Hi TJ: A couple thoughts. Its late at night here or is it early in the morning?
With guitar amps one of the reasons for the switch is to change tone/sound of the amp too isn't it? I think i remember it, at least in some guitar amps, being called crunchy and/or dirty which is actually sought out by some players for certain kinds of music. Distortion in the circuit is actually considered a good thing. Anyway, to my knowledge the 12AT7 has lower plate resistance and higher transconductance than the 12AX7. I took a quick look at on-line tube data and they are not mentioned as substitutes on the couple sites I visited. You can look here for the plate curves of two makes of the two tubes. They are quite different.
plate curves click on the left hand column to find the the info for the 12AX7.
In any event, I think you would be changing most of the operating points and likely the sound of your pre in order to change the gain for one source. This might cause more trouble than it solves.
Do you like the sound of the pre now?
Is the gain about right for your vinyl now? If you decrease the pres overall gain will it still be ok? (You generally want as little gain as possible and still be adequate)
I do not know anything about your pre. If you like the sound of it now and the gain in your phono is about right I would maybe attack the gain problem for the cdp alone instead of introducing all sorts of unnecessary changes to the entire system.
My guess is that the most direct way to solve a gain problem with a cdp would be to add some resistance in that individual circuit. Maybe as simple as adding a resistance to the interconnect or the OP stage of the cdp. You can install different pads (a pad is just a pair of resistors) on each input jack if you have sources of different sensitivity. Usually simple and inexpensive. Any local DIYer or guitar amp repair place can do it or you. (Depending on the circuit there is a little art in how best to do this because you dont want the added resistance to combine with capacitance/reactance and create a filter.)
You might check over at the Audio Asylum forums and see if someone has experience with your pres circuit. I cant tell you what size resistors to use w/o more info and even with more I might still be, well....clueless. Or call the manufacturer and explain the problem. This must be a common problem because the output of phonos and cdps is so wide these days. For most cdps these days lots of people choose passive or nothing at all.
I remain,
With guitar amps one of the reasons for the switch is to change tone/sound of the amp too isn't it? I think i remember it, at least in some guitar amps, being called crunchy and/or dirty which is actually sought out by some players for certain kinds of music. Distortion in the circuit is actually considered a good thing. Anyway, to my knowledge the 12AT7 has lower plate resistance and higher transconductance than the 12AX7. I took a quick look at on-line tube data and they are not mentioned as substitutes on the couple sites I visited. You can look here for the plate curves of two makes of the two tubes. They are quite different.
plate curves click on the left hand column to find the the info for the 12AX7.
In any event, I think you would be changing most of the operating points and likely the sound of your pre in order to change the gain for one source. This might cause more trouble than it solves.
Do you like the sound of the pre now?
Is the gain about right for your vinyl now? If you decrease the pres overall gain will it still be ok? (You generally want as little gain as possible and still be adequate)
I do not know anything about your pre. If you like the sound of it now and the gain in your phono is about right I would maybe attack the gain problem for the cdp alone instead of introducing all sorts of unnecessary changes to the entire system.
My guess is that the most direct way to solve a gain problem with a cdp would be to add some resistance in that individual circuit. Maybe as simple as adding a resistance to the interconnect or the OP stage of the cdp. You can install different pads (a pad is just a pair of resistors) on each input jack if you have sources of different sensitivity. Usually simple and inexpensive. Any local DIYer or guitar amp repair place can do it or you. (Depending on the circuit there is a little art in how best to do this because you dont want the added resistance to combine with capacitance/reactance and create a filter.)
You might check over at the Audio Asylum forums and see if someone has experience with your pres circuit. I cant tell you what size resistors to use w/o more info and even with more I might still be, well....clueless. Or call the manufacturer and explain the problem. This must be a common problem because the output of phonos and cdps is so wide these days. For most cdps these days lots of people choose passive or nothing at all.
I remain,