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Quad II tubes replacement

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assimaki

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Joined 2008
Quad Ii Tubes Replacement

Hi,
I am trying several tubes to a Quad II pair.
I tried 6L6G, Russian 5881 (6p3n), GEC KT66, EL37, and I will try also the EL39.
It seems that EL37 sounds better than KT66, KT66 better than 6L6G, 6L6G better than Russian 5881 (6p3n).
The cathode resistor was a 180 Ohm /3W. I replaced for a 180 Ohm/5W.
I was looking for information in data books and I find that the suggested cathode resistor for the original KT66 is 160 Ohm, same for the 6L6, 120 Ohm for the EL37 and no info about EL39.
I suppose that when I am using EL37 I have to change the 180 Ohm cathode resistor for an around 135 Ohm (180/160*120).
What about EL39, is 135 Ohm the correct resistor?
What about 6550, is it suitable?
I will try also to replace the EF86 for EF37A, has anybody the experience?
 
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