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Could anyone give to me information about the methods for matching the power tubes ?
Or give me a website about this subject ?
Around which values matching must be done ?? on which working ( bias) point, and according to which criteria? are several matching bias points necessary ?
If I buy tubes which were matched around a working point different of that one of my amplifier, would there be risks of an unbalanced push pull ?About the criteria, is matching done only with the three following values : plate voltage, grid voltage, plate current ?
Or is it necessary to take the transconductance into account ( consideration ) ?Could anyone give me information or websites which speak about this subject?
I have batches of 6CA7 GE and 6550GE which are not matched.
Thanks
Follow Ups:
Hi:
I use a custom matcher that I built. It has six sockets with a very stiff power supply. Plate voltage is 460V or 350V switchable, grid bias is adjustable.I test EL-84's at 350V, and 6550, EL-34, 6L6, 6V6 etc. at 460V.
I let the tubes heat for 15 min before applying B+, then take current readings.
Note that this does not measure transconductance, only current. I use a Hickok 600A to measure transconductance. Ideally, tubes should be matched for both current and transconductance.
Early on, I found that I was getting various readings at different times of the day. This was because of AC line voltage variations. I now operate my test bench from a Sola CVS voltage regulator, which outputs a steady 122VAC regardless of load or line voltage input. I now get consistent, repeatable tests.
This system has worked good so far.
Hope this helps! Al
It is very interesting.
Many thanks for your help.
jug2hurta. hi. This is a complex subject. You might do a search on how current tube suppliers/branders match and grade tubes. Mutual Conductance is a norm. Keep in mind that brand new tubes as factory matched will probably change (sometimes in a big way) in a mere few hours of operation. To really test a power tube you need to put the tube under dynamic conditions with appropriate B+. A lot of tube testers don't do this. I probably should say Most Tube Testers don't do this.
Also, power tubes do best when run a bit over time and not sitting in a box. An ancient power tube manufactured in 1928 for example should not be subjected to full power conditions on startup. Rather it should be run gently at first and gradually brought up to full power unless you like playing Russian roulette with irreplaceable antiques. Running the tube aids in cleaning up the interior and makes for a happier tube overall.
Hi elektron.
interesting
Thank you for these caveats.
I will be careful.
Enter the single word match into this forum's Text-to-Find box at upper right of forum page & read return #14 to begin with. Next, take off your caps lock as such internet SHOUTING will not garner greater notice but may turn away potentially informative responces due to impoliteness.
Ok,thank you and please excuse me for using capital letters.
I thought that my title would be badly visible.
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