Help Please..Question regarding board resistors...

ZEPFREAK · Post by **ZEPFREAK** » Thu Feb 10, 2005 5:34 pm

I'm presently building a board for a 50 watt lead...I was going to try out Vishay Dale metal film resistors because of their noise reduction and value consistancy..I was wondering if I can replace all of the carbon and metal oxide resistors on the board with Vishay Dale metal film..And do they all have to be the exact values..I see a few are 820 ohms..And I think the Vishays are 825 ohms..Thanks for any input..Randy

Flames1950 · Post by **Flames1950** » Thu Feb 10, 2005 10:47 pm

You should be able to substitute the Vishays for any of the resistors you like, as long as the wattage rating of the resistor is correct for each type of circuit.
You shouldn't have any problems if the Vishays are slightly off. Your example of 820 vs. 825 ohms: even if the 820 ohm resistor had a 5% tolerance, that's a possible variance of 41 ohms either way!! I can't imagine you'll notice the difference (unless you're Eric Johnson......

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Billy Batz · Post by **Billy Batz** » Fri Feb 11, 2005 9:25 am

Many people claim the vishay metal films sound warmer. Mohave uses all Vishay/Dale metal films. Theres alot more off values then the 825. The 220k are 221k, the 470R are 475R etc... So like Flames said its nothing. That 1% tolerance could make it anywhere from 816 to 833 while the traditional carbon films with 5% tolerance would make it from 779 to 861 and carbon comps with 10% tolerance would be from 738 to 902. See why vintage amps can sound so different?

ZEPFREAK · Post by **ZEPFREAK** » Fri Feb 11, 2005 2:49 pm

Hey Thanks Flames and Billy Batz..I never go past either one of your posts without reading it!!..You guys are the best...One other thing regarding resistors if you don't mind..You guys said keep with the correct wattage rating..How about the voltage ratings..I heard overkill is ok..What's the lowest rating you could go with..Thanks again guys..Randy

Billy Batz · Post by **Billy Batz** » Fri Feb 11, 2005 4:21 pm

Resistors arent rated in volts. A resistance doesnt just stop the voltage it has to release some energy that you measure in wattage I guess is a way to put it. Most of the board is fine with 1/2W though I use 1W for those when I use anything but carbon comp. Some people use higher wattage for plate resistors and cathode resistors.

Flames1950 · Post by **Flames1950** » Fri Feb 11, 2005 4:26 pm

Most resistors are half-watt stock in guitar amp circuits, except the bigger 10K resistors in the B+ voltage line, they're 1 watters.
Many people like to bump all these up to the next level, ie. one watters in place of the half-watt resistors, and 2-watters instead of the one-watters in the B+ line.
Seems like Matchless didn't use anything less than a two-watt resistor, did they?

Billy Batz · Post by **Billy Batz** » Fri Feb 11, 2005 4:31 pm

I have quite a few booteek schems that show people using high wattage resistors. Maybe theres something to that. It seems Ken Fischer made it a point to use a high 1k25W cement in place of a choke though a 5W would have been sufficiant. Ive also heard ****** say a 5W cement for the cathode resistor sounds creamy in Marshalls.

ZEPFREAK · Post by **ZEPFREAK** » Fri Feb 11, 2005 5:41 pm

Wow...What a bone head I am..I must have been thinking of capacitors when I was talking voltage..Thanks for all the input..I'm going to go ahead and build with the Vishays...Let ya know how it sounds..Randy

Zoso · Post by **Zoso** » Sat Feb 12, 2005 1:35 am

Billy Batz wrote:I have quite a few booteek schems that show people using high wattage resistors. Maybe theres something to that. It seems Ken Fischer made it a point to use a high 1k25W cement in place of a choke though a 5W would have been sufficiant. Ive also heard ****** say a 5W cement for the cathode resistor sounds creamy in Marshalls.

By cement, do you mean those square, wirewound resistors that look like little cement blocks? (I'm guessing that is what the reference is, but I want to make sure)
Also, is this all cathode resistors, or just certain ones?
Thanks!

Billy Batz · Post by **Billy Batz** » Sat Feb 12, 2005 9:49 am

Yeah. The Xicon ceramic encased, cement filed ww resistors everyone uses for screen grids. ****** was talking about using them for the cathode resistors using 1k in place of the 820Rs since in most vintage amps the 820s are CC and drift up past 1k anyway.