Not having exact resistor values

[pbman1953]

I'm going through my SUNN 2000s and I have 3 to 4 values that are off by 3 to 4k, does it matter  ?

[eleventeen]

The snarky answer is "depends on what the original value was supposed to be".


In days of old you would buy a 22K 10% resistor (the regular old R you would buy for a build or replacement) and measure it to find 20.3K to 24K. Sure enough, that's within tolerance-band specs. And almost any tube-amp (or anything else) schematic will have a notation that +/- 10% is OK.


Nowadays you buy an ordinary resistor and often find the value to be +/- 2% or even better.


A 3K variance on a 4700 ohm resistor is...no good. On a 470K, it doesn't matter. That's my main point. If I was refurbing the amp after using it for 20 years, especially a low parts count beast like a Sunn 2000, I would probably go with metal films and even go with next-wattage-up types on the plate resistors, for sure. Older carbon comp resistors that handled  power or voltage or both tend to drift up in value. Maybe you would be replacing your "off-value" resistors because it made you feel better, but if you change the plate load resistors for MFs, it usually DRASTICALLY cuts down noise and hiss. Those 100Ks atop the first tube; the 270K and the 47Ks above and below the 6AN8 triode: Absolutely, and make the 1 watts 2 watts. Make the 1/2 watts 1 (or 2) watts. This is by far the cheapest and most results-producing change you can make on a refurb. I would probably do the 1Ks going to the 6560 grids, too. And the power supply node resistors, chg 2 watts to 3 watts. We're talking just a buck or two here, and all metal films you can get from Doug. Silly to scrimp once the amp is open on the bench.


Probably the biggest of big deals is seeing what you can do about changing out your 6AN8. That's supposedly quite the problematic tube.

[pbman1953]

I have the following values that are off-


All new ones are metal 2%





Asking for - 56K, I have 57K




For the bias resistor- I need 18K but have 20K, would 2 K make a difference in this area?




Asking for 1.5 Meg but have 1.47Meg




What would you go to besides the 68n8?


Thanks

[jojokeo]

Those values are fine, you'll never hear or see any difference. The bias has to be set anyway and won't make any differences. I'd leave the 6AN8a tube alone and get a good replacement if the tube itself is an issue and be done with it. I would leave the amp in it's "stock" condition. It'll work fine for years even if it's your only amp (doubtful if you hang around here for very long?).

[HotBluePlates]

I have the following values that are off-

"Asking for - 56K, I have 57K" - About 2% high

"I need 18K but have 20K" - About 11% high

"Asking for 1.5 Meg but have 1.47Meg" - About 2% low

All of those are "the right value" because 20% tolerance hardly makes a difference. "All new ones are metal 2%" If you're using metal film because you want low noise, that's fine. Just know that such tight tolerance is needless precision.

What would you go to besides the 68n8?

Do you mean you want a replacement for the 6AN8?

Don't replace, buy the handful Antique Electronic Supply has for $8. Or buy some on ebay for slightly more.

[pbman1953]

I do have a back up
I went for the 20K on the bias and all I had to do it tweak the adjustment, all's good


Thanks