Beginner, simple circuit question

[Gold]

Weirdly enough, head 112 was the preferred one by some cutting experts that used them.

I thought the graph was of drive coils with no feedback.  If the graph is with feedback then head  112  has the flattest frequency response.

You are concerned with flat frequency response. Any impedance difference shouldn’t affect much.

Head 112 needs more damping at 20K. You need to tune the EQ networks to damp all the resonances for flat frequency response.

 

[barbaroja]

I thought the graph was of drive coils with no feedback.  If the graph is with feedback then head  112  has the flattest frequency response.

You are concerned with flat frequency response. Any impedance difference shouldn’t affect much.

Head 112 needs more damping at 20K. You need to tune the EQ networks to damp all the resonances for flat frequency response.

Graphs are of coils tested without feedback. I am trying to understand the intricacies and micro details. At some point I want to be able to rewind coils. Finding flat anodized aluminum cable 0.018mm thick has been difficult at best. And that is just one part of the equation.

 

[gridcurrent]

the earlier 3D and 3DII have 10 ohms (nominal) drive coils.
the 3DIIa has low Z coils.
among other benefits, the network designed for the "a" offers a measure of stability for the RA-1702 amplifier which is rated for 8 ohm and above loads.

 

[barbaroja]

the earlier 3D and 3DII have 10 ohms (nominal) drive coils.
the 3DIIa has low Z coils.
among other benefits, the network designed for the "a" offers a measure of stability for the RA-1702 amplifier which is rated for 8 ohm and above loads.

I have 4 heads. All of them are 3D II A. Maybe over the years that were reworked to different standards.

 

[barbaroja]

This from an old patent:

Thus, a drive coil in accordance with the pres
ent invention has a D.C. impedance of approximately
3 ohms and an inductance of approximately 90 uhy. As
the frequency increases, the inductive reactance of the
coil increases, and the current phase of the signal shifts
negatively. However, the RC circuit connected in series
with the drive coil enables a substantially constant im
pedance to be imposed on the output of power ampli
fier 76. Thus, the resistor 78 which may have a magni
tude of 4 ohms is shunted by a 5 ufd capacitor. As the
frequency of the signal on the output of power ampli
fier 76 increases, the impedance of capacitor 80 de
creases, thereby shunting resistor 79. In addition, the
current phase shift across capacitor 80 is a positive
phase shift' so that the output of power amplifier 76 re
mains substantially constant over the entire frequency
range of signals from the amplifier with a substantially
constant phase shift on the output terminals.


Any comments?