B1 Buffer Preamp

[Itsmee]

That would be perfect

[tinitus]

OK
many thanks

need to buy a few parts now
I have small 2x22Vac C'core trafos, so I will use regulated supply
and maybe a bunch of small caps after that

[udailey]

Tinitus
I havent built this but the 150k resistors might make it hard to use. I suggest try trimmers there first, then replace with resistors. Good luck. Looks like a fun and educational project.
PS when you first fire it up please have those trimmers at full resistance, then with a DMM on the resistors side of the LDR.. turn the trimmer down til you get desired resistance of 40R on shunt at min volume and no less than 40R on series at max volume. Then you know you are safe and not burning the LED in the LDR.
If you can adjust overall Rtot of your LDR attenuator I suggest trying to go as low as you can and still have whole circuit stable. I enjoy 6k very much. Super detail and transparency down there.
Uriah

[tinitus]

hey, Uriah, my LDR expert man

are you sure it works like the usual LDR curcuit
somehow it looks different to me
att 'voltage' pot looks to me more like a balance pot

would the load voltage to LED's not be more like the difference between positive and negative
or something like that

[tinitus]

found an easy to build regulator
only to find the regulators obsolete
well, maybe lacking precision
and not good at all

and another problem
my 2x22V trafos seems a bit much

[6L6]

Why not parallel the output of your transformer, and use a standard LM317- derived regulator? You only need to get the output voltage down to 22-23 volts.

[tinitus]

Originally Posted by 6L6

Why not parallel the output of your transformer, and use a standard LM317- derived regulator? You only need to get the output voltage down to 22-23 volts.

ah, yes, I was thinking maybe adjustable would be better with the higher voltage trafo

using double secondary(not CT), and double bridge, I can stack two LM317, side by side, to form the +/- supply
this would be ok, right ?

[tinitus]

ah, ok

[AndrewT]

when you use a dual secondary transformer, all the options shown in posts 2985, 2987, 2988 work.
The 78xx series of regulators are still available and do work. An ordinary 317 without the regulation improvements added performs about as well as a 78xx reg.

[6L6]

If you use a full-wave bridge your AC will be smoother and the regulators will be under an easier load. Don't forget to use big heatsinks if you are planning to throw away a lot of volts.