On Jul 1, 11:43 pm, "Paul E. Schoen" <pst...@[EMAIL PROTECTED]
> wrote:
> <mrdarr...@[EMAIL PROTECTED]
> wrote in message
>
>
news:a1662fad-e0d7-4306-9e20-195abb1e7311@[EMAIL PROTECTED]
>
>
>
> >I was reading the datasheet for the LM1875
> >http://www.national.com/ds.cgi/LM/LM1875.pdf
>
> > and I noticed that they do have a schematic for a single supply (as
> > opposed to a +/- supply).
>
> > If running on a single supply, does the chip amplifer consume
> > significant power during quiet tracks?
>
> > Would this be pretty much the same as running the amplifier in Class A
> > mode (vs. Class AB)?
>
> > I'm trying to figure out if I really need a +/- power supply, or if I
> > can just go with a single supply (easier to build).
>
> > Thanks,
>
> > Michael
>
> Since the LM1875 is inexpensive, you might try using two of them on a
> single supply, and putting the speaker between the outputs. You would
have
> to make one amp inverting and the other non-inverting, but you will get
> twice the output voltage and save the capacitors. A single 24 volt
supply
> will then give +/- 24 volts, or about 17 VRMS, to an 8 ohm speaker, or
36
> watts. There are lots of 24 VDC supplies available. The downside of this
> approach is making sure the DC level of both amps are equal and about
1/2
> the supply.
>
> If you check SemiElectric's eBay store you will find PC boards and kits
for
> the LM3875, as well as other single and dual amplifier ICs:
>
> http://search.stores.ebay.com/semielectric_audio-amp_W0QQfciZQ2d1QQfc...
>
> His LM3875s are about $6.50 each. They are larger (56 watts vs 20
watts),
> but seem to be otherwise quite similar. Most of the additional IC pins
are
> NCs, for heat sinking and mechanical mounting, I suppose. They are only
> $5.90 each from DigiKey, and the LM1875 is $3.28. Wow: 10 to 15 cents
per
> watt!
>
> Paul
That's a good idea. Thanks.
Michael
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