1 op amp should draw no more than about 10 mA. So you could allow for about 50 mA. For an 18V transformer, that would be less than 1 VA. Pretty small.
Here are some ideas for you:
http://sound.westhost.com/project05a.htm
http://sound.westhost.com/project05.htm
Here are some ideas for you:
http://sound.westhost.com/project05a.htm
http://sound.westhost.com/project05.htm
Hi,
check your opamp data sheet.
The Iq is the current draw when no signal is being sent through the opamp.
Check the maximum output currents (+ not = -).
Add these currents Iq +max *2 for a dual and you will come up with about 70mA to 100mA.
Some of this peak current comes from the smoothing caps and bypassing, so you could manage with a smaller average current transformer.
However, I recommend +- 15Vdc from a 2 times 15Vac @100mA as a minimum for a single dual opamp. = 3VA. But I would never use anything less than 20VA and you may find improvements in audio performance by going all the way up to 160VA.
check your opamp data sheet.
The Iq is the current draw when no signal is being sent through the opamp.
Check the maximum output currents (+ not = -).
Add these currents Iq +max *2 for a dual and you will come up with about 70mA to 100mA.
Some of this peak current comes from the smoothing caps and bypassing, so you could manage with a smaller average current transformer.
However, I recommend +- 15Vdc from a 2 times 15Vac @100mA as a minimum for a single dual opamp. = 3VA. But I would never use anything less than 20VA and you may find improvements in audio performance by going all the way up to 160VA.
Hi AndrewT
I sent my order on Sunday evening.Hope I didn't order too small transformer
.
I wanted the outer diameter to be as small as possible,so it will fit nicely in a plastick box I have.
It is 18-0,0-18V 2.3Va(encabsulated model), will be regulated to 15V.
The op-amp will "take" 90mA (4.8+40mA x2)
This transformer will be used only to power the dual op-amp in analog outstage of cheapo Sony DVD player.(the original op-amp receives uneven voltage to V+ and V- ).
If I have understood correctly this transformer is acceptable,but bigger would be better for the sound quality?(good to know for the future projects).
I sent my order on Sunday evening.Hope I didn't order too small transformer
.I wanted the outer diameter to be as small as possible,so it will fit nicely in a plastick box I have.
It is 18-0,0-18V 2.3Va(encabsulated model), will be regulated to 15V.
The op-amp will "take" 90mA (4.8+40mA x2)
This transformer will be used only to power the dual op-amp in analog outstage of cheapo Sony DVD player.(the original op-amp receives uneven voltage to V+ and V- ).
If I have understood correctly this transformer is acceptable,but bigger would be better for the sound quality?(good to know for the future projects).
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