[sdiy] cheap BOSS dc adapter replacement?/switching noise PROBLEM?

[Tom Wiltshire]

Hi Dan,

> I want to include a 9v Dc adapter with my effects that will have  
> the Boss style 2.1 mm barrel plug and reverse polarity.
> at around 350-500 ma

I think you might still struggle to get down to $5-$8 unless the  
quantity goes up to 1000s or the quality goes down to "chinese".

Still, I turned up one or two in the right ballpark on Amazon.com.

> It needs to be regulated as well as the Boss adapters (or better)  
> and hopefully cost nowhere near as much

That part at least is easy enough!

> circuit A and B have no problem sharing power. BUT when circuits A  
> or C or B or C or A, B and C share power, circuit C always gets a  
> whining noise.
>
> adding more large bypass caps HELPED BUT not enough.
>
>
> is this a common problem? can some circuits just not share power?

There is no reason why any circuit shouldn't be able share power. In  
practice, maintaining a clean supply of the right voltage might throw  
up some problems, but it shouldn't be impossible.

> or should i look into shielded cable? shielded power cable or audio  
> lines?

I doubt it. It sounds worse than just a bit of noise creeping in from  
an unshielded cable.

> any other options?

What's the load? The situation you describe with two circuits working  
ok, but any three circuits causing a problem suggests that three  
circuits together causes too much load on the power supply, which  
might throw up weird problems. Does the voltage remain at the right  
level with all three circuits attached?

Hope this helps,
T.