15V for opamps from 35V ?

Before I build it, did you hear the difference between this and a simple 7815/7915 ?

I wouldn't think so, considering opamps rather good ability to reject powersuply noise.

for a discreet design, i would agree, but opamps? no, i would just stick with the 78\79xx.
if however your standards are a tad higher, go for the lm317\337 series regulators. they have considerably better specs.
they need reference resistors though.

my thoughts
Marius
 
granted i'm still just the new guy here, i have a little insight to this problem. i have been repairing Peavey amplifiers for a little over 3 years now. i'll use the CS series as an example their rails are aprox +/- 59 VDC it's split like this, the output gets the full +/- 59 then there is a series resistor the next stage goes to the driver board for the driver output transistors. they drop the voltage a little more then there is another resistor to drop it to the final range. (looking at the schematic now) for their needs they use a 10 watt 10 ohm and then a 5 watt 1k. but case and point series voltage dividers are probably the safest and cheapest way to go
 
A few years ago I modified a Crimson Elektrik moving coil head amp's 15v power rails. I tried a zener + transistor (noisy), 7815's (extremely noisy) and ended up with LM317's fed from 50v via a dropper resistor plus filter caps as by far the quietest and simplest supply. Any hiss from the regulator got straight through the discrete mc circuit and was very audible, and decoupling caps across 7815's doesn't do a thing to reduce it either. LM317's are the way to go.
 
sbrads said:
LM317's are the way to go.

now correct me if i'm wrong but don't LM317's use the same PWM style as 78xx series regulators. which means they should have the same harmonic output at X voltage. it was my understanding that the only difference with the 317's was that they were variable. and that much like triacs they only varied the pulse width.


like i have said before i could be way way off but that was what i always thought

Adrian