Hi!
More experimenting...
I rebuilt the Marton circuit attached in the message , with a rectifier buffer, on a test board, so i can pull out wires, change them etc..
I had no 2n3904/2n3906. I used BC547/557, and also try MPSA42/92. no difference in behaviour.
1. The ref divider i used is 1k2/3k6. I played a drum loop because i was sick of the 1khz tone...
2. In the original circuit pin 9 is tyed to pin 11. leaving pin 9 not connected does not change anything. When the signal level is within the range of the lower string of leds, these leds light up normally. When the signal goes slightly above, to the upper string of leds, then the upper leds go steady but the lower leds blink. I could make all the leds of the upper string light up, but the lower leds did not light up steadyly... not even changing the 220R to 100R...
2.1 Tying pin 9 to pin 3 (vcc) stabilizes the supply to the lower string of leds, but at the price of "starving" the upper led string. Even at full level 3 leds of the upper string can't be light up. If i pull out this connection, all upper leds light up nicely, but lower leds can't get steady...they are switching with the signal level.
I expected to save some milliamps building it into a 500 series preamp. But no luck by now...If anyone has a clue what could be done, here I am.
Thank you very much!!
Jay x