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Old 25th July 2002, 12:33 AM   #1
Beggar is offline Beggar  United Kingdom
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Default Class A vs. IC amplifiers for PC audio

Im currently in the process of dreaming up a new amplifier and speakers for my PC, pretty much going for the sub and 4 satellites approach, but im not too sure what to do for the satellite amps, nor am i sure how to spell 'satellites' so im going to avoid saying that from now on and say small speakers instead.

My choices are pretty much this using 2 cone small speakers, I could either use 4 of the 20 Watt class A amps (http://sound.westhost.com/project10.htm) and use a passive crossover in the small speakers, or bi-amp each small speaker channel using 2 IC amps of undecided type (recommendations on type, power rating and crossover point would be really useful) but again with a total power of 20 W

I listen to losslessly compressed music on my PC so its CD quality, and run through an SB audigy, so im not really sure this is good enough to notice much difference in amps anyway, but it would be helpful to hear/read peoples suggestions on which i should do, or if anyone has any better suggestions i would be glad to hear them
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Old 25th July 2002, 02:14 AM   #2
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I'd use the IC based amps. Those are not bad at all, and given that you'll need several channels i think you'd be much happier with that rather than 3 or 4 amps bleeding *EACH* 150-200w of heat in your computer room
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Old 25th July 2002, 04:18 AM   #3
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20 watt Class A amps will draw about 50 watts each, so
it's not quite so bad, about as much as a nice big monitor
or a P4 motherboard.

But maybe a nice discrete Class AB would be a good fit.
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Old 25th July 2002, 09:26 AM   #4
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Uppss Sorry Nelson, my bad, i was thinkin of stereo amps (doh).
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Old 25th July 2002, 09:41 AM   #5
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Hi,

I thought that P10 of Rod Elliot is SE so it will dissipate around 100Watt for 20Watt output. For 4 channels this is a lot of heat dissipation for computer speakers. I also think that 20watt is more than needed for computer speaker which usually are pretty close to the listener. Why not build 4 small (5 Watt ? ) BJT Class PP-amplifiers like JLH's.


gr,
Thijs
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Old 25th July 2002, 01:43 PM   #6
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Hi Beggar,
I'm lately using an early sixties Panasonic tube reciever driving a pair of Boston A40 6.5" two ways, mounted either side of the PC monitor on my corner placed triangular desk.
This amp is tube class AB and about 15W/ch.
External audio line inputs are from a VCR and PC.

The speakers are rated at 88 dBA/1W/1m, and at 15W (approx 100 dBA) give plenty SPL at my nearfield (<1m) listening position, especially for sustained long term listening to music (fm tuner or PC) or video tape or broadcast tv.

At lower (normal) levels this combination gives long term listening enjoyment.

Regards, Eric.
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Old 25th July 2002, 03:22 PM   #7
Beggar is offline Beggar  United Kingdom
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thanks for the feedback dudes, i guess class A was a bit of a silly idea based on the power it uses up (especially considering im a poor(ish) student and i have nightmares about electricity bills) i probably will go with the IC amps, can anyone recommend a good combination of IC's to use for a bi-amped satellite 'channel' (of total 10-20 watts, i use my speakers for my entire room which is fairly big and i like music pretty loud too your right though tschrama it is over kill, but then again i like overkill/being stupid )
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Old 25th July 2002, 07:03 PM   #8
djdan is offline djdan  Romania
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You can chose TDA7294 becouse it is cheap but very well made and the sound it is very good , too .

This is my sugestion : Make one bridge amplifier with two TDA7294 for subbass speakers [ 16 ohm or two 8 ohm speakers in series] and a 24dB/oct band-pass active filter [ 30 - 150Hz ].

Make 4 amplifiers with a single TDA7294 and band-pass 24 dB/oct active filter in front off them [ 150 - 22.000 Hz ].

Make the power supply : Toroidal transformer 400VA - 630VA with 2 x 27 V AC . Use bridge rectifier 25 -35 A and 2 x 10.000 uF for each amplifier and maiby capacitors for subbass amp ( 2 x 20.000uF) . It would be cheap at this voltage .

Put all this to a large hetsink and that all.

You can have a high-end multi channel amp with this performance:
Subbass Amplifier 100W / 16 ohm with only 0.01% THD and slew-rate 30V/uS.
4 Channels x 50W/8 ohm with 0.02% THD .

This all project cost 150 - 200$ plus your work . It is not " to much " becouse if you want a good sound you must have an amplifier with a lot off headroom ( 10 - 20 dB ).
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Old 25th July 2002, 09:50 PM   #9
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I've heard nice things about the TDA7294 too. Implementation of these power ICs is pretty straigthfoward; try Rod's site, there's a couple of IC amp schematics there.

As for the sound, they're good Nothing like a heat-wasting class A, but again, GOOD. I think for your needs such a project would be perfect.
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Old 25th July 2002, 11:17 PM   #10
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Default TDA7294

Quote:
Originally posted by Lisandro_P
I've heard nice things about the TDA7294 too. Implementation of these power ICs is pretty straigthfoward; try Rod's site, there's a couple of IC amp schematics there.

As for the sound, they're good Nothing like a heat-wasting class A, but again, GOOD. I think for your needs such a project would be perfect.
see also
http://www.diyaudio.com/forums/showt...3517#post43517

What Nelson suggests
is too much work
for little gained

I discussed this Chip TDA7294 once,
with John Curl, a super AMP constructor,
He said: "You have made a good choice, groman!"

So on this one I ASSURELY
agree with Argentina
not the YankieMaan of ours.
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