I also measured wiring capacitance from input RCA to valve grid is 47pF.
When a manufacturer says optimal capacitance in parallel with the optimal resistance load is telling that I have to put allthe value recommended or have I to substract the sum of (65pF input capacitance of Itch+47pF input wire Itch+220pF Linn Ekos wire) total 330pF
400-500pf recommended - 330pF = 70-170pF?
When a manufacturer says optimal capacitance in parallel with the optimal resistance load is telling that I have to put allthe value recommended or have I to substract the sum of (65pF input capacitance of Itch+47pF input wire Itch+220pF Linn Ekos wire) total 330pF
400-500pf recommended - 330pF = 70-170pF?
(miller capacitance.. Not sure how accurate of a reading you'll get this way)
Your .pdf lists 1.1pF Cg/a (grid to plate i.e. transfer) and a V/V=100 (μ) for E283CC
This link 6N2P, 6N2PEV (6H2n, 6H2n-EB) lists 0.55pF (max 0.8pF) and 100 +/-15 gain (μ) for the 6N2PEV. In my experience they tend to the lower gain tolerance.
So with the Siemens you may have over 100pF Miller. Something like 115-120pF when adding Cg and base/layout parasitics. Then you should add what is in the wiring. There are low capacitance coax wires from manufacturers like Mogami, Belden, or some surplus Navy spec Teflon coated thin ones, or the Blue Jeans cable etc. So to cut some really significant pF number from the interconnecting and internal wiring contributions if needed.
This link 6N2P, 6N2PEV (6H2n, 6H2n-EB) lists 0.55pF (max 0.8pF) and 100 +/-15 gain (μ) for the 6N2PEV. In my experience they tend to the lower gain tolerance.
So with the Siemens you may have over 100pF Miller. Something like 115-120pF when adding Cg and base/layout parasitics. Then you should add what is in the wiring. There are low capacitance coax wires from manufacturers like Mogami, Belden, or some surplus Navy spec Teflon coated thin ones, or the Blue Jeans cable etc. So to cut some really significant pF number from the interconnecting and internal wiring contributions if needed.
Since the in each circuit gain and the tube base parasitics (significant for the multiplied pins one) vary a lot, the safest method is to compare bandwidth at the signal point before the RIAA elements grid as with the signal generator's Z versus a high series resistor value added to it and calculate back from that.
Using the vinylengine calculator https://www.vinylengine.com/cartridge_database_tools.php
the optimal value for load resistance is 35K9 and resonance 11.4kHz
the optimal value for load resistance is 35K9 and resonance 11.4kHz
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Provided you have a function generator, and a scope this is not too hard to do.
Disconnect the 47K load resistor at the input to your phono stage. Connect a function generator with 50 ohm output directly to the input - set the output voltage to around 100mVpp @ 100kHz sine wave. Make sure the function generator output is DC coupled. (Most are) Measure the AC signal voltage at the plate of first stage with your scope and make this your reference voltage. Insert a 100K 1% or better resistor in series with the generator output. Measure the output voltage at the plate of the first stage and call this Vmeas. Find the ratio of the two voltages, convert to dB and look for the closest value in my table.
(Vmeas/Vref)log x 20 and match to closest value in table. If you are careful you might get within 10% or so of the actual value. (If the scope will give you numerical voltage measurements so much the better.)
Disconnect the 47K load resistor at the input to your phono stage. Connect a function generator with 50 ohm output directly to the input - set the output voltage to around 100mVpp @ 100kHz sine wave. Make sure the function generator output is DC coupled. (Most are) Measure the AC signal voltage at the plate of first stage with your scope and make this your reference voltage. Insert a 100K 1% or better resistor in series with the generator output. Measure the output voltage at the plate of the first stage and call this Vmeas. Find the ratio of the two voltages, convert to dB and look for the closest value in my table.
(Vmeas/Vref)log x 20 and match to closest value in table. If you are careful you might get within 10% or so of the actual value. (If the scope will give you numerical voltage measurements so much the better.)
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That's a kind effort to calculate and provide a look up table Kevin. Will be a good rough guide to many. But some circuits or lab gear differ. Next thing Merlin may ask you for instance could be what if my function generator is 600 Ohm and on what node do I measure on my Itch build which is a mu follower?