Hi
on nr. 400 of Audioreview magazine in Italy I have wrote an article about the OpAmp fono + mc stage.
The power supply is from battery.
I use the Opa2604, one for channel a passive Riaa exactly the same of my other stuff with all tubes.
The 2604 are powerd with +/- 24 volts, I made this choiche because it is one othe few stuff that can run at those voltage.
The MC stage works with 12 volt, using the 2SK364.
In attach the photo of proto ; it has 2+2 battery at 12 volts; two pcb for a test of the project + 2 little board with MC circuit.
There is also a circuit for charge and a little display to check the voltage.
The test on lab were fine.
In fig 1 there is a freq answer of MM
Fig. 2 is resp. on MC
3 is the THD vs freq on MM stage
The circuit is 4 for MM
for MC is 5
The max signal input in MM 1s 155 mV at 1 Khz; for MC is 6 mV
The sn is 76 dB on MM and same on MC, good.
The listening test from my friends are with a very good impressions.
Walter
on nr. 400 of Audioreview magazine in Italy I have wrote an article about the OpAmp fono + mc stage.
The power supply is from battery.
I use the Opa2604, one for channel a passive Riaa exactly the same of my other stuff with all tubes.
The 2604 are powerd with +/- 24 volts, I made this choiche because it is one othe few stuff that can run at those voltage.
The MC stage works with 12 volt, using the 2SK364.
In attach the photo of proto ; it has 2+2 battery at 12 volts; two pcb for a test of the project + 2 little board with MC circuit.
There is also a circuit for charge and a little display to check the voltage.
The test on lab were fine.
In fig 1 there is a freq answer of MM
Fig. 2 is resp. on MC
3 is the THD vs freq on MM stage
The circuit is 4 for MM
for MC is 5
The max signal input in MM 1s 155 mV at 1 Khz; for MC is 6 mV
The sn is 76 dB on MM and same on MC, good.
The listening test from my friends are with a very good impressions.
Walter
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Very interesting, and nice project.
I have a few small comments, I'd recommend moving those bypass caps to the boards, the wiring inductance negates some of their benefit.
I hope you have fuses in series with the batteries - if a cap or other component fails you can have a very spectacular fire.
I have a few small comments, I'd recommend moving those bypass caps to the boards, the wiring inductance negates some of their benefit.
I hope you have fuses in series with the batteries - if a cap or other component fails you can have a very spectacular fire.
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