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

[Barry Klein]

First of all, wall adapters have made several general changes in the last 5 
years or so.
Transformer w/linear regulation or crude regulation
Switching flyback based design, crude regulation
As above, IC-based regulation
As Above, meets EnergyStar Level 4 efficiency
As Above, meets EnergyStar Level 5 efficiency
Now... everything is going to EUP Lot6 efficiency because of some "European
Directive".  This means the supply has to be more efficient - especially in 
Standby mode.
It adds cost to the supply and most product designs....
So given above you should be seeing a lot of opportunities for supplies on 
the surplus market.
If you are a high volume manufacturer you would need to focus on Level 5 and 
soon EUP6.

I'm dabbling into metal detector design right now and they like to use parts 
like the LT1054 to provide onboard
supply levels.  Not the best regulation but you get  a split supply for low 
power circuits that is tolerant of a wide
range of input voltage.

Not sure if 9V or 12V or 5V is the hot spot of wallwart volume.  Price them 
all and judge the cost differences
between them and what it would cost to put such regulators on your designs.

You could try placing inductors and perhaps MLCC capacitors in various 
places on your DC splitter to see
if you can solve the noise issue too.  Could also deal with what grounds the 
various boxes have for input/output.

Barry

----- Original Message ----- 
From: "dan snazelle" <subjectivity at hotmail.com>
To: "synth diy" <synth-diy at dropmix.xs4all.nl>
Sent: Monday, January 25, 2010 6:00 AM
Subject: [sdiy] cheap BOSS dc adapter replacement?/switching noise PROBLEM?


> This is a 2 part question. (all related to DC 9v power wallwarts)
>
> part one is this-
>
> 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
>
>
> It needs to be regulated as well as the Boss adapters (or better) and 
> hopefully cost nowhere near as much
>
> any ideas??? i am not sure how good the regulation really is on the Boss 
> adapter anyway and that leads me to question 2
>
>
> part two is this:
>
> i have been messing around with A circuit that when powered on ITS own by 
> a 9v dc adapter works and sounds fine.
> BUT when it is connected (via one of those power splitters for dc 
> adapters) to a 9v dc adapter that is being shared with a few other 
> circuits, it suddenly starts WHINING
>
> (i am assuming this is either switching noise that is coming down the 
> powerline OR a problem with the power being shared)
>
> oddly, lets say there are three circuits.
>
> 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?
>
>
> or should i look into shielded cable? shielded power cable or audio lines?
>
> any other options?
>
> thanks so much
>
>
> dan
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