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PostPosted: 28 Jan 2017, 06:25 
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Joined: 28 Nov 2014, 15:21
Posts: 38
Location: Queensland, Australia.
G'day all, I have a need for a simple low gain stereo line preamp stage to boost an almost line level audio signal up to line level for feeding into a typical amplifier line input. Not a lot of voltage gain is needed, 10 db would likely be more than adequate. Would be simple non inverting op amp amp stage be suitable? Regards, Felix.


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PostPosted: 28 Jan 2017, 10:58 
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Joined: 04 Jun 2008, 20:59
Posts: 3552
Location: Arizona, USA
Hi, Sure, I would use a DC to symmetrical DC converter (I often use ones from Meanwell) to get a symmetrical +/- supply. If you look at my posting of a low cost IC phono preamp you can see how this is done. Use a good IC. I personally like OPA2134, but there are many others that will do the job. Be sure to use decoupling caps at the + and - power terminals of the IC otherwise it will likely oscillate. I personally don't use input capacitors and only output ones. I also don't worry much about DC gain particularly at such low gain settings. It eliminates another capacitor or two and to my way of thinking will thus cause less harm to the signal (everything causes harm).

Good listening
Bruce

EDIT: Here is a version of the preamp with a second stage similar to what you may want.
Attachment:
IC Phono Preamp with Headphone Output August 1 2016.jpg


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PostPosted: 28 Jan 2017, 14:10 
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Joined: 08 Aug 2009, 03:11
Posts: 2161
Location: Chilliwack, BC
Hi Bruce,

The DCW03A is a single output. Are you running the input voltage around and using the converter "upside down"?

Did you mean the DCW03B-12?

Cheers!

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 28 Jan 2017, 15:35 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, Huh? There are two converters in the schematic the PM-05-12 is a single ouput (12 VDC) from AC 100-240 volts input the other is a DCW03A-12. I have one in my hands at the moment (just to check to be sure I didn't goof up) and it is a DC 9-18V input to both + and - 12 VDC at 125 ma. They are pretty cheap from Jameco and hard to beat for what they do...regulated output etc. I have not had any issues with switching artifacts either. Simple filtering cleans that up nicely.

Good listening
Bruce

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PostPosted: 29 Jan 2017, 00:27 
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Ah, NM... I grabbed the wrong spec sheet :blush:

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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 29 Jan 2017, 00:39 
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Joined: 28 Nov 2014, 15:21
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Location: Queensland, Australia.
G'day all, thank you! Regards, Felix.


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