and which for the bass section ?
Advices are welcome !


--
felipe

 

[dhenryp]

Four transformers or two may be as much a matter of religion as anything else. If there is no cost difference (or you don't care about cost) go with the four transformers. If cost matters, I would not feel bad about going with the two. I would choose 25v for the base speakers, which will give you full output (56+ watts) from an LM3886. You can get by with a lower voltage, and power for the tweeters, 20 volts is probably more than enough. I'm not sure of the power tha will give you but it's probably on the order of 35-40 watts.

You can't tweek gainclone components to get high pass and low pass crossover filters. You need an active crossover. I'm building a two way actively crossed speaker and I'm using the 24db/octave Linkwitz-Riley crossover from here:

http://sound.westhost.com/project09.htm

Read the paper on bi-amping at this site also. It will give you lot's of good information:

http://sound.westhost.com/bi-amp.htm

Good luck.

 

[Peter Daniel]

You can't tweek gainclone components to get high pass and low pass crossover filters. You need an active crossover. I'm building a two way actively crossed speaker and I'm using the 24db/octave Linkwitz-Riley crossover from here:

You shouldn't have any problem with getting 1st or 2nd high pass and low pass filters with tweaking GC components. I don't know about 24db/octave filters, but usually it's not required and doesn't sound as good as simple filters.

 

[JoeBob]

You could set up a passive line level xover before the gainclone, then 1st or 2nd is very simple to achieve, I think this is what Peter was refering to. Planet10 (Dave) has a simple article about this on his webpage, you should check it out.

It would be perfect because you could adjust the gain to make up for the losses and if you make the xover built into the amp the impedances wouldn't ever change.

 

[felipe_diy]

Thanks for the answers, I learned a lot

I like wery much the simple solution that Peter pointed out.

JoeBob, I cant find the document you mentioned, and I need a 3th order LP/HP filter at 3khz.
Is it hard to do ?
While I learn where to begin, can someone give me little more help ?

Thanks all for now

 

[Squalish]

Low/high pass filters can be added right into the feedback loop. Make them toggleable, or adjustable in some way.

 

[SY]

Implementing filter functions in chip amps may be problematic- the amp has to be unity gain stable. There are no doubt some compensation tricks that could be done, but it would be easier and more certain to do the filter functions separately with a more conventional op-amp.