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FDP Forum / Fender Amps: Vintage (before 1985) / Resistors 5% vs. 10%

roadhog96

USA / Sesame St.

Mar 2nd, 2017 04:35 PM   Edit   Profile   Print Topic   Search Topic

Any reason that you can think of why you shouldn't substitute 10% resistors for 5%? If it were vise versa then I could see a reason not to.

Hammond101
Contributing Member
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So. Cal. USA

Mar 2nd, 2017 04:43 PM   Edit   Profile   Print Topic   Search Topic

I think you have it mixed up in your question above.

No problems at all subbing a 5% tolerance for a 10%.

roadhog96

USA / Sesame St.

Mar 2nd, 2017 05:51 PM   Edit   Profile   Print Topic   Search Topic

Hey Hammond101, I don't think this is a good sign. I knew what I wanted to write but I wrote it backwards. My mind is starting to go, I hate getting old. Well at least you knew what I was asking and you answered my question. Thank you kindly for that.

Now here's another question. If an amp is designed for a 10% resistors and you use a 5% in its place and let's say down the road it drifts to +8%. Would it still be in spec for the amp even though it's out of spec for a 5% resistor. It would still be in range if it was a 10%.

(This message was last edited by roadhog96 at 07:59 PM, Mar 2nd, 2017)

Peegoo
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The spotlight

looks like a prison break
Mar 2nd, 2017 07:40 PM   Edit   Profile   Print Topic   Search Topic

Yes it would.

Soon as it goes to 11% out of spec, it's outside the 10% tolerance rating.

Pots are the same way, but most used for amps and guitars are not rated. They sometimes go to 20% and beyond.

amphead4

Cincinnati, USA

Mar 3rd, 2017 07:17 AM   Edit   Profile   Print Topic   Search Topic

I remember reading Jack Darr's book about 35 years ago. Jack was a practical man whose primary concern seem to be keeping gear operational. This was before the age of Internet forums where people discuss the nuances of biasing an amp for tone or which capacitors sound better.

Jack said that for many resistors in an amp, the actual value is not critical and the amp would still operate with a replacement resistance anywhere between one half and double the specified resistance. That's -50% to +100% tolerance.

Applying this philosophy to your typical Fender circuit, in a pinch you could send your client out on the stage with a 100K plate load resistor replaced with anything between 50K and 200K. Or the 3.3M reverb mixer resistor could be 1.8M or 6M. Preamp cathode resistors between 820 and 3K instead of 1500.

Hey, it's working! Yeah, it might not sound exactly the same but sound comes out and that's better than one that's silent.

Outside of filters like EQs where exact values are needed for proper operation, the reason for a manufacturer to use tight tolerance parts in all applications is so that each unit rolling off the line sounds exactly like its brother. We've all heard about an amp that just had IT and was special. Why can't they all have IT and be special? Consistency is good!



Hammond101
Contributing Member
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So. Cal. USA

Mar 3rd, 2017 09:55 AM   Edit   Profile   Print Topic   Search Topic

"We've all heard about an amp that just had IT and was special."

How true. Tolerance stacking can be a good thing or a bad thing, all depends. Same theory applies to our cars, computers, appliances and on and on.

Peegoo
Contributing Member
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The spotlight

looks like a prison break
Mar 4th, 2017 05:59 AM   Edit   Profile   Print Topic   Search Topic

And womerns!

Tolerance stacking!



"Hey, it's working!" Back in the 70s and earlier, pretty much nobody paid attention to tube matching. Blow a tube--buy a tube. Remember those TV shop tube testers that were the size of a kitchen stove?

(This message was last edited by Peegoo at 08:02 AM, Mar 4th, 2017)

roadhog96

USA / Sesame St.

Mar 4th, 2017 09:40 AM   Edit   Profile   Print Topic   Search Topic

Oh yah I remember those tube testers. The local Drug store had one that I used when I blew a tube. They sold new ones that were stored in the bottom cabinet. Never heard of matching tubes back then.

I remember using a spare guitar cable to power an Bandmaster speaker cab for my Pro Reverb, never heard about speaker cable impedance. The 1/4" plugs fit the jacks and there was sound. Hey it worked and that's all that mattered back then.

FDP Forum / Fender Amps: Vintage (before 1985) / Resistors 5% vs. 10%




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