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Old 6th December 2009, 07:40 PM   #1
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Default Dead bug RIAA Pre

Took the opportunity of yesterday's crummy weather to dead-bug a passive RIAA pre using the LM4562 -- I got out the old RLC bridge and went through the component bin to get close to exact values for the network:

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Old 6th December 2009, 07:47 PM   #2
iko is offline iko  Canada
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Love the construction! It hardly can get more real than this Looking forward to the rest of the story.
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Old 6th December 2009, 08:53 PM   #3
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Here's a first shot at the performance:

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I'm using Walt Jung's values from "The Op Amp Applications Handbook".

Last edited by jackinnj; 6th December 2009 at 08:54 PM. Reason: more information
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Old 7th December 2009, 02:54 PM   #4
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THD+N @2kHz is about 0.01%.
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Old 7th December 2009, 05:40 PM   #5
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Cool
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Old 7th December 2009, 08:50 PM   #6
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Awesome! I'm really a fan of p2p, but I have to confess that I never built a true dead-bug design with a ground plane and such. Definitely up next!
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Old 8th December 2009, 04:23 PM   #7
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Nice job. I've also been eyeing this circuit, but haven't gotten around to ordering the parts yet. Have you gotten a chance to listen? I cant tell from the pic, did you build the full dc coupled circuit? I was thinking of omitting the low pass on the output
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Old 8th December 2009, 04:48 PM   #8
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Quote:
Originally Posted by Capt Zach View Post
Nice job. I've also been eyeing this circuit, but haven't gotten around to ordering the parts yet. Have you gotten a chance to listen? I cant tell from the pic, did you build the full dc coupled circuit? I was thinking of omitting the low pass on the output
No, I didn't put in the servo -- yet -- and it is DC coupled. The AD745 is a shown on Walt's schematic is a BiFET opamp and the LM4562 isn't so some belts and suspenders will probably be needed. I will probably have to get the Dremel out and put the servo on the bottom!

Dead-bug on copper is great because you have the ground plane, you have a heat sink and the P2P means that there aren't little gremlins running around on the fiberglas. The easiest way to nail down the opamps is with the ceramic bypass caps on pins 4 and 7.
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Old 8th December 2009, 05:51 PM   #9
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Put a little LPF on the tail -- it could be tweaked a bit -- but this should tame clicks and pops:

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