Convert mini Pre-amp from AC to DC power

[ExtraCredit1]

hey guys I have this mini Pre-amp I want to use in my portable speaker system but it will not work with DC power source.

Anyway to modify it to work on DC?

It said only AC on the description but I figured I would try it.

P7-MINI Preamplifier Board Top Pre-AMP Headphone DIY KIT FOR MX50 L20 L6 NE5532 | eBay

Thanks!!
Mike

 

[sofaspud]

The preamp itself runs from regulated +12 & -12 VDC.
The extent of power supply mods depends on the main energy source.

 

[AndrewT]

Remove or short the To92 regulators.

A pair of 12V batteries.

6 series connected lead acid, or 10 series connected Nicad, or 10 series connected Nimh, etc.

 

[ExtraCredit1]

The preamp itself runs from regulated +12 & -12 VDC.
The extent of power supply mods depends on the main energy source.

The manufacture says AC and I hooked up DC and it would not work.

 

[ExtraCredit1]

Remove or short the To92 regulators.

A pair of 12V batteries.

6 series connected lead acid, or 10 series connected Nicad, or 10 series connected Nimh, etc.

OK I guess this makes sense, so I don't need the regulators?

I have a +12 0 -12 DC power source.

 

[ExtraCredit1]

when you say short them or remove them how would I short them? they have 3 terminals. which of the 3 would I short?

MP

 

[sofaspud]

Remove the 2 regulators and solder the new power supply wires where the regulator Output and Ground pins were. Refer to the datasheets; the 2 regs have different pinouts.

 

[ExtraCredit1]

Remove the 2 regulators and solder the new power supply wires where the regulator Output and Ground pins were. Refer to the datasheets; the 2 regs have different pinouts.

K, thanks!! Just to make sure I get it, I remove both regulators completely then feed my power source to the output pin of where the regulator was? put +12 and ground on one and -12 and ground on the output pin of the other regulator?

So the power comes in and goes to the regulator then goes to the op-amp? by doing the above I am bypassing the regulator and sending power directly to the op-amp?

Mike

 

[sofaspud]

yes and yes

 

[nigelwright7557]

The manufacture says AC and I hooked up DC and it would not work.

It could be the AC adaptor is providing positive and negative voltages and simply plugging in a single phase DC supply wont work.

 

[ExtraCredit1]

I tried to bypass the regulator and that still does not work. I bypassed the pre-amp to make sure my source and amp were working and everything is good. I also checked my supply voltage and its perfect.

Hopefully there is some way??

Or I guess I need to find another solution. I need a small pre-amp for my amplifier.

MP

 

[sofaspud]

You must be doing something wrong, or something is being overlooked by someone.

I took another look at the preamp board - bridge rectifier, feeding the 78L12 and 79L12 regs, powering the single DIP8 op amp package. Sorry, but my money's on the former.

 

[AndrewT]

blown opamp due to error in trying to connect the wrong PSU at the start.

 

[ExtraCredit1]

You must be doing something wrong, or something is being overlooked by someone.

I took another look at the preamp board - bridge rectifier, feeding the 78L12 and 79L12 regs, powering the single DIP8 op amp package. Sorry, but my money's on the former.

Sofaspud,

Are you saying it should work with DC power supply? Or do you think its possible that I blew the op amp like AndrewT says?

Mike

 

[sofaspud]

It is made to work with DC. This mod was only providing the DC differently.
It may be possible. I don't know what you've hooked up to the circuit trying to get it to work.

 

[asilker]

I ordered the same kit and I'm trying to figure out how to power it. As I'm new to electronics, I'd be interested to hear if you figured this problem out.

My plan was to power the board with a laptop power supply, but it seems the DC voltage is not compatible with the stock board and I should look for a 12-0-12 power transformer with low amp rating?

help I'm an electronics baby!

 

[richie00boy]

To use a DC source such as a laptop power brick you need either a negative rail generator or a supply splitter.

Or a 12-0-12 transformer. The board already has bridge rectifier and smoothing capacitors.

 

[asilker]

To use a DC source such as a laptop power brick you need either a negative rail generator or a supply splitter.

Or a 12-0-12 transformer. The board already has bridge rectifier and smoothing capacitors.

Thanks for the clarification. I just ordered a 12v-0-12v transformer. I'm really excited about trying this project. I'm a little nervous that none of this will work and I'll have to scrap it, but I'll be awfully proud of myself if I can make a functional piece.

 

[theAnonymous1]

Isolated DC-DC converters in handy for applications like this....

Astec Dual DC DC Converter 9 18V 1 23A to 12V 230mA AA05E 012L 120D | eBay

Some external filtering cleans up the small amount of ripple/noise quite well and their small size is a bonus.