Bazz Fuss Low Output

[PRR]

> I think the whole circuit draws something like 10-15ma while the LED alone draws something like 20

??

The circuit is a 9V battery to a 100K resistor and then stuff. The MAXimum it can pull is 9V/100K or 0.09mA. If it did that, audio would be horribly mangled. Well, that IS the idea, but realistically not all the 9V is dropped in the 100K, and it is probably 0.07mA.

20mA is a MAXimum for most small LEDs. In most rooms we pick a resistor to pass much less current. 5mA even 1mA are often ample indoors.

Still, the LED probably sucks 14 to 70 times as much as the circuit itself.

The buzz of an un-regulated supply increases with load, and pretty nearly in proportion. Many "crappy" wall-warts can be tolerably low-buzz at 0.07mA. When the LED sucks 50 times more current, the buzz gets 50 times bigger, and that will probably be offensive.

There are many ways to control buzz in audio circuits. Commercial designs may do as little as possible. Until recent decades R-C power filters were used to filter sensitive stages separately from high-power sections. The old-school ways work. However in these modern times when a regulator costs less to make than to ship, and hardly any more than an R and a C, regulated supply makes much sense in pedal-work.

[bassmannate]

Thanks for the info! Yeah, that Spyder supply is looking more and more appealing. I've got parts for other projects sitting on my bench right now but I've been eyeing the transformer with multiple secondaries. Probably going to move to the head of the list of to-do projects. Just trying to work out how exactly to get 12v regulated out of it since I want to build a valvecaster and run the heaters at the correct voltage.