Sorry for the seemingly simple question and searching takes me round in circles.
I have this board
Dual NE5532 Preamp Amplifier Board Module Base on Musical FAX A1 Tone Design DIY | eBay
It has a split rail 12v AC power requirement. What would be the best way to go about this ?
I have 12v ac single on hand for a DAC, and also some higher voltage DC power for 3255 power amps.
I can't find any cheap dual rail 12v supplies. Only single rail such as small low voltage lighting trafos. I have seen the boards that take single dc to dual dc but nothing in ac.
Am I missing something?! It seems improbable one has to invest in a dual rail toroid just to power this thing?!
Regards
James
I have this board
Dual NE5532 Preamp Amplifier Board Module Base on Musical FAX A1 Tone Design DIY | eBay
It has a split rail 12v AC power requirement. What would be the best way to go about this ?
I have 12v ac single on hand for a DAC, and also some higher voltage DC power for 3255 power amps.
I can't find any cheap dual rail 12v supplies. Only single rail such as small low voltage lighting trafos. I have seen the boards that take single dc to dual dc but nothing in ac.
Am I missing something?! It seems improbable one has to invest in a dual rail toroid just to power this thing?!
Regards
James
Not really, I guess a laminated E-core
would suffice. With regulation ( which can be zener type or regulated with IC, like 7812 or else ) any transformer from 12+12 to 20+20 ...21 V. 21+21 V were common in some radios - it required only two diodes instead of four at the price of a center tapped secondary winding. I mean, probably you have it at hand ...Dual voltage from single AC winding, such as 12 V AC, can work too.
Three, 3.7v LIPO cells in series per rail. Pack of 6, 750mAh including charger are just £17 from Amazon.
No mains ripple & noise or hum loop risks and you could bypass all the onboard regulators and diodes.
Or- If you already have a bipolar DC supply, you could connect it at the filter caps, remove the regulators and connect at their output pads, or connect at the regulators input if your supply voltage is high enough. Trace from the AC input to the IC power pins and see just what you have to work with.
How does this work?
But surely.gives DC and I need AC.?
You lost me there I'm afraid!
Interesting thanks!
Make a standard voltage doubler circuit, then you have access to the center tap of the supply.
Add a following RC filter to each polarity before regulation, since the ripple is 50/60Hz instead
of the usual 100/120Hz.
Image Full View | Circuit Digest
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Single phase rectification / voltage doubler.
Connect the single 12Vac winding between the two input terminals. 9Vac will give you +/- 14Vdc.
Eventually use linear regulators to reduce ripple.
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To use batteries you can simply connect them to the AC inputs.
+ 11.1v to one AC input, -ve and the +ve of the other bank to 0v and -ve of this bank to the other AC input. (or vice versa) See photo - not rocket science.
The opamps will work well on + & - 11.1v and a 750mah battery will last for weeks before needing recharging due to the low current consumption. (a few ma).
You may need more batteries in series, or us a pair of 22v Lipo batteries depending on what the regulators are. Or remove them and use 11.1v
+ 11.1v to one AC input, -ve and the +ve of the other bank to 0v and -ve of this bank to the other AC input. (or vice versa) See photo - not rocket science.
The opamps will work well on + & - 11.1v and a 750mah battery will last for weeks before needing recharging due to the low current consumption. (a few ma).
You may need more batteries in series, or us a pair of 22v Lipo batteries depending on what the regulators are. Or remove them and use 11.1v
Attachments
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I think the reservoir capacitors will need rewiring.
The TLE will generate a virtual ground for the opamps, but the way the preamp is probably designed, means the output is connected to them. They would need to connected across the + & - rails so the 0v is only connected to the TLE's output.
Also the existing regulators will be referenced to the virtual ground which is not ideal.
12-0-12 trafo or in my case, I am moving over to Lipo or LiFe04 batteries as they are more affordable, especially the Lipo ones for RC models which are available in voltages from 3.7 to 22.2 and various ah ratings.
Hello,
let me join this discussion, since I am afraid to open a new thread will not trigger any interest..(actually I have, no response so far).
So now that we are talking about regulated PS for preamps, I wonder, as part of the recapping of my old Tascam mixing consol, if I need to upgrade the old JRC78XX regulator ICs to the newer LM78XXA versions. If I have a look at their datasheet I can see that the JRC one have a much beter ripple suppression ratio (ie 58dB vs 70dB), on the other hand the output noise is some triple of the later ones. What is the best approach here? Shall I just follow the old rule of "dont replace that aint go wrong"?
Cheers,
Laszlo
let me join this discussion, since I am afraid to open a new thread will not trigger any interest..(actually I have, no response so far).
So now that we are talking about regulated PS for preamps, I wonder, as part of the recapping of my old Tascam mixing consol, if I need to upgrade the old JRC78XX regulator ICs to the newer LM78XXA versions. If I have a look at their datasheet I can see that the JRC one have a much beter ripple suppression ratio (ie 58dB vs 70dB), on the other hand the output noise is some triple of the later ones. What is the best approach here? Shall I just follow the old rule of "dont replace that aint go wrong"?
Cheers,
Laszlo
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