EE21, EE23 Multi Purpose Board V6.5
EE21 or EE23 Board
Lundahl used two internal wire schemes Lundahl uses for this transformer family. This is the reason why we have two boards, EE21 and EE23, and each transformer type can only be used with one of the two boards. For the end user, optics and use is the same. Basically LL1588, LL1592, LL1684, LL1690, LL1948 use Board EE23, all other transformers use EE21.
Below is pictured Board EE2, but .voard EE23 looks optically identical. When ordering we ship automatically the right board (EE21 or EE23) with the transformers.
Finally, no more glueing transformers inside the amplifier, and no more hand wiring!
After designing these two small PCBs, I was surprized how many transformers can be used with it.
Gain, Attenuation, Phase splitting, Phase reversal, balanced to unbalanced or vice versa, using a termination network, use an external gain switch.... ALL if this is possible.
Please do not try to understand all applications at the same time, and all connections and things that have to do with it. Simply read only what applies for intended application, and then for the transformer of your choice, and connect it with the advised connection schema. Like this the right choice is made very quick, and you can't go wrong when building it.
The EE21, EE23 boards already work before having to worry about much about connections, and termination comes afterwards anyway. As a minimum only the gain has to be set with the jumpers J1, J2, J3. (Or use for this external switch board instead). Simply use the Connection Schemes overview (see contents above here) and it works.
Moving Coil. The board is made to work simple, and yet can do many options which you may want to play with later.
Output Applications. These are typically tube parafeed applications, apart from LL5402 which is very low impedance, and intended to drive it with transistors or an IC. Choose the gain, connect input and output, and the board works.
Each transformer allows two gain factors, and with some applications, the boars can be used reversed. The two gain factors can be chosen fixed with solder jumpers, or variable using the External switch board EE22. This board may also be added later.
Set Gain with Solder Jumpers
at the back side.
Or, Set Gain with External Switch
with J1, J2, J3,
Open Jumpers J1, J2, J3, and use the Switch
After choosing the gain (High or Low), the board already works!