8xlaxx wrote:I'm a newbie to the site. Extremely informative website! An asset to the audiophile community, thank you.
Maybe I haven't searched this topic thoroughly on this site but I think, I might not be entering the correct search. I have a PAS 2 that is unmodified. Has original tubes inside and it works. It is driving an unmodified ST-70 (Bias caps and selenium rectifier replaced with diode).
My PAS 2 volume control starts out pretty evenly as I increase gain,...it's not super loud at all through the range until it hits about 12-1 o'clock position then it starts to crank and really show the expression of my speakers. I saw a brief thread on this topic on another site but no luck on the remedy.
Can a member here assist me in diagnosing what the issue might be? The control pot is smooth with no crackle, catch, hiss, or pop. I can live with it but its a little frustrating when I want to hear something at a moderate volume level but not too low. If the answer is already posted in a thread on the website, please post the link.
Thank you in advance.
Let me put this in a way that will help your diagnosis:
a) If the pot is original, and if this behavior is recent - both are necessary conditions - then the pot is defective.
b) If the pot is original, and if this behavior is ongoing, it may be that you do not understand the function of an Audio Taper pot. Audio taper pots 'come on' very slowly. At 50% of the turn, an audio taper pot may be only at 25% of full volume, and then start to come on far more directly thereafter. So, if the sudden onset at 1:00pm is happening evenly on both channels, that is most likely the issue. Try cleaning the pot and see if that brings back a little bit more moderation.
c) If the pot is after-market, repeat a) and b) - or it may be that the after-market device is not suitable for your application.
But the odds of a simultaneous failure of both sides of such a pot are not large. Certainly possible, but not likely. With the pre-amp off, unplugged and the top off, you could test both sides of the VC using a VOM, even in-circuit. And you could observe for yourself how the taper works. In any case, willy-nilly replacing of the pot without a more specific diagnosis may only repeat the issue, but with a new pot.
There are, also, stepped volume control kits out there that would allow you to custom-taper a pot for your specific needs. One of many sources is linked below.
And don't apologize. All of us here are in different stages, and all of us are capable of learning something new, and all of us have 'been there' at one time or another.
Melrose Park, PA