Very neat looking build.
On the MC preamp, isn't the 240R (R307,407) in series with the input introducing a heavy noise penalty? Given the LT1028 is stated in its DS as being lower noise than a 50R resistor.
On the MC preamp, isn't the 240R (R307,407) in series with the input introducing a heavy noise penalty? Given the LT1028 is stated in its DS as being lower noise than a 50R resistor.
While you're reducing resistances, R309/409 at 100R are also introducing more noise than the LT1028.
I use LT3045 and LT3094 ultra-low noise stabilized power IC for MC amplification power supply. Next time, I will gradually transmit the circuit diagrams of each part
I use 50 ohms for R307, R309, and 510 ohms for R310. The noise is significantly reduced, but it is still slightly larger than LM497 10. Tomorrow I will use the LT1028 of the newly purchased fidelity product to try again
The following is the circuit diagram of my MC's first stage 10X amplification. I have several questions to ask you:
1. The R307 is used to burn the MC cartridge when the circuit is powered on or the device is in fault. The R307 is used too much to increase the noise, but it may not protect the MC cartridge when it is used too small. How big is the R307? I now use 50 ohms;
2. Whether 47K for R308 is too large for MC cartridge, and whether 1K should be used as the value of R310;
3. Whether C302 capacitance is necessary for MC cartridge and how large the capacitance value is.
Thank you!
1. The R307 is used to burn the MC cartridge when the circuit is powered on or the device is in fault. The R307 is used too much to increase the noise, but it may not protect the MC cartridge when it is used too small. How big is the R307? I now use 50 ohms;
2. Whether 47K for R308 is too large for MC cartridge, and whether 1K should be used as the value of R310;
3. Whether C302 capacitance is necessary for MC cartridge and how large the capacitance value is.
Thank you!
Those parts of the schematic following the Hitachi chip don't look too optimal noise-wise. I wonder why use AD797 with its relatively high current noise when the source impedance is of the order of 25k (50k pot) ? Surely a FET (OPA1641) would be a far better choice?
I have used many operational amplifiers at this level. Because it is the last level, I don't pay much attention to the noise performance. The main thing is to listen to whether I like the tone. Your reminder is reasonable. I will compare it with the FET operational amplifier.
I agree that ultimately the subjective sound is what matters. However noise does affect the subjective tonality. Too much LF noise for example will reduce the perceived ambience and give a 'thin' sound.
I used several kinds of LT1028. The voice tone is different, and some of them are noisy. It is difficult to judge whether the high-quality operational amplifier is true or false. I tried the discrete component operational amplifier. I bought a discrete component A single operational amplifier directly from the manufacturer in the Chinese market. This will not be false. This discrete operational amplifier has more details, and its noise is slightly larger than the LT1208 recycled in the Chinese market. Finally, I used the recycled LT1208 for the 10-fold amplification of MC level, The last stage uses a class A operational amplifier with discrete components, with balanced sound and minimum noise. I made the second board. The decoupling capacitors are all NIPPON AWJ top audio capacitors, which is the best sound quality I can tune.
Yes, my MC previous amplification factor is not accurate 10X, mainly for the convenience of selecting components. A little error will have no effect. Thank you for your attention!