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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Mullard ECC82 - sound muddy and dull posted by ffrr on June 9, 2006 at 00:08:49:
OK, so the reason that an ECC82/12AU7 may sound "muddy and dull" may be related to that very high value cathode resistor, which may be cutting down on the current thru the CF. This may also be why you are able to plug in a 12AX7 without problems (apparently). The 12AX7 and AU7 are so different electrically that one usually should not ever swap them in any circuit designed for one vs the other. Try reducing the value of that cathode resistor by at least half or maybe to 1/4 the current value, this will increase the current thru the tube proportionately, and it ought to make the 12AU7 sound considerably better. Once you do that, the 12AX7 will no longer "like" being plugged into that socket, because the 12AX7 cannot handle much current and has v low max plate dissipation (in Watts = current X voltage). The 12AU7 begins to wake up with at least 3 to 4 mA of current per section; with a 100K cathode resistor you are probably running barely 1mA thru your CF, if that, and only assuming you have a v high voltage power supply. The 12AX7 is a lousy choice for a CF, anyway. This is yet another example where possibly erroneous conclusions are made about the "sound" of a tube (the Mullard ECC82, in this case) due to misuse of a tube in a circuit.
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Follow Ups
- "muddy and dull" - Lew 10:42:50 06/09/06 (2)
- Re: "muddy and dull" - ffrr 16:43:30 06/09/06 (1)
- Re: "muddy and dull" - Lew 13:04:58 06/13/06 (0)
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