Hi
out of curiousity i bought two "Mofi 323 DIY kit's" to assemble a symetrical input to output phonostage.
The result is so far not bad, but output levels seem very low compared to other MC Phono Stages i use. I needed 7-9db more gain to be on similar levels. (atm. AT OC9 for testing)
Some investigation brought up that - in the original diagram from Naim - R13 220R can be reduced by half, lifting the gain +6dB
"Note that the gain can easily be adjusted (I've tried changing it by afactor 2 with no problem) by changing out R13 (220R). For example putting in a 110R in its place will double the gain,which may be useful if you are trying to match the subjective output from LP and line inputs" - Yes i want that, but:
Another person tried the opposite, decrease the gain, using a 470R resistor as R13, but he also changed C4 from 47uf to 22uf. This would indicate that in the increase +6db case, C4 should also be swapped to 100uf.
i then found an explanation, that C4, 47uf acts as rumble filter with the 220R in series and that increasing gain leads in higher (30Hz?) HP filter.
Now, lets say i wanted to reach 65dB of gain, and needed 10-12 db more, would 56R and 220uf be the right way, or is the circuit not designed to go that high?
How about input configuration for a DL103R - or even lower impedance MC like ZYX or certain Ortofon MC's?
original circuit:
Mofi clone circuit, here it's R58 & C19
thanks for hints. here is the PSU circuit:
this circuit seems to produce more 100Hz Hum then my lab PSU...
thats it so far.
cheers!
out of curiousity i bought two "Mofi 323 DIY kit's" to assemble a symetrical input to output phonostage.
The result is so far not bad, but output levels seem very low compared to other MC Phono Stages i use. I needed 7-9db more gain to be on similar levels. (atm. AT OC9 for testing)
Some investigation brought up that - in the original diagram from Naim - R13 220R can be reduced by half, lifting the gain +6dB
"Note that the gain can easily be adjusted (I've tried changing it by afactor 2 with no problem) by changing out R13 (220R). For example putting in a 110R in its place will double the gain,which may be useful if you are trying to match the subjective output from LP and line inputs" - Yes i want that, but:
Another person tried the opposite, decrease the gain, using a 470R resistor as R13, but he also changed C4 from 47uf to 22uf. This would indicate that in the increase +6db case, C4 should also be swapped to 100uf.
i then found an explanation, that C4, 47uf acts as rumble filter with the 220R in series and that increasing gain leads in higher (30Hz?) HP filter.
Now, lets say i wanted to reach 65dB of gain, and needed 10-12 db more, would 56R and 220uf be the right way, or is the circuit not designed to go that high?
How about input configuration for a DL103R - or even lower impedance MC like ZYX or certain Ortofon MC's?
original circuit:
Mofi clone circuit, here it's R58 & C19
thanks for hints. here is the PSU circuit:
this circuit seems to produce more 100Hz Hum then my lab PSU...
thats it so far.
cheers!