On Wed, 4 Nov 2009 11:05:54 +0000 (UTC), "Mike Warren"
<miwa-not-this-...@or-this-csas.net.au> wrote: >D from BC wrote:
>>I suppose power amps in PCs never took off..
>I remember seeing some Compac models years ago that had the power >amplifier on the motherboard.
>I guess the way it is now allows more options for the end user. >I certainly wouldn't want to use an on-board amp.
Why not? Too much noise? (EMI and ground loop) Insufficient power? (Only 12V available with lots of current) Too much Class AB heat in case? (Some Class AB amps do have low power sleep mode.) No knobs to play with?
D from BC wrote: >On Wed, 4 Nov 2009 11:05:54 +0000 (UTC), "Mike Warren" ><miwa-not-this-...@or-this-csas.net.au> wrote:
>>D from BC wrote:
>>>I suppose power amps in PCs never took off..
>>I remember seeing some Compac models years ago that had the power >>amplifier on the motherboard.
>>I guess the way it is now allows more options for the end user. >>I certainly wouldn't want to use an on-board amp.
>Why not?
In my case I run the on-board sound and a multi-channel sound card into a mixer and monitor it with a 200W per channel amp.
>Too much noise? (EMI and ground loop)
Not if designed properly. I've designed a device with 4 x TA7294s and a motherboard in it that passed EMC testing.
>Insufficient power? (Only 12V available with lots of current)
Some of the modern MOSFET amplifier ICs used in car audio do quite an impressive job from 12V, but yes, there are people in similar situations to me that would still need line level signals.
>Too much Class AB heat in case? (Some Class AB amps do have low power >sleep mode.)
I don't think that would be a problem.
>No knobs to play with?
I certainly don't like software volume controls. When the machine is running hard there is an annoying lag.
You forgot "cost", which I'm sure plays a large part in consumer computers. :-)
> Which leads me to believe that powered speakers and classic boxy audio > amps rule these days.
> I suppose power amps in PCs never took off..
> D from BC > Amateur smps designer > British Columbia, Canada > Posted to sci.electronics.design
The main problem would be the power supply, if you want multi channel 10's of watts rms into 8 ohms. The most a standard psu could provide would be the +/- 12v rails, which won't be enough. The +12 is usually in the 10's of amps range, but the -12 is much lower, perhaps 5 amps or less. So, the problem is not a high enough voltage to give the required swing and also available current. The other thing is that a class ab amp, with supply current following the signal, may not be good for the hdd, which tends to like stable power within tightly defined limits.
An external power amp + speakers + sound card line out is a far better bet, imho...
>> Shouldn't this been mass produced dirt cheap ever since PCs played >> movies and music...??? >> Like this.. >> http://www.marchandelec.com/pm48.html
>> Which leads me to believe that powered speakers and classic boxy audio >> amps rule these days.
>> I suppose power amps in PCs never took off..
>> D from BC >> Amateur smps designer >> British Columbia, Canada >> Posted to sci.electronics.design
>The main problem would be the power supply, if you want multi channel >10's of watts rms into 8 ohms. The most a standard psu could provide >would be the +/- 12v rails, which won't be enough. The +12 is usually in >the 10's of amps range, but the -12 is much lower, perhaps 5 amps or >less. So, the problem is not a high enough voltage to give the required >swing and also available current. The other thing is that a class ab >amp, with supply current following the signal, may not be good for the >hdd, which tends to like stable power within tightly defined limits.
>An external power amp + speakers + sound card line out is a far better >bet, imho...
>Regards,
>Chris
For music at my desk,... I seldom peak out at 0.25W per channel applied to my book shelf woofers. (Assuming 4ohm Z) I digital scoped my woofer, cranked volume to comfy level and used display persistence to see V peaks.
A bridge amp on 4ohms can deliver ideally a peak of 12V^2/4=36W. It's not rock concert power but its good enough for me.
btw.. I run a SSD(solid state disk) in my PC. I think a power amp and the ssd will get along fine on the same 12V bus.
> For music at my desk,... I seldom peak out at 0.25W per channel > applied to my book shelf woofers. (Assuming 4ohm Z) > I digital scoped my woofer, cranked volume to comfy level and used > display persistence to see V peaks.
> A bridge amp on 4ohms can deliver ideally a peak of 12V^2/4=36W. > It's not rock concert power but its good enough for me.
> btw.. I run a SSD(solid state disk) in my PC. > I think a power amp and the ssd will get along fine on the same 12V > bus.
If that's all that's required, but the title was 4x15w, which a pc power supply would have trouble with, especially if it's rms power numbers. Also, you won't get 12v p-p. Probably more like 10 volts linear range if you are lucky.
Not that I should nit pick. If it works, use it :-)...
On Wed, 04 Nov 2009 22:42:44 +0000, ChrisQ <m...@devnull.com> wrote: >D from BC wrote:
>> For music at my desk,... I seldom peak out at 0.25W per channel >> applied to my book shelf woofers. (Assuming 4ohm Z) >> I digital scoped my woofer, cranked volume to comfy level and used >> display persistence to see V peaks.
>> A bridge amp on 4ohms can deliver ideally a peak of 12V^2/4=36W. >> It's not rock concert power but its good enough for me.
>> btw.. I run a SSD(solid state disk) in my PC. >> I think a power amp and the ssd will get along fine on the same 12V >> bus.
>If that's all that's required, but the title was 4x15w, which a pc power >supply would have trouble with, especially if it's rms power numbers. >Also, you won't get 12v p-p. Probably more like 10 volts linear range if >you are lucky.
>Not that I should nit pick. If it works, use it :-)...
>Regards,
>Chris
I think you mean 24Vpp.. Ideally a bridge amp on a 12Vsuppy can do +12Vpeak and -12Vpeak on the load. (Supply polarity flipper.) Power is a problem when there's not enough power from the power supply. For ex. My Corsair PC supply has a rating of 33Amps, 12V. My video card uses more power than a 4x15W amplifier at loud clipping. And there are crazy 1000W computer supplies available if one goes power mad.
Some automotive amp modules claim rail to rail operation. Guessing 11.5Vpeak.
