[sdiy] Re: crystal clear

[Magnus Danielson]

From: Don Tillman <don at till.com>
Subject: Re: crystal clear
Date: Wed, 7 May 2003 16:51:59 -0700

>    > Date: Wed, 07 May 2003 21:44:21 +0200 (CEST)
>    > From: Magnus Danielson <cfmd at swipnet.se>
>    > 
>    > I think you fool yourself on the simplicity of a common amplifier
>    > and passive cross-over filters. You need a much bigger amplifier
>    > than if you had two smaller amplifiers.
> 
> What, no equations to back this up?  :-)  
> Y'r slipping, Magnus!

I'm trying to convince people with a more common sense type of arguments, but I
could really back it up with formulas if I really wanted. There is a summation
of powers which really isn't very interesting and fairly apparent, so I made it
implicit... but here it is for the necessary bordercase:

Pbigamp = Ptotal = Ptop + Pmid + Pbas + Pcrossover

Ptopamp = Ptop
Pmidamp = Pmid
Pbasamp = Pbas
Ptotalamp = Ptopamp + Pmidamp + Pbasamp

=> Pbigamp > Ptotalamp

Also, the more complex stuff you want to do in the passive crossover, the
bigger loss you tend to get unless you spend quality time on the loss issue.

> (It's really true.  And plugging in typical numbers shows that it's
> far more of an effect than one would assume.)

Indeed. I just didn't have any real numbers at hand.

It's easier to make a few smaller amp than a big motherfucking amp, and I find
that a good argument in many different senses. It is easier to find transistors
which can work with even the worst-case reactance if you make smaller amps than
if you make a big amp.

Cheers,
Magnus