Modification of Tweety

“Tweety”

Last modified: October 31, 2006

Tweety needs yellow caps ...

It's now about two years since I finished Tweety, and I still like its sound. And therefore I might not have had the desire to enhance its performance if not at some moment a few weeks ago I found out that one of the the big Jensen capacitors at the output was leaking oil. Now that was an unpleasant surprise. And I needed to replace both capacitors as I did not have another blue cap, only two yellow jensens of 0.33uF. Hmm, this gave me a reason to make modifications to the RIAA circuit of Tweety as well. As shown on the RIAA background page for Tweety, the modified values for the filter would bring Tweety withing 0.1dB of the ideal curve, which is about 10 times better than the original version. Therefore, I changed the 120k resistor for 105k, the 10k resistor for 11k, and the capacitor of 8.2nF for 7.2nF. Well, this last value is not a standard capacitor value, but by putting two caps of 3.3 and 3.9 nF in parallel, we obtain the desired value. This is a copy of the figure of page 4 of that RIAA background article. Clearly shown if that both calculation and simulation of the new RIAA filter for Tweety improves the response a great deal over the original chart.

This is the photo of the new guts of Tweety. I should have known that the canary needed yellow caps instead of blue ones. Don't know why I ever tried the blue ones. Hmm, I'll have to wait a few days before being able to judge the sound of Tweety. Not that I think that the new filter makes a large difference for the sound as far as we'll be able to hear, it's just that it's much more accurately following the RIAA curve.

Anyway, should you have the Blue Jensen caps yourself, be careful and check these caps for leaking once in a while. I read about this problem before on the web, so apparently I'm not the first and only person where this problem is occurring. If you want to stay on the safe site, use Auricaps, they're dry and very very good.

© Maarten&Annemarie, October 2003, 2006