Hachidori Fukami Tape/Phono Preamplifier

[JohnP]

It is not a good practice to blindly try different settings. There is good logic to selecting the starting point, which is making sure the FR goes to at least 20-24KHz. The proper resistance is calculated based on the head's inductance. I see that head's inductance listed at 700mH, in which case 55K is too low resistance - you only get about 12.5 KHz band. 125K should be more appropriate.

Sorry, the Nortronics head I’m using is a 9207. It has a listed inductance of 200mH at 1Khz.

 

[JohnP]

It is not a good practice to blindly try different settings. There is good logic to selecting the starting point, which is making sure the FR goes to at least 20-24KHz. The proper resistance is calculated based on the head's inductance. I see that head's inductance listed at 700mH, in which case 55K is too low resistance - you only get about 12.5 KHz band. 125K should be more appropriate.

What formula do you use?

 

[adrianywu]

He mentioned a 600ohm cable driver, but was a bit evasive about it. It is really not hard to properly load the input if you know the head inductance and cable capacitance. But to make it “idiot proof” for any user will require some ingenuity. At this price, he can tailor the preamp to each customer’s machine. Making a “universal” input might not be optimal.

 

[adrianywu]

J

What formula do you use?

use the standard tank circuit equation f= 1/2pi*Sq root(LC) Resistance will change the Q of the peak.