<mrdarrett@[EMAIL PROTECTED]
> wrote in message
news:1e6e5d05-ed46-4ff7-a246-35a18c841cd1@[EMAIL PROTECTED]
> On Jul 1, 3:07 pm, John Fields <jfie...@[EMAIL PROTECTED]
> wrote:
>> On Tue, 1 Jul 2008 13:30:05 -0700 (PDT), mrdarr...@[EMAIL PROTECTED]
wrote:
>> >On Jul 1, 12:15 pm, John Fields <jfie...@[EMAIL PROTECTED]
> wrote:
>> >> On Tue, 1 Jul 2008 11:55:35 -0700 (PDT), mrdarr...@[EMAIL PROTECTED]
wrote:
>> >> >On Jul 1, 11:48 am, Don Bowey <dbo...@[EMAIL PROTECTED]
> wrote:
>> >> >> On 7/1/08 11:30 AM, in article
>> >> >>
a1662fad-e0d7-4306-9e20-195abb1e7...@[EMAIL PROTECTED]
>>
>> >> >> "mrdarr...@[EMAIL PROTECTED]
" <mrdarr...@[EMAIL PROTECTED]
> wrote:
>> >> >> > 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
>>
>> >> >> The datasheet does have a "Typical Single Supply Operation"
schematic.
>> >> >> Have another look.
>>
>> >> >Yes, that's what I said. There is a schematic. It's on Page 2.
>> >> >(amused grin)
>>
>> >> ---
>> >> Look at "Supply Current" on page 2 and read: "Power Dissipation and
>> >> Heat Sinking" on page 6.
>>
>> >> JF
>>
>> >Ah, so apparently the chip does not use more power with a single
>> >supply than with a +/- supply.
>>
>> >Is there any reason why I should NOT use a single supply with this
>> >chip?
>>
>> ---
>> I don't think so, but try it and see if it works the way you want it
>> to. If it does you've saved a supply, but if it doesn't it's only
>> cost you a handful of discretes.
>>
>> JF
>
>
> Good point. Thanks.
>
> Michael
I would like to point out that the single supply schematic has a 2200 uF
capacitor in series with the output speaker. In theory, with an ideal
capacitor, this is going to give an 18 Hz cutoff frequency into a 4 ohm
speaker (36 Hz into 8 ohms). A real capacitor will have some internal
resistance. This is going to give a higher cutoff frequency.
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