6922/E88CC in Parallel Mode without Cathode Resistors?

[tiefbassuebertr]

In the line stage of a valve preamplifier I observe, that there was no cathode resistors - six trodes are direct connectet with one current source (only individual grid resistors are present).
The signal output was located at the six direct connected anodes about one output capacitor.
Such kind of parallel connecting I haven't see until this day.
How high is the risk of great current flow differences between the tubes and how I can this check without cathode resistors?
The only devices with massive used tubes in parallel mode are follow (but all with cathode resistors/current sources for each tube):
http://www.diyaudio.com/forums/tubes-valves/155048-beard-p35mkii-schematics-photo-photo.html
http://www.diyaudio.com/forums/tubes-valves/94403-ear-yoshino-v20-amplifier.html

Thank you for advices.

 

[DF96]

You would need reasonably well matched triodes.

 

[tiefbassuebertr]

You would need reasonably well matched triodes.

what means the marked term exactly and how I can check the current tolerances through the individual tubes without special evaluation-devices for checking this?
in this case exist a second thread in case of this question in general:
http://www.diyaudio.com/forums/tubes-valves/265416-parallel-tubes.html

 

[DF96]

what means the marked term exactly

It does not have an exact meaning - I was being deliberately vague. How much current imbalance you can tolerate is something only you can decide.

how I can check the current tolerances through the individual tubes without special evaluation-devices for checking this?

You appear to be asking how to determine something without using any method for determining it. Have I misunderstood?

 

[rayma]

how I can check the current tolerances through the individual tubes without special evaluation-devices for checking this?

You can make up a socket adapter in a short plastic tube. It should have a female tube socket on the top, and a tube pattern male plug on the bottom.
Inside, all the pins pass through except for the cathodes, which have a small resistor (sized not to affect the operating point very much) wired in series.
Connections to the two ends of the resistor are brought out as test points. Insert this device into the socket of the tube to check, turn the power on,
and allow the current to stabilize before measuring the resistor voltage with a dvm.