Pultec EQP-1A

[Quayhog]

I'm getting ready to build up a pair of Rainton's EQP-1a chassis.  I've managed to acquire all of the specialized parts with the exception of the HS-29 interstage transformer 20k-80k with its 1:2 ratio.  I have several possible choices I've acquired over the years but none have the 1:2 ratio of the original. 
Which would make the best substitution?

Langevin TF412B 20k-60k (1:1.82) estimate (no CT)
Triad HS-27 15k-60k (1:172),  NOS
UTC A-18 15k-80k (1:2.3),  NOS
Halldorson H4000 15k-60k (1:1:172)

These all have suitable frequency response, I'm not sure of db ratings.

 

[vari-mu]

  I think  Triad HS-27 15k-60k (1:1.72),  NOS  !!!

 

[Quayhog]

The HS-27  is my preferred choice too. Trouble is I only have one and I have a pair of chassis coming.  I'm thinking build one project with Triads and the second one with the UTC.  I have  UTC A-20 600:600, and a Triad HS-56.  The S-217d are Cinemag reproductions.

 

[Quayhog]

I need to disqualify the Halldorson and the Langevin. They are designed for single grid circuits.  They are otherwise nice transformers awaiting a project.

 

[AusTex64]

What inductor do you plan to use?

 

[mikeyB]

colin at audiomaintenance.com has the pultec clone parts made by carnhill

 

[Quayhog]

I used the inductor from vintage wings.com.  Seems top drawer.  I'm 2/3 throwing the builds.  I used Triads for on and UTC for the other.  The 600:600 are no issue.  I needed to use a Triad HS-27  (1:1.72 ratio) ant on the UTC one I used an A-18 (1:2.8 ratio).  I should know soon enough.

 

[salomonander]

I used the inductor from vintage wings.com.  Seems top drawer.  I'm 2/3 throwing the builds.  I used Triads for on and UTC for the other.  The 600:600 are no issue.  I needed to use a Triad HS-27  (1:1.72 ratio) ant on the UTC one I used an A-18 (1:2.8 ratio).  I should know soon enough.

id love to know how it worked out....

 

[AusTex64]

I used the inductor from vintage wings.com.  Seems top drawer.  I'm 2/3 throwing the builds.  I used Triads for on and UTC for the other.  The 600:600 are no issue.  I needed to use a Triad HS-27  (1:1.72 ratio) ant on the UTC one I used an A-18 (1:2.8 ratio).  I should know soon enough.

How does the HF look out to 50KHz with the HF boost on 16K, narrow band width and full boost? Do you see a significant HF rise starting about 22KHz extending out to 50KHz? That's what I got with the Vintage Windings inductor. Was able to get rid of the inductor ringing by using the Carnhill inductor and tuning the Zobel network on the interstage.