Biasing the 1ohm resistor way.

[Ronsonic]

A couple of comments here.

I like using 1/2W 1R resistors for this job. The 1/2W will do you the favor of acting like a fuse and blowing if a tube shorts or there's a bias failure.

Nothing wrong with using a 10R except it is enough to begin to affect amp operation. Just as a raw example, let's say you've got 6L6 biased up at 35mA. That will give you 0.35V reading. When you play, the current through the tube will increase (assuming a class AB amp which they pretty well all are) and the increased current will raise the drop across this resistor which will move the bias point of your amp. In our example you'd go from the negligible .35V to over a volt. This will have a compressing effect. Not a bad thing, but it is a thing. The effect is minimal if you have a resistor on each tube, but if you are running, say, four power tubes with one cathode resistor then this will be audible, or more, feelable in the response of the amp.

By the time you get to a 100R, you are really changing the behavior of the amp. Even if you bypass it with a cap the bias point will be all over the place. In that case, with a resistor for each tube, you're going from a static 3.5V affect on your bias to over 10 volts. That's a lot. This starts behaving like a cathode biased amp. And you damn sure need a cathode bypass cap on it or things will start acting very crazy in there when you play.

Even very good meters, including a lot of Flukes have a hard time with very low resistance values. Just get the 1% resistors and consider it good.

These amps do not care about fractions of a milliamp of static bias. If you are biasing to some point that is so close to a threshold that it makes a difference you are doing it wrong.

[nee]

Even very good meters, including a lot of Flukes have a hard time with very low resistance values. Just get the 1% resistors and consider it good.

These amps do not care about fractions of a milliamp of static bias. If you are biasing to some point that is so close to a threshold that it makes a difference you are doing it wrong.

Thanks Ronsonic. An informative post all round, and your last two paragraphs pretty much answer my original question.

[C Moore]

Even very good meters, including a lot of Flukes have a hard time with very low resistance values. Just get the 1% resistors and consider it good.

These amps do not care about fractions of a milliamp of static bias. If you are biasing to some point that is so close to a threshold that it makes a difference you are doing it wrong.

Thanks Ronsonic. An informative post all round, and your last two paragraphs pretty much answer my original question.

You beat me to it. What Ronsonic is saying makes perfect sense to me. I do not have enough knowledge to pronounce his statements as definitive, but I am going to run with his advice. 1%, 1 ohm, and I will get on with my life.
Thank You All

[Ronsonic]

Even very good meters, including a lot of Flukes have a hard time with very low resistance values. Just get the 1% resistors and consider it good.

These amps do not care about fractions of a milliamp of static bias. If you are biasing to some point that is so close to a threshold that it makes a difference you are doing it wrong.

Thanks Ronsonic. An informative post all round, and your last two paragraphs pretty much answer my original question.

You beat me to it. What Ronsonic is saying makes perfect sense to me. I do not have enough knowledge to pronounce his statements as definitive, but I am going to run with his advice. 1%, 1 ohm, and I will get on with my life.
Thank You All

The thing to watch for is not a defective or drifted resistor, but one that came from the wrong bin. It is very rare for a new 1% resistor to be out of spec, never seen it. It is not an uncommon problem to get them jumbled in storage or on the bench and pick up the wrong thing. My Fluke 8050 does fine on low ohms measurements like this, my 27 not so much, even zeroed out it'll read a 1 as 1.6 or so.

I don't claim guru status, but I do repair amps and other music electronics as my day job.

[Structo]

A couple of comments here.

I like using 1/2W 1R resistors for this job. The 1/2W will do you the favor of acting like a fuse and blowing if a tube shorts or there's a bias failure.

That makes complete sense.

Unfortunately, I already ordered and received the 3 watt ones.....

Currently I think the ones in the amp are 1 watt. The Brown Note BOM calls for a 3 watt but the ones in the amp are much smaller than those.

What had happened on my amp is one time I was adjusting the bias and had my meter probes inserted into the test jacks and I bumped the left probe with my hip and broke off the probe tip in the jack!
I tried everything to get it out and ended up installing a new jack.
So the 1 ohm resistor on that side got pretty mangled with a lot of the ceramic getting broken off around the leads.

Oh well, I'll just leave it as is right now.

[drz400]

A couple of comments here.

I like using 1/2W 1R resistors for this job. The 1/2W will do you the favor of acting like a fuse and blowing if a tube shorts or there's a bias failure.
.

True but I learned the hard way that some people will get pissed off if that resistor blows, they put a fresh set of tubes in and bitch at you from Europe cause they didn't know it was there and the amp still isnt right. So for that reason I would prefer to let the fuse do it's job or fuse the cathodes