Will using a general noninverting opamp topology for each channel work?
Apr 4, 2007 at 2:35 AM Thread Starter Post #1 of 7

Zuerst

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So there are R, L, Ground for headphone plugs right?

Can I just use a noninverting opamp topology for the R channel and another for the L channel and connect source ground to load ground and go with that?

Or maybe I need to put a capacitor between the source and the positive terminal of the opamp to block DC?

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Apr 4, 2007 at 3:10 AM Post #3 of 7

TzeYang

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what about the power supply? you'll need to create a virtual ground reference, otherwise it wouldnt work.

As for the DC input caps, if the loop is closed (ala CMOY), and your source is not outputting insane amount of DC, it's perfectly fine to skip it. I got 0.00mV of offset from my CMOY + Ipod.
 
Apr 4, 2007 at 3:49 AM Post #4 of 7

Zuerst

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Quote:

Originally Posted by AndrewFischer /img/forum/go_quote.gif
DC will ruin headphones.

Yes you need to block it.

Typical and commonly built non-inverting op-amp circuit:

http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf



Looks like I need two potentiometer based on that schematics? One for each channel?

Quote:

Originally Posted by TzeYang /img/forum/go_quote.gif
what about the power supply? you'll need to create a virtual ground reference, otherwise it wouldnt work.

As for the DC input caps, if the loop is closed (ala CMOY), and your source is not outputting insane amount of DC, it's perfectly fine to skip it. I got 0.00mV of offset from my CMOY + Ipod.



Virtual ground? How about using the isolated ground from an isolated power supply?

I'm probably just gonna stick this puppy on a protoboard. I'm thinking about using a bench top power supply (from my college's engineering lab) to power something like the DCV010512 (http://focus.ti.com/docs/prod/folder...dcv010512.html) and use the DCV010512 to power the amplifiers. Hehe maybe isolated power gives better sound quality?
biggrin.gif
 
Apr 4, 2007 at 4:36 AM Post #5 of 7

achina

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You need a dual power supply, or a single power supply with a virtual ground which simulates a dual power supply. The DCV010512D is a dual +-12V output supply. The DCV010512 is a single +12V supply.

These types of DC-DC switching converters can create a lot of noise. These 1watt models don't put out much current. You may want to look at something bigger.

The outputs being isolated from the inputs is a useful thing if you are doing a virtual ground.
 
Apr 4, 2007 at 4:37 AM Post #6 of 7

Pars

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If you don't want to use a virtual ground, you will need +/- power supplies. Amps such as the Grado RA-1 do this by using 2 batteries in series, and the ground is taken from the connection between them.
 

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