This stage is super quiet and sounds just fine. I may publish pictures and circuit diagram.
Hi Joachim,
Please do.
Also, have you tried using other transistors in the input of the Paradise? Like the low Rbb ROHM and such?
Cheers,
Mogens
Hi Mogens ! Yes, i tried other transistors. The good old japanese ( ROhm, Toshiba, Hitachi ) are more or less unobtanium. There are some interesting Zetex. I think we discussed this.
On the other hand there are 8 transistors parallel in the Paradise so noise is really close to the physical limit. Alo running each pair at ca. 2mA makes sure that the 1/F noise is not shifted up. More current brings even less voltage noise but there is a point where the 1/f noise shifts upwards. The optimum is ca. 10mA and that is aproximate the total current in the input stage. BC327-40 and BC337-40 also have high HFE. That reduces the input offset. On the other hand the Paradise has an input offset trim. I think it is good as it is.
On the other hand there are 8 transistors parallel in the Paradise so noise is really close to the physical limit. Alo running each pair at ca. 2mA makes sure that the 1/F noise is not shifted up. More current brings even less voltage noise but there is a point where the 1/f noise shifts upwards. The optimum is ca. 10mA and that is aproximate the total current in the input stage. BC327-40 and BC337-40 also have high HFE. That reduces the input offset. On the other hand the Paradise has an input offset trim. I think it is good as it is.
The good old japanese ( ROhm, Toshiba, Hitachi ) are more or less unobtanium.
Hi Joachim,
Yes, I know. I have only very few of the Toshiba Type. The Rohm Type I have a little more of. However, unfortunately most of the Rohm type I have are from different hfe group.
Thank you for the schematic for the alternative power supply. It actually is great as I have been thinking about building a Paradise RIAA as a present for a friend of mine. Could make the build a little easier.
Cheers,
Mogens
Pre regulator stuffed, transformers and resistors missing. Stuffed Paradise R3 stuffed, semiconductors missing. FdW shunt regs, unstuffed boards.