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-   -   universal chip pre-amp project (http://www.diyaudio.com/forums/chip-amps/146150-universal-chip-pre-amp-project.html)

digi01 19th June 2009 10:36 AM

universal chip pre-amp project
 
there are lots of wonderful opamp manufactured by nsc,ad and ti.i plan to make a universal pre-amp basis on the chips.

design goal:
1,simple configuration,
the unit will use 2pcs universal dual opamp.
2,pure dc coupling,
the unit will not include caps in the signal route.no high(low)-pass filtering,dc block.maybe setup some break points for unstable op.
3,diy friendly,
make the pcb compact,easy install,easy embed.

-zang

Atilla 19th June 2009 02:01 PM

It would be nice to be able to configure the opamps as unity-gain buffers in case you wanted a buffered preamp without gain.

Actually that's something I'm working on right now, but I plan to use dedicated buffer chips instead.

AndrewT 20th June 2009 11:56 AM

DC coupled pre-amp
 
DC coupling requires DC detection and some form of input and/or output muting if the detection activates.

Consider adding a DC servo to minimise the "normal" offset.

Ensure you have adequate RF filtering.

I have now done some smd assembly using To23 and 805 resistors/caps. Don't be afraid to use these sizes. It was relatively easy for my magnifying glass assisted old eyes.

digi01 22nd June 2009 01:43 AM

thanks for the suggestions,hopefully i can completed a backbone of schematic this week.i already have some pcb lay out ieads.

any suggestions?

digi01 22nd June 2009 10:08 AM

2 Attachment(s)
here is the sch.extreme simple?
this is a balance/unbalance design,one gain stage with one buffer output.

Ted205 22nd June 2009 10:26 AM

why have you used an output buffer ?

Atilla 22nd June 2009 04:41 PM

If you want to add a dedicated buffer after the opamp, you might want to consider to put it inside the feedback loop of the opamp. Look at the LME49600 application notes for example, I find it to be more beneficial.

digi01 23rd June 2009 01:49 AM

Quote:

Originally posted by Ted205
why have you used an output buffer ?
the buffer stage was setup for connection friendly,it can fix impedance problem of the after device such as connection cable,volume pot,power amp...


Quote:

Originally posted by Atilla
If you want to add a dedicated buffer after the opamp, you might want to consider to put it inside the feedback loop of the opamp. Look at the LME49600 application notes for example, I find it to be more beneficial.
this is a design case.the u1a,u2a voltage gain is isolated with the u1b,u2b buffer.
i have tested the overall loop configuration.it work good but it is no good for pre-amp.
if i make a headphone amp i will use overall loop.

Atilla 23rd June 2009 06:35 AM

Allright, that's good to know, thanks :)

lgreen 23rd June 2009 09:50 PM

Why are R1,R2, R9,R10 at 950 ohms? Shouldn't they be more like 100 ohms?


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