Thank you! I updated the schematic at once according to your values. Today I modified the PCB to accommodate 3 resistors to combine, instead of 2 in all TCs. I wish to be as precise as possible. But using 1% tolerance resistors, I'm afraid it will remain a good exercise. However, I usually buy a bunch of 10 and carry on a selection. I wish to stay with resistors whose value is as close as possible among them, and if I see I have to use too different values, I will accept a higher tolerance to the nominal value.
I tried to understand the grid stop topic, but I couldn't find anything new or useful, able to start my brain. Too often you meet people on the forums who don't know what they are speaking about. Some say the grid is like a coil, so the stopper is needed. Should I believe in that? It is needed with transistors too! I know it prevents oscillation due to parasitic C & L by lowering their Q. For sure the stopper does not have the main purpose of avoiding RF interferences, it is a plus. And perhaps the Miller effect should be considered too.
Having a pair of Acoustat 1+1 I preferred to stay on the conservative side, and always choose a high value. The truth is I have to work on the Acoustats.
Perhaps you are referring to the Johnson noise, because of MC's low impedance and the high gain needed? You are right, it is too high even with an MM. But LSK489's Cin is very low, and there is no Miller effect or so, because it is a cascode. Perhaps, due to LSK489's low transconductance, I can omit the stopper. I have some ferrite beads, but they are conductive and short the leads. Can I find nonconductive ones?
I think the Vera will not work with MCs, but it is worth a try.
Now I'm verifying the space among tracks on the PCB, where a high voltage difference is present. I found out that 1.25mm is enough for 200V. At first sight, it seems to me to be a value too small.
I tried to understand the grid stop topic, but I couldn't find anything new or useful, able to start my brain. Too often you meet people on the forums who don't know what they are speaking about. Some say the grid is like a coil, so the stopper is needed. Should I believe in that? It is needed with transistors too! I know it prevents oscillation due to parasitic C & L by lowering their Q. For sure the stopper does not have the main purpose of avoiding RF interferences, it is a plus. And perhaps the Miller effect should be considered too.
Having a pair of Acoustat 1+1 I preferred to stay on the conservative side, and always choose a high value. The truth is I have to work on the Acoustats.
Perhaps you are referring to the Johnson noise, because of MC's low impedance and the high gain needed? You are right, it is too high even with an MM. But LSK489's Cin is very low, and there is no Miller effect or so, because it is a cascode. Perhaps, due to LSK489's low transconductance, I can omit the stopper. I have some ferrite beads, but they are conductive and short the leads. Can I find nonconductive ones?
I think the Vera will not work with MCs, but it is worth a try.
Now I'm verifying the space among tracks on the PCB, where a high voltage difference is present. I found out that 1.25mm is enough for 200V. At first sight, it seems to me to be a value too small.
No, ferrites conduct electricity (but not as well as metals), make sure the neighbouring leads are insulated with some sleeving.
I accidentally put the wrong files in the .zip attached to post #8. A corrected .zip file is attached to this post. Rows 1...10 of the .xls file are for checking given RIAA correction network values, rows 12 and beyond for dimensioning a RIAA network.
My phono RIAA EQ "Vera" (see post #13) has a gain block made by a cascode/Sziklai gain stage followed by a buffer, to drive the EQ network in the best possible way. I don't like to get the signal from a collector/plate/drain. So it is not a simple "one transistor" block.
Vera's gain is kind of very high, nearly good to accept an MC. So the chain is gain>EQ>gain>EQ>buffer. Do you see anything wrong with it?
Vera's gain is kind of very high, nearly good to accept an MC. So the chain is gain>EQ>gain>EQ>buffer. Do you see anything wrong with it?
Doing all the gain as well as RIAA correction just in one block is rather tricky to get right.
In tube preamps it's not really practical or sometimes possible to have so much gain in one stage.
I also find in not really doable in a RIAA network with opamps. Although in that case I almost always use an active circuit instead.