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Post by tgftele on Oct 23, 2016 15:57:59 GMT -7
Hi All,
I have a new/used Carmen Ghia and have loved the 12AY7EH in V2 (PI) Position. However, my question is, is this problematic for power tubes? I tried a set of Tung Sol EL84s at practice Friday, and they failed. Immediately replaced them with known good JJs and did not have any issues the last hour. Thoughts or advice? Thanks!!
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Post by John on Oct 23, 2016 16:55:35 GMT -7
I wouldn't think an ay7 would be the best match. I don't know the technical differences, but there was discussion years ago about ax7...at7...and ay7 tubes. If I remember, some don't handle tone very well. ...and they were better suited for driving reverb tanks and such.
I would stick with a ax7 or a 5751.
And I wouldn't blame power tube failure on a pi tube. With the current level of quality, sometimes they just go bad..
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Post by BritInvasion on Oct 24, 2016 9:36:38 GMT -7
I agree with John. a 12AY7 has much lower gain and passes more current than a 12AX7 but it wouldn't damage the output tubes.Probably just a bad set.
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Post by tgftele on Oct 24, 2016 13:27:42 GMT -7
Hey thanks, much appreciated! Unfortunately the only other tubes that have actually failed me mid-song we also Tung Sol...6V6s...so I am quickly and happily back to JJs for all power sections. I will continue keeping a spare set of EL84s in the gig tool box, lol. The amp is absolutely great though, with just about any PI tube I have tried, 5751 (stock), 12AX7 (a bit more grit as expected), 12AY7 (cleaner/smoother, more defined low end), 12AU7 (very similar to the 12AY7), all different but all sound good in their own way.
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Post by sharkboy on Oct 25, 2016 20:06:44 GMT -7
It really shouldn't make much difference in a PI. It would provide a hair less amplification of the signal, but more current. FYI: most PI circuits don't actually boost the signal.
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Post by premiumplus (Dave) on Oct 28, 2016 7:11:50 GMT -7
I think John's referring to the article that Myles Rose wrote about preamp tubes some years ago. In it he said that the 12AT7 is not that great for a first stage tube where your basic tone is established, and that it is more suited to drive reverb transformers.
The phase inverter does work a tube harder than the first gain stages do, and I think Myles suggested that you replace your PI every other output tube change.
As to the original question, I've run a 12AY7 in P2 of the Ghia, and it worked ok; it's a matter of taste here. It won't hurt anything as far as ruining output tubes...I think that was a coincidence.
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