I upgraded the stock pot to an ALPS blue velvet. I am experiencing some slight channel imbalance shifted to the right. More bass resonance and rumble than the left. Also , the with pot maxed out to full there's no humming, however when i back it off to any other value there's a low hum in the right channel. I've checked all the solder points and my measurements are accurate to what is stated in the manual. Is this a tube related issue?