|
Post by loucardguitar (Johnathan) on Apr 6, 2021 21:14:38 GMT -7
I was just curious if there was a consensus among the Z Talk crowd regarding when you should change the phase inverter (PI) tube. I know some people say that you should change the PI tube whenever you change the power tubes. Other's say that it's like any other pre-amp tube and should last quite some time. Since it's driving the power tubes, I'm sure it's used a little heavier than say your V1, but I'm not quite sure it would really be pushed necessarily as hard as the power tubes. FYI - I have a 2017 era Cure and I'm using NOS military spec (i.e. JAN) 12AT7's for the PI tube. I have built quite a stash of NOS and ANOS 12AT7's (9 mil spec and 5 others). Just asking to determine if I should keep hoarding or if I might be in good shape for quite some time. Ha!
|
|
|
Post by zpilot on Apr 6, 2021 21:39:35 GMT -7
My personal preference is to replace NOS 12AT7's every other power tube change. On amps with a 12AX7 PI I replace it every time I put in new power tubes and I always go with a Sovtek 12AX7LPS. 12AT7's are still relatively cheap and available or a least they were the last time I checked. PI tubes may last longer than this but since I have thousands of dollars invested in guitars, amps and pedals I just can't see the sense in scrimping there.
|
|
|
Post by loucardguitar (Johnathan) on Apr 7, 2021 8:49:15 GMT -7
My personal preference is to replace NOS 12AT7's every other power tube change. On amps with a 12AX7 PI I replace it every time I put in new power tubes and I always go with a Sovtek 12AX7LPS. 12AT7's are still relatively cheap and available or a least they were the last time I checked. PI tubes may last longer than this but since I have thousands of dollars invested in guitars, amps and pedals I just can't see the sense in scrimping there. Thanks. Yeah, that's kind of the direction I was thinking would be best. Maybe every other power tube change. Especially with NOS military spec tubes. If I were using modern tubes. No question. I would change every power tube change. And yeah, you can still get good 12AT7's for reasonable prices. Most of my JAN's I got from KCA. Back when they had the JAN Sylvania's for like 18-20 bucks a piece. I believe the high end range on NOS 12AT7's is in the $30's or so.
|
|
|
Post by zpilot on Apr 8, 2021 11:50:02 GMT -7
I keep those NOS 12AT7s that I pull because they still have a lot of good life in them. You never can tell what the supply is going to be like down the road. I might be able to use them as a reverb driver tube. I sell a few to customers for $5 when they are on a tight budget and their present PI is weak or they are wanting a repair just to sell the amp. I even keep the 12AX7LPS tubes for various purposes. That way it is not a total loss replacing those PI tubes as often as I do.
|
|
|
Post by Seńor Verde on Apr 9, 2021 6:48:48 GMT -7
For a couple years I changed PI tubes whenever changing power tubes. Then I tried swapping back and forth between a new PI and the one that was already in the amp and didn't notice a difference. I still do this and if there is a noticeable difference, I swap the PI tube.
|
|
|
Post by helmi on Apr 9, 2021 16:32:38 GMT -7
For a couple years I changed PI tubes whenever changing power tubes. Then I tried swapping back and forth between a new PI and the one that was already in the amp and didn't notice a difference. I still do this and if there is a noticeable difference, I swap the PI tube. I think you just might be smarter than the rest of us! good idea.
|
|
|
Post by Chilly Gibbons (Todd T.) on Apr 9, 2021 17:19:50 GMT -7
I occasionally run the PI through my tube tester to verify it’s health. Usually tests strong.
|
|
|
Post by Seńor Verde on Apr 10, 2021 17:07:39 GMT -7
For a couple years I changed PI tubes whenever changing power tubes. Then I tried swapping back and forth between a new PI and the one that was already in the amp and didn't notice a difference. I still do this and if there is a noticeable difference, I swap the PI tube. I think you just might be smarter than the rest of us! good idea. Probably not smarter, just tighter with my money.
|
|
|
Post by zpilot on Apr 11, 2021 1:39:02 GMT -7
That is why I try to recoup some of the cost by using the pulls elsewhere. It's not a total loss.
|
|