what is the phase inverter pot for?
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Re: what is the phase inverter pot for?
A very hot topic at some other amp forums as well.
directions for setting it at C-tone forum.
Now back to the other pot,
directions for setting it at C-tone forum.
Now back to the other pot,
Re: what is the phase inverter pot for?
I guess what I am trying to ask is not so much HOW to adjust it, but rather, what does this adjustment do to the sound/feel of the amp?
Re: what is the phase inverter pot for?
I really wasn't trying to be difficult when I referred you to the other thread. What you're after is in there in greater detail than this, but the short of it is that the amp should feel more muscular, and have easier feedback and greater bloom when you have the right PI tube and the right adjustment made.pula58 wrote:I guess what I am trying to ask is not so much HOW to adjust it, but rather, what does this adjustment do to the sound/feel of the amp?
-g
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David Root
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Re: what is the phase inverter pot for?
Yes. It's used to adjust DC imbalance in the PI so that the inverted and non-inverted AC signals to the push-pull power tube pair are balanced ie the same voltage.
You need a signal generator to do this if you want to see the AC balance point. Use 400Hz and 1KHz, you may see a slight difference in the AC balance points at the two frequencies.
Then you fine tune it with your ear by moving the pot so that you get the best ie greatest amount of harmonics when you lightly hit the strings with the volume up. You need to wait a few seconds after you make a pot change so that the caps settle.
AC measurements should really be done on the OT secondary as that takes into account power tube and OT imbalances, BUT your ear is the final arbiter.
I find it very difficult to do all this with a 5K pot. 10K works much better. If you have a very well balanced pair of triodes in your PI tube there will not be much difference between the AC and DC balance points, and a 5K pot should work. But use a 10K anyway, it's easier, especially if you don't have a tone generator and are doing it solely by ear.
What greiswig says, is "it". If you don't get that, try a different PI tube.
You need a signal generator to do this if you want to see the AC balance point. Use 400Hz and 1KHz, you may see a slight difference in the AC balance points at the two frequencies.
Then you fine tune it with your ear by moving the pot so that you get the best ie greatest amount of harmonics when you lightly hit the strings with the volume up. You need to wait a few seconds after you make a pot change so that the caps settle.
AC measurements should really be done on the OT secondary as that takes into account power tube and OT imbalances, BUT your ear is the final arbiter.
I find it very difficult to do all this with a 5K pot. 10K works much better. If you have a very well balanced pair of triodes in your PI tube there will not be much difference between the AC and DC balance points, and a 5K pot should work. But use a 10K anyway, it's easier, especially if you don't have a tone generator and are doing it solely by ear.
What greiswig says, is "it". If you don't get that, try a different PI tube.