...but you don't need years for a powered version.
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VLF MD with digital signal processing : Bee-Buzz 1
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Source: https://www.hifisonix.com/articles/r...e-mc-head-amp/
head amp = audio amp 20Hz to 20KHz = That's why they are using large capacitors
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Originally posted by Olly View PostIf you want an exact description of how the circuit works then do a search for "Marshall Leach moving coil preamplifier". Richard Lee adapted the circuit slightly but there should be a link somewhere to Leach's original circuit description...
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Oh man!,
I'm really tired. Get the spice simulation file in the previous post and make the simulations. If you don't have LTspice, download it and install into your computer. And run the fkn simulation.
This piece of circuit is really a KISS masterpiece. Thanks to Richard Lee and others making this possible.
The power consumption is not more than 11 to 12 mA at 6 Volt battery voltage. A short circuit would suck the battery to death. This is not the case. Why battery? No additional noise sources.
It's a moving coil (MC) pre-amp. What do you think what we are doing? We are moving the coil above the ground.
Aziz
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Originally posted by pito View Post
Parallel to battery there are 2 capacitors 100uF in series = 50uF for 10kHz that will be less than 1 ohm shorting AC signal
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Originally posted by Olly View PostI believe that the original idea behind the floating battery was to eliminate any possibility of DC current through the cartridge coil..
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Originally posted by moodz View Post
...though the original write up says the design is dependant on the source DC resistance of the coil pickup....affects gain.
In my modification there is an input protection diodes (charging the capacitors in high voltage pulses seen by the RX coil) and load balancing/discharging of the capacitors to ground.
It isn't a good solution. But it is really very tricky and simple. The signals are riding (floating) at the battery connectors.
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Originally posted by moodz View Post...so now we just wait for Aziz to finish building it.
Then comparing to the other pre-amps (it will have high input impedance, so not loading the RX coil).
I will test 3 different pre-amps. Maybe a simple NE5534 pre-amp too.
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Originally posted by Olly View PostT coil resistance.
The highest magnitude of current that may appear across the test probes on the board which is being tested will be 200 pA, which looks too modest to cause any sort of issues to the PCB under test. The test result indication is through a LED.
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