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Old 6th Aug 2020, 12:20 am   #31
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default Re: Simple Op Amp RIAA preamp 1st lash up

Quote:
Originally Posted by Ted Kendall View Post
The 100nF between rails is all but essential on these chips to avoid instabilities at ultrasonic frequencies, which sometimes show themselves as a mysterious increase in distortion.
Thanks Ted.
I dug out a couple of 0.1uF poly films and soldered direct across the + and - of each 5534, i.e. across pins 4 and 7.
hasn't made any difference so something else is causing the noise. and now I have lost the LH channel.
I also shorted out the 47uF to ground off the bottom feedback resistor as per the original circuit diagram in case they were the problem.
It's late so I'll put it all to bed and have another look in a week or so when back.
I have a feeling I will be rebuilding this beastie from scratch but with a bit more care around my soldering, as I wonder if the noise is a dry joint and as I have been using lead free solder its hard to see as they all look dull.
A.
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