Bo's 48v Phantom PSU

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I went for the big one - 48V >100mA

http://w1.316.telia.com/%7Eu31617586/#48%20volts%20phantom%20power%20supply

Am I thinking right - do I just split of the 48v and 0 rails into multiple DC outputs and feed these to separate 48v input of different preamps
And if so how many preamp phantom power requirements can this drive?
If it is 10 then fine - but if it is 100 then this is way overspecced..

www.maplin.co.uk
N09BA 230Vac Toroidal Mains Transformers N08BA 2 x 24V 330VA 2 x 6.88A £27.99

www.rswww.com
261-154 Diode, Rectifier, 1N4002 EACH £0.07
168-7282 IC, Voltage Regulator, HV Adj, TL783CKC EACH £3.20 £3.20
227-8413 Diode, Bridge Rectifier, DF01M EACH £0.18 £0.18
315-1101 Capacitor, electrolytic, aluminium, low impedance, radial, wire ended, 100V, 470uF EACH £1.856 £
315-0962 Capacitor, electrolytic, aluminium, low impedance, radial, wire ended, 63V, 100uF EACH £0.246
191-7892 2 x Capacitor, electrolytic, aluminium, min, wire ended, radial, YXF, 63Vdc, 10uF EACH £0.128
298-0093 2 x Capacitor, polyester, metallised, 5mm, MMK5, 5%, 100Vdc, 0.1uF EACH £0.073
214-1210 Resistor, metal oxide film, power, 1W, 3k3 EACH £0.20 £0.20
214-0992 Resistor, metal oxide film, power, 1W, 82R EACH £0.20 £0.20

I couldn't find any 3K 1 W resistors at RS but went for a 3.3 with 5% tolerance - is that okay
And also - the resistors are metal oxide film - is this okay?

Many thanks
Simon
 
Simon,

You can use a 3,3 kohm, but use a 2 to 3 watt resistor (3,3 k= RS 152-662 or try 3 k= RS 294-3145) because this resistor run very hot, then you must parallel/shunt this 3,3 kohm resistor with a 33 k or 39 k or 47 k resistor (a normal 0,5 w is ok) to get exact 48 volt out from the PSU.

Your choice of transformer is to big, 2x24 volt and around 15 to 25 VA per winding is a more normal choice for this size of phantom PSU (RS 201-7454 or 201-7527 or 201-7606)

(this PSU can delivery more than 100 mA, it is becomes on the transformer, rectifier, the first capacitor (470 uF) and heat zink for the regulator)

You can run a lot of condenser microphones on 100 mA, a normal microphone to day draw aprox. 3 mA (33 microphones= 100 mA) and a Neuman U87 old types draws 0,5 mA and 1 mA for the new Ai types, so you can use 100 of these.

Put a small heat zink on the regulator if you shall use the PSU near 100 mA output current.

Good luck

--Bo
 
Bo
many thanks for your help


Revised parts list

www.rswww.com
261-154 Diode, Rectifier, 1N4002 EACH £0.07
168-7282 IC, Voltage Regulator, HV Adj, TL783CKC EACH £3.20 £3.20
227-8413 Diode, Bridge Rectifier, DF01M EACH £0.18 £0.18
315-1101 Capacitor, electrolytic, aluminium, low impedance, radial, wire ended, 100V, 470uF EACH £1.856 £
315-0962 Capacitor, electrolytic, aluminium, low impedance, radial, wire ended, 63V, 100uF EACH £0.246
191-7892 2 x Capacitor, electrolytic, aluminium, min, wire ended, radial, YXF, 63Vdc, 10uF EACH £0.128
298-0093 2 x Capacitor, polyester, metallised, 5mm, MMK5, 5%, 100Vdc, 0.1uF EACH £0.073
294-3145 Resistor, wirewound, vitreous enamel, 2.5W, 3k0 EACH £0.598
214-0992 Resistor, metal oxide film, power, 1W, 82R EACH £0.20 £0.20
201-7527 Transformer, encapsulated, 42VA, pri 2x0-115V, 50/60Hz, sec 2x0-24V EACH £14.16

554-311 Heatsink, compound, metal oxide, 20ml EACH £3.08
234-2334 Heatsink, 17degC/W, T0220/T03P EACH £1.18

I choose the 3.0k 2.5 watt resistor - I assume the second resistor is an 82R (I am getting a 1 watt one)
 
This may seem a simple enough question
Put I wish to put this into a 19 inch rack with a metal toggle mains on/off switch on the front panel and an LED to show that the mains is on.

I figure that the switch is a simple DPST switch on the live and neutral mains into the primary transformer - with a 5A slow blow fuse afte the switch on the live feed to the primary transformer
The earth from the mains lead I connect to chassis earth.

Where does the LED go - I know it will be after the secondary - but where?
 

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