Tone Control Problem

[Arn C.]

Hello once again,
     Below is a tone control circuit that the treble is ear bleeding high.  I actually have to turn the treble pot completely off to get it to sound almost normal.  If I put the bright switch on, I belive if it doesn't make my ears bleed it will tear the speakers..  way too much treble.  Any suggestions how to knock the treble down a bunch? 
Maybe a cap or resistor blown?  Or maybe a cap or resistor on its way to being blown?
Thanks again!
Arn C.

[Mark Hammer]

1) Make C4 and C5 .01uf.

2) Make C2 470p.

That will make only the highest treble bypass the volume control when the bright switch is on, and will shift the corner frequency of the treble control downward.  If you engage the bright switch, you should get some sheen but not the strident bite that irritates so much.  By moving the treble corner frequency downward, a little bit of treble cut should do more taming. 

Note, however, that with the corner frequency moved downward, when you turn the treble up, there will now be even more squawk.  Which suggests that you may want to consider moving the corner frequency upward, by dropping C4/C5 down to perhaps .0039 or even .0022uf.  This will mean that while turning the treble control down won't kill as much undesired treble as before, turning it up won't be considered a punishment from God or the content of the next posted Al-Qaeda video.

If you want, go deluxe, and make the turnover switchable.  Plenty of high end stereos over the years have had switchable corner/turnover frequencies for the tone controls, precisely because the point where you want to apply boost isn't always exactly the same point where you want to apply cut.  So, they give you a choice.

To do this in a pop-free way in the amp, replace both C4 and C5 with a .01uf and .0039uf cap in series.  You then send a wire from each end of the two .0039uf caps to a DPDT toggle switch (though to save on drilling, you could forego the bright/treble-boost switch and use it for turnover shifting).  When the switch closes the contacts to shunt the .0033uf caps, the turnover frequency drops as those .01uf caps act like .01uf.  Open up the contacts, and the effective capacitance of the two in series becomes .0025uf, which produces a 2-octyave change in where the boost/cut is applied.  It should also produce a bit of a mid-scoop.

[Arn C.]

Hey Mark!
   Thanks for all the information.   I will give this a try and see how it turns out.
Maybe me ears will get a break!

Peace and again Thank you much!
Arn C.