Power Tube Matching

From that article, it looks like he is saying that the top, 2 digit, number on a tube box will be between 32 to 42.

@tonydennison No that is not what he is saying. If you read the very last paragraph Roger wrote Bias is matched within 4% and Gm (transconductance) within 8%.

So, if I Bob has 3 tubes that all have the first number of 14.3.....what numbers on a forth tube would be considered matched? 17.1, 18.4, 19.0, 25.8, or even 12.3?

The answer is 13.7 or 14.9 using our method of testing. We actually offer even tighter testing upon request. I personally would not accept anything below 14 or above 14.6. So none of the other values in your example offer a good match to the tube labeled 14.3.

Thank you @clio09 for clearifying, Im no engineer.

What tube shop do you run?

Also, not that Im going to try it, but what would happen using mismatched power tubes? Would there be SQ issues? amp damage? And what type of damage?

Thanks

No don't worry so much about the Ip value , as long as it is the same on all four.   Some places will put a sticker on the base of the tube.  Apex tube matching puts a label on the base of the tube with the value as measured on their equipment.   

I have had pretty good luck with the JJ tubes I have had that were Apex matched.   There are other places that fully test and grade their tubes in a similar way

On your amps if they have an LED for bias will be around 50mA when it starts to glow brightly.    I use this when I retube a 6L6 or EL34 based amp. 

I use this 

https://www.vhtamp.com/avtttt2

It is a great tool for adjusting bias and safe because you are not using meter probes on test pads 

Quicksilver has all of the bias values except the Mid Mono so I asked Mike and he said 53 mA for best performance.   That VHT tool is more accurate than the LED , although it gets you close if set to where it just starts to get bright. 

Gm is expressed in Micromhos and generally the higher the better because it suggests the tube is strong.   No guarantee,  some tubes can drift.  Draw more or less current 

That's why amps with individual bias for each tube or auto bias are more able to cope with mismatch.   

@oddiofyl 

Hey the milliamp tester looks like a good thing to have.

I see one on reverb for $100 new. I'd like to find a used one for $50 or $60. I will look. Thanks.

I'm go to send you an IM.