• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Info on IIT interstage trafos?

Used for A2 drive

IITC is a technique developed by Nobu Shishido to allow A2 drive of transmitting tubes. These transformers are hooked up in the opposite sense to conventional ITs with the secondary inverted in relation to the primary. They are designed to be used with transmitting tubes where the grid is biased positively with respect to the cathode the resulting grid current in the secondary cancels some of the DC in the primary allowing for a smaller transformer.

If you hook up a conventional transformer with the primary reversed with respect to the secondary, the transformer performance will likely suffer greatly, so these transformers are wound specially to allow this. These design also normally use a step down to get better drive.

I've just completed my take on the Shishido 801A amp using the special Tango inter-stage transformers (#10672) and the results are excellent. The design also uses cathode feedback from the OPT secondary to reduce the output impedance. A2 can work very, very well, but is more difficult to get right. Shishido's solution is very elegant.

Cheers/
Pete
 

jlsem

Member
2003-06-17 1:12 am
Dallas,TX
If you hook up a conventional transformer with the primary reversed with respect to the secondary, the transformer performance will likely suffer greatly, so these transformers are wound specially to allow this. These design also normally use a step down to get better drive.

Lundahl interstages are flexible enough to be successfully wired as step down transformers. The ones gapped for 5ma primary imbalance should be about right. The hard part about building a Shishido type A2 amplifier is finding the output transformers with a separate cathode feedback winding of the correct ratio. I don't know if custom wound OPT's are still available from the new Tango company.

John