This
PSU is based on a common design using variable precision regulator
i.c.s and provides +15V and -15V outputs.
Some of the benefits of a 723 based design over those using the 7815/7915 are:-
-
MUCH lower output noise,
- Better load regulation, and
- Better line regulation
For the ASM-1 we strongly recommend the 723 design described here or a similarly rated unit. For readers building the ASM-1 on a tighter budget, the 7815/7915 design will be quite suitable.
Specification
- Output voltages: +15V, -15V
- Output current: in excess of 800mA per rail
- Current limiting at around 1.2A
A stripboard design for this circuit has been kindly submitted by Seb Francis (Please note that the pinouts for Q1 (Q101) and Q2 (Q102) are NOT suitable for fitting the transistors directly to the board - you MUST connect using flying leads).
Setting up this module is straight forward.
!! AVAILABLE NOW !!
This power supply design is now available as a pcb and also as a complete kit with all items needed excluding the mains transformer. The pcb has 12 off 4-way buss connectors for star wiring your modules. Heatsinks, mounting hardware and all on-board components are supplied in the kit along with a 1-meter buss cable for connecting your first module or ASM-1 pcb. The pcb measures 133mm x 88mm and is complete with solder-mask and silkscreen.
By adjusting a few component values you can also generate output voltages from around 5V to 20V. So, for example, you could use the pcb to provide you with +5V & -5V, or +12V & -12V, or +5V & -8V etc.
To complete the power supply construction you will need to connect it to a mains transformer. Please refer to these documents for some guidelines:- mains options and transformer options
Visit our shopping page for pricing.
Choosing an alternative Power Supply
If the reader wishes to use a ready-built power supply instead of building their own then we would like to make the following recommendations:-
- Our systems use only +15V and -15V for the main power rails and generates any additional power rails, such as +5V, on the relevant module. Use of these power rails is recommended as it provides the reader with the maximum voltage levels that would be encountered in normal circuits and allows derivation of lower voltage rails easily. For optimum performance and reliability you should be able to set, and maintain, these power rails to within +/-2%.
- The total current rating of the power supplies will be dependent upon the number of modules in the system but you should aim for a minimum rating of 500mA for a basic system.
- To help prevent damage to the system, the power supply should have built-in protection circuits including thermal-shutdown and, of course, fused inputs.
- We strongly recommend staying away from switched-mode power supplies (like those used in most PCs) as they operate in the frequency band of 100kHz to 200kHz and can generate harmonic noise which can interfere with your audio components. Linear power supplies will be more expensive because they will contain at least one transformer. These units will also be a lot heavier, but the benefits are well worth the extra expense.
The MOTM-900 is a medium duty power module with similar specifications to those listed above and is an ideal `ready-built' unit for this system. The ECC version can be easily adjusted (instructions are included) to operate on a 240VAC system.
!
WARNING !
We do NOT recommend readers build their own power supply unit unless
they are fully competent and aware of the dangers of working with
mains power. There are a number of safety issues that MUST be complied
with to ensure that no harm comes to yourself or anyone else coming
in to contact with your unit. The following article discusses some
of these issues.