Re: Looking for Correct Pots
I'm not sure specifically which is used on the the jem 777, but typically Ibanez uses audio(logarithmic) pots for volume and linear for tone. 500K for each is fairly standard also.
There's no issues electrically if you use audio or linear; 250K, 500K or 1M in either position. Here's an explanation of how it all works...
Linear Vs Audio Pots: Linear is just what it sounds like. The taper on the pot is a straight line. At 3 it's at 30%, at 7 it's at 70%, at 10 it's at 100%. The taper on an audio pot is a typical logarithmic function. As you roll the knob up it has a slight increase from say 1-3, then a larger increase from say 3-8, then it flattens out the rest of the way. The biggest difference is the way the human ear perceives the change. A linear taper sounds more abrupt whereas an audio taper sounds more natural. You'd think it would be the other way around and a straight line would sound more natural, but the way our auditory system works it takes a large change for us to perceive a difference. This is why the audio pot sounds more natural. This is also why audio pots are more typically used for volume. With a linear volume pot it will sound to us like all or nothing. With the audio taper volume pot you will hear the change in volume more naturally. For the tone pot I see both used equally. Some brands like to use linear for tone, others like audio taper. It really comes down to preference and how you use your tone knob. I tend to like using linear taper for the tone pot.
The other part of the pot is the resistance. This is what the 250K, 500K, etc. mean. The short version is the lower the resistance the more highs will be filtered out. In general you will see 250K pots used with single coils and 500K pots used with humbuckers. Sometimes you will see 1M pots but it's not really a factory standard. The resistance of the volume pot usually has more influence over the sound than the tone pots. That's not to say the tone pot has no influence, just less than the volume. You can experiment here if you want and see how it changes the overall sound, but for your purposes I think you'll be best to stick with 500K.
The last thing to consider is the capacitor on the tone knob. .022mfd & .047mfd are the standards, but again you can experiment if you want. The rule of thumb is the higher the value the more quickly the high frequencies will roll off. Unless you want to change out the cap you can reuse the one you have.
You can buy pots pretty much anywhere. eBay, Amazon, stewmac, warmoth, or your local guitar store. They cost about $5 each. As for brands; CTS, Alpha, and Bourns are all pretty good and will fit your needs.
One last thing to note. Pay attention to the shaft length and type of the pot. The shorter shaft lengths are meant for pickguards, long for going through the body and longest for carved tops. Solid shafts are meant for knobs with set screws and split shafts for push on knobs.