Does anyone have, or know of a place to purchase, a 525 ohm 6 watt resistor? I'm trying to build two UL monoblock GEC 88-50's and these resistors are very hard to come by. I've tried almost everywhere on the web and only mouser can come up with a 525/4 watt with a 12-14 week lead time @ $6.52 a pop. Two specialty vendors (US and I can't remember the other one) want $45 a piece to construct them and I'm having difficulty with those prices.
I know I could paralell two to make one, use a 523 or a 536, or even use two pots, but using the original design would be better, I think. Appeciate any help and I do have a few hard to get items to swap if necessary. Thanks.

I don't understand your thinking that it has to be a single resistor of the exact value. The originals were no doubt custom made to the designer's specs and were probably never a standard value. The circuit will not function any differently if you use two resistors in series or parallel to reach the desired value, all it sees is the resistance.

The easiest way out is to purchase an Ohmite 12 watt 750Ω adjustable wirewound resistor, and set the slider to 525Ω. Mouser very likely stocks those.

Can you post the schematic for the amp , the ony thing i know that would have to be that acurate is a cathode resistor , using a 500 ohm 10 watt resistor and a 25 ohm 5 watt resistor in series is no big deal , and woun't sound any different than one 525 ohm 6 watt resistor .I'm as picky when it comes to audio but put your money where it matter in good tubes and transformer when a resistors is going to be bypassed by a cap , the cap is the criticle component for sound quality not the resistor as long as the value is correct . In the amp im curently working on the cathode resistor is 900 ohms 7 watt so im using three 2.7 k ohm 3 watt 1% resistor to come up with 900 ohms at 9 watts no big deal .

Yeah, you're right. After searching for a week I was getting pretty frustrated. I was hoping maybe someone had a few laying around. I'll go with the paralell option. Appreciate the input.

I looked but didn't see anything in my stash.

I wouldn't sweat a few ohms either way. Even 500 ohms would be within 5% and frankly the tubes won't be that good, or would remain that good even if you selected them.

Dennis has the best suggestion.

An advantage of his "sliding-tap power resistor" suggestion is that it may be that for optimal operation in this actual circuit and as determined experientally some value a little less than, or a little more than, 525 ohms would actually be better.

Best,

Fred
repairing audio gear since the Pleistocene

Be sure you hook the slider to one end of the power resistor. That way if it works loose, the resistance
just rises to the full value. If not it could arc, causing much mischief.