active crossover from a pc soundcard?

bser

Member
2004-10-04 11:26 pm
with my new HT system I'd like to setup I would like to go pretty high end and use a multimedia pc, a while back I was viewing a forum that suggested a 5.1 sound card for a computer could be programed to function as an active crossover. Does anyone have any experience with this or could someone link me to where I could find more info out about this? I know I'm not being very specific but I don't have much to go on. Thanks for any help.
 

bser

Member
2004-10-04 11:26 pm
One other thing I need to ask is what kind of solution do most use as an economical way to provide 11 channels of amplification to an active 5.1 setup, I am happy with the pro amp I have now but the idea of first of all having to purchase 5 of these and put up with the fan noise doesn't suit me. What kind of amplifier solution is popular amoung those with all active 5.1 channel systems?
 
Look at the kx project website to check what boards are supported. I think the Emu boards are, and are rather high quality, but are quite expensive.

I'd look into the various amp kits from 41hz.com or chipamps from BrianGT, at www.chipamp.com

I personally have never tried either, but I really like the design of the 41hz boards (Tripath extremely efficent and good sounding amplifiers), but BrianGT's gainclones are highly regarded to say the LEAST, and either one would do you well.
 

bser

Member
2004-10-04 11:26 pm
I spent quite some time reading over the chipamp.com site. The information posted on there is kind of over my head as I have never even thought about building my own amplifier, however the construction of the amp doesn't appear to be all that difficult, is it possible to build and opperate an amp kit such as this without fully understanding how it works? And also what is the rated power output on such amplifiers be as compared to a stereo amp from onkyo rated at 100x2?
 
You can build a whole lot of things in DIY audio without understanding them when you start, but I almost always end up understanding them when I'm done :)

The rated output of the different gainclones are determined a lot by the power supply you feed them with. I'd look at the individual sheets application guide from the manufacturer and it should have what power supply you need for specified power.

Also most mass market manufacturers rate the power of their amplifiers at 10% THD, wheras most DIY projects rate at <1% THD, so it's hard to compare exactly power rating :)
 

bser

Member
2004-10-04 11:26 pm


The rated output of the different gainclones are determined a lot by the power supply you feed them with. I'd look at the individual sheets application guide from the manufacturer and it should have what power supply you need for specified power.

Also most mass market manufacturers rate the power of their amplifiers at 10% THD, wheras most DIY projects rate at <1% THD, so it's hard to compare exactly power rating :) [/B]



can you tell me the approximate power output of this kit with the included power supply? I don't need an exact number i'm just curious if I need to look elsewhere as I'm looking for an amp to deliver 100 watts a channel for some power hungry HT speakers.kit
 

bser

Member
2004-10-04 11:26 pm
can someone explain the difference between having 1 power supply feeding both channels as in the stereo model, or having 2 seperate power supplies feeding the channels as in the dual mono model? I'm assuming the dual mono has advantages, what are the advantages and how profound are they?
 
The way I see it is the topology is always dual mono since the chip is mono. However, the power supply being split has a couple advantages like isolation, and the fact that each side now has 10000uF instead of sharing it between the two sides, but that is really all that I see.

You'd be better off asking someone more knowledgable in the chipamp forum really though, because I have never built one of these.
 
Dual Mono has the benefit of a heavy current draw or noise transmited up the PSU rails will not affect the other channel. A chip amp has good power supply rejection, so there will be less noise impact. If one channel draws the rail down, it could impact the power available to other channels.

How profound an effect? Most likely subtle with chip amps. Other designs may be profoundly impacted, though. You probably wouldn't notice a difference if you use a single psu for woofer and tweeter amps.

One word of caution - you describe your speakers as power hungry. If this means that their impedance dips to a low value, you might want to consider parallel LM3886s on fairly large heat sinks, at least for the woofers. You want to ensure that the protection circuit does not kick in, which it will if the chip gets too hot or tries to deliver more than its rated current. I had this proble with my LM4780 (two 3886s in one package) on a smallish sink, even at fairly low volumes. Going into protection does not sound nice.

You might also consider driving your woofers with a bridged/parallel quad of chips, which ought to give you around 200W peaks, and be a bit more likely to stay out of protection. Although more expensive than a single chip, it is still probably cheaper suitable than discrete amps.

Take a look at AKSA's offerings, the Leach amp or Rod Elliot's P-101 or P-3A for discrete amp options. I haven't heard AKSA or Elliot amps, but have a strong preference for the Leach over my chip amps, although they were not nearly as refined as the ones you are considering.