My name is Rupert Choi from Hong Kong. I also want to thank my friend T. M. Chan who told me about the Pass Labs web site and encouraged me to work on this DIY project. I did take a month to finish it as I need to work on it only after work and the total cost is around 400 USD.
I work on this project by following the principles that I. Put the volume control on the output end (I did choose to DIY ladder type volume controls which occupied half of the project working time and cost around one third of the total DIY costs.); II. Use 10dB gain (I put 432 ohms between the Mosfets and the effect is very good.); III. Use point to point soldering (The circuit is very simple and I constructed the circuit above a piece of half inch MDF.); IV. Build two separate mono blocks (transformer and power supply regulators are separated for both channels); V. Use balanced input and output to reduce the noise (the SE input and output were made for spare use only); and VI. Use higher regulated power supply voltage (I used 64V). I did follow the schematics from the Pass Labs except that the 221 resistor at the input was eliminated. Besides, I used a shunt regulator instead. The components that I used were those with good performance/price ratio. I used the locally made toroidal transformers, Sprague and Elna electrolytic capacitors, Solen MKP coupled with MIT RTX capacitors, and Vishay Dale and RS resistors. The circuits worked perfectly when I first hooked it up with my gear. The sound of this preamp is very good. The noise floor is very low. I turn the volume control to its maximum while without playing any CD, I cannot hear any noise from the speaker. The sound is very clear, transparent and dynamic. The soundstage is very deep and it is very airy, I can hear a lot of detail at the high frequency. As I have just used the machine to listen to CD for just 4 hours, I am sure that it will be much better after fully run in for a week. Best regards Rupert from Hong Kong
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