Hello everyone.
Silly question. Is it possible to place a potentiometer instead of resistors and switch to load mm cartridges in the phono preamplifier?
Silly question. Is it possible to place a potentiometer instead of resistors and switch to load mm cartridges in the phono preamplifier?
You can certainly do that, but the sliding contact of the pot may introduce noise in a circuit that has that much voltage amplification. Try it and see how it works out. Be sure to use a linear taper pot. If the pot has a metal case, be sure to ground that to avoid noise pickup.
Yes. I came up with this to see the difference of different loads on the sound, as it can be done while the record is playing. I have acquired a Grade Prestige Green p mount. It's on a Technics SL-10.
Charged with 47k without capacitor. Just the capacitance of the cable.
According to the manufacturer it can be loaded from 10k to 47k.
Charged with 47k without capacitor. Just the capacitance of the cable.
According to the manufacturer it can be loaded from 10k to 47k.
It's good to experiment with the pot to quickly home in on an optimum value. Measure the pot's resistance after finding the best setting and replace with fixed R for best noise performance. Plus, you won't accidentally bump the fixed resistor to a different value the way you might with a pot.
To avoid noise you can use a trimmer pot parallel with a fixed resistor inside the chassis or on the circuit board. Not as convenient as a knob at the front panel. Once dialed in, you can leave it alone.
A good solution is the use a 6 position switch to select different values; maybe 12 position. Two way
The double pot must be good quality, 50 kohm as minimu
But with 100k, 68k, 47k, 33k,22k, 15 k (or 10k) you will have a good range.
The switch is in parallel to input so there isn't anything to be worried.
Walter
The double pot must be good quality, 50 kohm as minimu
But with 100k, 68k, 47k, 33k,22k, 15 k (or 10k) you will have a good range.
The switch is in parallel to input so there isn't anything to be worried.
Walter
When the resistance goes as low as 10k 15k you significantly reduce the high frequency output of the cartridge. Probably best to pick a reasonable range of values, say 35k to 75k
Attachments
I can be agree.
But your is a simualtion and, as usual, it is a virtual world, there are also mechanical aspect that is not possible to simulate and each MM is different from others.
We can use the simulation only for a general discussion
The reason to go low is also when you use a step up for MC connected to MM.
In case in attach a old graphics done at Audioreview ( where I have a coolaboration) around frequency response of a MM on different load.
In addition a step up I am building with 3 ratios (10,20,40) and a 24 position switch that put in parallel on secondary differetn values to macth the Zsource od a MC
Walter
