#1
Ok, so due to me not paying attention, I won an ebay auction that had 3 12ax7s and 3 7247s. The 7247 is an equivalent to a 12dw7: one triode is a 12ax7 and the other is a 12au7. My question is, am I able to use the 7247 in the phase inverter, or will this unbalance the circuit too much, or else damage the tube or amp? I did some research after I discovered my mistake, and from the looks of it I definitely won't want to use it in the gain stages, but I'm still unsure about the PI. Thanks in advance for your help.

Next time I'll pay more attention to the details.
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#2
It won't damage anything, but I wouldn't use it in the phase inverter.
I don't see why you wouldn't at least try it in a gain stage. A 12AU7 is a rather drastic drop in gain but it can be useful.
#3
It probably won't blow up but it won't be very good. As Colin said that is a drastic difference in gain between triodes. Half of your cycle will be stunted. It will cause substantial distortion. I'd be very surprised if it was pleasing distortion.

It would depend on what amp you have too. Some Fenders for example, use a single triode for the phase inverter. In that case it would probably work ok. To determine which triode was actually acting as the PI in that case would require consulting the schematic.
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Last edited by Cathbard at Mar 21, 2012,
#4
Ok thanks guys.

As I said, I ended up with these because of an oversight on the item description, so I'm just seeing if I can find a use for them so I won't waste the money. Thanks again!
Ibanez UV777 - Carvin TL60 & 727 - Jackson KE3
Splawn QuickRod - Mesa Stiletto & RoadKing - Peavey Ultra+ - Peavey Bandit
Some pedlulz & cabz


7 String Legion