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Old 18th September 2012, 04:22 PM   #1
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Location: Draper Utah
Default I need mini Pre-amp board, please help

Guys,

I have been looking everywhere and can not find a good solution.

I need to have volume control and level gain for a headphone signal to a Icepower amp.

the pre-amp needs to be small and high quality.

I also need it to run of 12-0-12 DC power source.

I found this but it says it needs a AC power source. and it does not come with Opamp. I don't know anything about how to choose a opamp. Do you need to setup a opamp or does it just work?

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

I really need a pre-built solution. But I am not afraid of doing some assembly.

Thanks for your help!!

Mike
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Old 25th September 2012, 12:24 AM   #2
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Can anyone help me here?

Have you heard of this product from ebay or do you know of another solution for headphone level pre-amp thats simple, sounds good, and small?

Thanks!!
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Old 25th September 2012, 01:37 AM   #3
DUG is offline DUG  Canada
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"I also need it to run of 12-0-12 DC power source."
"I found this but it says it needs a AC power source."

I looked at the board and it has 12V regulators on it.

You can supply it with your 12-0-12 VDC supply and it will work.
It just won't have the output swing compared to the source specified.

Here is the datasheet that I found:
http://semicon.njr.co.jp/eng/PDF/NJM4580_E.pdf

I don't know what signal you are feeding it with or the gain it has.

The only problem with it might be too much signal in combination with too much gain.

The other problem may depend on you time requirements:
"Delivery time depends on destination and other factors, it may takes up to 20 business days."

Other than that it looks good. (IMHO)
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Old 25th September 2012, 02:22 AM   #4
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Quote:
Originally Posted by DUG View Post
"I also need it to run of 12-0-12 DC power source."
"I found this but it says it needs a AC power source."

I looked at the board and it has 12V regulators on it.

You can supply it with your 12-0-12 VDC supply and it will work.
It just won't have the output swing compared to the source specified.

Here is the datasheet that I found:
http://semicon.njr.co.jp/eng/PDF/NJM4580_E.pdf

I don't know what signal you are feeding it with or the gain it has.

The only problem with it might be too much signal in combination with too much gain.

The other problem may depend on you time requirements:
"Delivery time depends on destination and other factors, it may takes up to 20 business days."

Other than that it looks good. (IMHO)
DUG, Thanks for your response.

I am taking a ipod into a Icepower 200AC digital amplifier. I am using a Alps volume pot with OK results but I need gain for some ipods and material. Not much gain.

So I was thinking something like this would work. Do think I will have too much gain? is there a better Opamp for my application? The cost is really not the issue here. It needs to be small and sound good. I only need like a 20-30% increase in gain from the source. With a Iphone its pretty good but with a ipod its way too low.

here is maybe a dumb question, Will this also lower the gain and act as a complete volume control or does it just increase gain?

Thanks again!!

Mike
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Old 25th September 2012, 11:14 PM   #5
DUG is offline DUG  Canada
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The pre-amplifier will have a certain amount of gain and the pot can lower the output.

Since the ipod has an output control you should be fine.

If there is too much initial gain then reduce the output from the ipod until it is not distorted. Then adjust the pot for the output required.

I am surprised the ipod does not have enough output to drive the amp.

Have fun.
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Old 25th September 2012, 11:32 PM   #6
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Quote:
Originally Posted by DUG View Post
The pre-amplifier will have a certain amount of gain and the pot can lower the output.

Since the ipod has an output control you should be fine.

If there is too much initial gain then reduce the output from the ipod until it is not distorted. Then adjust the pot for the output required.

I am surprised the ipod does not have enough output to drive the amp.

Have fun.
Good point. I think it will work, Thanks!!

I asked the guy from ebay and he said this wont work with a DC power source. I did some reading that confirmed that it might just like you said. I might not get the gain but that is OK since I don't need much anyway.

Can you tell me the regulator on this Ebay board? Are you still sure it will work with DC source? How do I find out what the current draw will be? I want to make sure my Dc to DC converter has enough output to drive this.

Mike
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Old 26th September 2012, 12:07 PM   #7
DUG is offline DUG  Canada
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The board was labeled 7812.
It is a TO-98 package.

The op-amp is usually less than 0.02A

What is the current output of your DC-DC supply?
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Old 26th September 2012, 02:54 PM   #8
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Quote:
Originally Posted by DUG View Post
The board was labeled 7812.
It is a TO-98 package.

The op-amp is usually less than 0.02A

What is the current output of your DC-DC supply?
My DC to DC is 3 watt at 12-0-12

I am using max 1 watt right now so I have 2 watts left.

Here is a question- Why do I need the regulator if I already have a regulated 12-0-12 power source? couldn't I power the Opamp directly and bypass the regulator?

Mike
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Old 26th September 2012, 04:14 PM   #9
DUG is offline DUG  Canada
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If you are comfortable bypassing the regulators then yes you can.

There may be noise issues but you will have to decide that when you are done.

You can still leave the diode bridge in place (you will only loose about 0.6V) for reverse protection. (and it won't matter which of the two 12V terminals your 12V is connected to.)
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