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10M mullard 12ax7 tubes

juddboz80

juddboz80

Active Member
I stumbled on an old knight amp and a knight tuner. I got it for cheap because it had 5- 10M 12ax7, a 10M 7025, and mullard 7189 power tubes....the tuner had high quality tubes in it as well and it works as it should.
My question is how good are these tubes? Are they similar dynamically to regular mullard tubes? Or is the 10M a special grade tube? I looked for some info but wanted to hear from the pros!
 
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Emission performance is certainly a main indicator. I'd suggest grid leak current would also be up there (ie. in a typical cathode bias circuit, does the anode voltage change if the grid is shorted to 0V compared to just having a standard grid-leak resistor to ground), and then depending on how the tube is used, microphony and heater cathode resistance performance may become important.
 
juddboz80 said:
I stumbled on an old knight amp and a knight tuner. I got it for cheap because it had 5- 10M 12ax7, a 10M 7025, and mullard 7189 power tubes...
My question is how good are these tubes? Are they similar dynamically to regular mullard tubes? Or is the 10M a special grade tube? I looked for some info but wanted to hear from the pros!
Click to expand...

Are these in addition to the ones you posted about this past November?

https://audiokarma.org/forums/index.php?threads/mullard-tubes-value.938955/#post-14312611
 
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