Preamp Gain

[Mooly]

Mooly, my concern was not the transistor stability but the fact that the base junction of the input device is dc-biassed from the power rail with a simple pair of resistors and usually I see that most designers like not to have that without some decoupling because any noise on the rail is coupled to the base of the input device - you can get feedback via the rail - am I wrong in this case though ??

No, you are not wrong I was, maybe incorrectly, assuming clean supplies and correct implementation as a given.

If we say the current draw is around 10ma for a stereo pair then a 330 to 470 ohm resistor in series with the supply together with a 470 to 1000uF cap would give a clean rail.

 

[antonzp]

IMHO

 

[tnvijay]

No, but I do have the full board layout its lifted from. You would have to add R1 and C1 to the design. Or you could build the full version with tone controls.

Can anyone help me with a layout ready to do toner transfer? I am much interested in this Radford pre.. I have used the first stage line stage on a perfboard, and I am very impressed with the sonics.. I would like to build a complete board along with tone controls.. Also, let me know if a capacitor multiplier supply ( Juma cap multiplier) is suitable for the power supply section? I am a novice in diyaudio,but have done a few toner transfers and built a few.TIA

 

[Mooly]

The only board layout I have is that given in the service manual and which I posted a snip from back in an early post.

A cap multiplier type supply should be perfect for something like this so long as the voltage is stable (regulated).