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In Reply to: RE: That makes sense... posted by sherod on June 24, 2016 at 08:21:46
The Left Channel is R4 & C9/10/11
The Right Channel is R5 & C12/13/14
In the de-emphasis circuit is it important that the .0039uf polystyrene caps are of audio quality or is the main importance the precise value in order to get as close to 75us? Thanks.
Not to start a was here but in "general", please note the qualifier, any film & foil cap like the poly styrene, or polypropylene, even mylar are better than a lytic. The ones in there now are 5% mylars. IMHO any film cap that gets you to the total capacitance required, for the size of the resistor, so you end up with 75Ás will be fine.
Let the flames begin.
Everyone has their favorite caps when it comes to sound. I'm aware that the factory caps are mylar, but I was only questioning if the cap was more crucial to audio vs. just a decent cap that had the required capacitance to combine with the resistor value to come as close to 75us as possible. I have ordered some polystyrene film and foil as that is what I saw you used. If the stock caps are on spec then I might just leave them in as the tuner sounds really good right now. I have read that mylar does have a tendency to go out of spec with age. That's my next project. Thanks!
No worries, rest assured that the flame quip was not directed at you, and to answer you question directly, which I failed to do , yes any polystyrene will do, the concern here is the total capacitance vs. resistance.
Since I had the 18 out on the bench and I'm an incurable tweak I had the audio board out and was just looking at the condition of the solder joints in general. To my surprise I found a bunch of cracked joints at the blue board connector at the bottom of the board. Had to re-solder about a third of them. Which put me on a witch hunt on the rest of the boards.
You should check yours also and see if its just mine or a generic issue. Don't forget the power supply.
Thanks for the heads-up. I will definitely check the older solder joints. I have done everything except to check out the de-emphasis setting on the caps and resistors. It sounds so good now that I'm hesitant about changing anything. I'm an incurable tweak as well and I can't tell you how many times I've had things sounding great but made some changes for the worse and sometimes too many changes can make it very difficult in finding the change that made the sound worse. I have learned the hard way to make small changes, listen for a while and if the change is better, move onto the next change.
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