Since 1993 Copyright Notice

EE21, EE23 Boards V7.1. All Connection Schemes

1. Overview
2. MC Applications
3. Input Applications
4. Output Applications
5. All Connection Schemes, Complete Overview
   (you are here)
6. Some unsorted Application Information

EE21 or EE23 Board?

Lundahl uses two different internal connection schemes for this transformer family. Basically one of the two secondary windings is reversed, that is all. But it does mean, a PCB made for the one transformer type, can not be used for the other. For this reason we have two boards, EE21 and EE23, so each transformer type can only be used with one of the two boards. Optically EE21 and EE23 look the same, and also connections to the outside world are the same. So the page with "All connections" applies for EE21 and EE23 as well. Only PCB tracks are different.

Transfer Ratio.

Some transformers are intended for gain, some for attenuation. For this reason we call this transfer ratio.

Close J2: Low transfer Ratio. (J1, J3 open)
Close J1+J3: High transfer Ratio. (J2 open)

Grounding

1) Use of the Ground (G) Connections

The G connections are connected to the board ground plane at both sides. They are used if an XLR cable needs to be shielded, or to send or receive an unbalanced signal.

• If L- (or H-) is is connected to G, the other end becomes an unbalanced connection. In the configuration pictures, there are many examples for this.
• If connecting L+ (or H+) to G, the other end becomes inverting.

2) Use of J4 and J6, with balanced output signal

A grounded center tap is ideal, to transmit signal over a XLR cable. This enforces a ground reference to the balanced signal, and yet it stays normally balanced.

• J4 grounds the center tap of the H-Side output signal. It can not used be used for an RCA Output.
• J6 grounds the center tap of the L-Side, in case the L-Side is used as output, AND if those windings are in series.
• J4 and J6 are not used together.

Several Input configurations		Several Output configurations
1			7
2			8
3			9
4			10
5			11
6			12
Several Input configurations		Several Output configurations