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Post by somethingcool on Mar 6, 2009 11:09:57 GMT -7
installed the 12ay7 in the pi slot where 5751 was originally. positive side was dramatic increase in clarity and headroom like crystal but the amp gets kinda hot temperature wise and slightly less omph(power) more spanking sound its balanced and stuff but ya guess my question is does it afect amp in any bad way? also noticed the rest of the tubes glowing more brightly no red or purple lights thank god lol but ya more like a flashlight is it safe for the components tubes caps etc etc?
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Post by myles on Mar 6, 2009 17:04:26 GMT -7
It is safe. The 12AY7 has a bit more plate current than a 5751 (1.0mA) or a 12AX7 (1.2mA) at 3mA for the 12AY7 but that is not of any concern. A 12AT7 as an example is 10mA and in fact some 12AX7s and 5751M tubes by GT exceed 3mA quite often as they are generally far off design spec. If you like the tone then it's probably fine but you may want to check with the Doc as V2 in the phase inverter in a Carmen Ghia is fixed bias rather than cathode biased so perhaps it may be running too hot. I assume this is a Carmen Ghia but if it is not and is a Mazerati then the 5751 in that case is cathode biased unlike the Carmen Ghia. 12AY7: Plate Voltage ................................. 250 V Grid No. 1 Voltage ............................ -4 V Amplification Factor ..........................40 Transconductance .............................. 1750 µ Plate Current ................................. 3 mA
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Post by somethingcool on Mar 7, 2009 3:41:08 GMT -7
its a z28 head.
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Post by myles on Mar 10, 2009 14:41:13 GMT -7
You will be fine. In Gary Hooker's (Brad Paisley) Z-28 I have used a 12AY7 at times for more clean headroom.
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Post by John on Mar 12, 2009 9:40:45 GMT -7
I didn't know the Ghia was fixed bias!! I just assumed it was cathode biased.
So the old Mazerati amps (being cathode biased) aren't really double Ghias? (and I think I read somewhere the negative feedback is handled differently...probably from a Myles post)
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