I'm currently building the 1996 John-Linsley-Hood amp (2 for a dual-mono setup).
I've build the regulated power supply from the article but ran into a problem. I've slightly modified the circuit to accomodate a fine tuning to + and - 22V.
The+22V half is ok. only the -22V half is not working ok.
With no load it works ok . With any load (from 470Ohm down to 2*12V20 W lightbulb) the voltage goes to 24.7V or more.
When the base of the power-transistor is not connected the output voltage is nearly constant (until the currentlimit of the 7915 is reached).
The problem probably is due to the totally different internal schematic of the voltage regulators (7815 and 7915).
I've tried so far Thomson and Motorola 7915's and this didn't make any difference.
The measured voltage on the 7915 from gnd=pin to out=pin (with a 470Ohm load from Vout to 0V) is 16,7 V
I've experimented with various NPN power transistors but the result always was an unstable -22V.
As i do not have access to Spice I could use some ideas.
See http:\\www.knoware.nl\users\cfw\amp for my amp site. I'll be posting a circuit diagram of the actual circuit after this.
I've build the regulated power supply from the article but ran into a problem. I've slightly modified the circuit to accomodate a fine tuning to + and - 22V.
The+22V half is ok. only the -22V half is not working ok.
With no load it works ok . With any load (from 470Ohm down to 2*12V20 W lightbulb) the voltage goes to 24.7V or more.
When the base of the power-transistor is not connected the output voltage is nearly constant (until the currentlimit of the 7915 is reached).
The problem probably is due to the totally different internal schematic of the voltage regulators (7815 and 7915).
I've tried so far Thomson and Motorola 7915's and this didn't make any difference.
The measured voltage on the 7915 from gnd=pin to out=pin (with a 470Ohm load from Vout to 0V) is 16,7 V
I've experimented with various NPN power transistors but the result always was an unstable -22V.
As i do not have access to Spice I could use some ideas.
See http:\\www.knoware.nl\users\cfw\amp for my amp site. I'll be posting a circuit diagram of the actual circuit after this.