Is there a way to match tubes without a tube tester?

[RnB180]

I am going to buy a lot of 5 tubes

and dont have anything to test them with.

is there an easy way to figure out how to match pairs?

can I just plug them in and pick the two with the most even glows?

 

[KenW]

Just a guess as I'm relatively new to the tube scene, but I don't think that's gonna be enough(checking the glow that is). I'd either get them tested or buy a confirmed matched pair from a reputable source. I've been looking around for a tester but right now, I'm not sure about the brand I should be looking at but even if I was, I'm not seeing a whole lot of these on the market and those I have found are pricey indeed. I feel your frustration.

 

[jamato8]

Yes, you can have someone else do it. The glow is the heater and tells you nothing about the tube except that the heater is working.

Hickok is a good brand. Do not get an emissions tester.

John

 

[RnB180]

are you sure about the heater thing?


and Ive read stories about incorrect bias or power draw that causes the tubes to glow bright orange or red.

my quad eh tubes that are factory matched have different veriations of glow there is one that is particulary brighter then the others.
then I got one matched pair of NOS tubes on ebay, matched by the seller and they both glow evenly.

so there is no way of matching tubes without a $100+ tube tester?

 

[jamato8]

Yes, you can get a glow from that but I was talking about a normal case. If the plates of a tube glow orange or cherry red you got problems. that tube is drawing too much current and there can be a number of reasons why from bad tubes to incorrect bias if bias adjustment is available.

Normally what you see is the orange glow from the heater or a bluish glow (more in the dark) on some power tubes,

John

 

[RnB180]

anyone else know?

 

[jamato8]

One tube can have identical readings of another and glow differently. Why? Because what you are "normally" seeing is the glow of the heater and in any two tubes the amount of heater that is exposed past the plates will differ, so will the amount of "glow" that you see will differ but this has nothing to do with the actual functioning of the tube, how it is matched or tube life.

I have some tubes from 1929 that match perfect (27 globe mesh plates) but one has more of the heater exposed and looks like a beacon at night. It is so bright it looks like a 15 watt bulb illuminating the room. It is so bright that I don't use it becuase it is distracting but the tube is fine, it just has more of the filament (heater) exposed.

For more information try posting over at Audio Asylum under the tube section and ask the question, though it has been asked many times before. You could also do a search over there.

Oh, you could use a preamp or power amplifier to match tubes, taking measurement of plate current, bias current but you really have to know what you are doing as you are working with 100 to 500 volts and enough current to kill, but this is a very accurate way to check tubes as they are "in" the circuit intended for them.

John

 

[utep10]

I would try to find someone locally that has a tube tester.
Especially, a nice Head-fi'er

, should be able to test a few for you.

What type of tubes are they?

 

[Len]

The cheapest way to accurately match tubes is with a mutual conductance tube tester. The way to properly match power output tubes is plotting a curve of plate current and voltage versus bias. Testers with this capability built-in cost well over $1,000. Some of the more advanced mutual conductance testers can do this manually, but these testers still aren't cheap.

You can not just look at a tube to figure out if it's matched. Brightness of the visible heater element will tell virtually nothing. For small signal tubes, get a dynamic mutual conductance tester (and have it calibrated) or send it to someone who has a calibrated tester. For larger power output tubes, find someone who has a curve tracer (and not many people have these).

I should add: If you're only using small signal tubes, don't worry about it much. Nearly all headamps are single ended or OTL, and nearly all use small signal tubes as outputs. Having a mismatched pair won't affect very much and is not dangerous to you or your gear.