Audio Asylum Thread Printer
Get a view of an entire thread on one page
|For Sale Ads|
In Reply to: RE: Are these military potted trannys? posted by DAK on March 09, 2017 at 08:45:49
I was overly optimistic in thinking KT88s. The 6L6GC/KT66 suggestion is excellent, given the near perfect fit of Edcor's CXSE25-3.75K O/P "iron". ;>)
Add Tubelab's PowerDrive, for a positive g1 regime (Class "A2"), and the capability of the suggested O/P trafo will be utilized. Some magnetic headroom has to be reserved for GNFB, as unassisted UL mode is unlikely to exhibit an adequate damping factor.
I double checked the GZ34/5AR4 data sheet. The type is OK fed by 500-0-500 working into a choke I/P filter. :>)
So, avoid the large 5R4 forward drop and use a 5AR4 to rectify the "tall" B+ rail.
A 5V4, 6106, or 6087/5Y3WGTB is quite adequate to rectify the "short" B+ rail.
Thanks for the great suggestions Eli. I had been assuming SE, as PP requires 2x the tubes and around 2x the current. I really appreciate you researching the OP tubes and rectifiers. I used the Edcor CSXE series on another amp, but I believe a lower impedance.
The transformer is indeed potted, chokes as well. It has a "Spec" number (14513) but I don't know if they are military or not. They are black, and the PT weighs 14 lbs, 6 oz. I didn't mention before that the 5v filament windings are each rated for 3A. One of the 6.3v windings is rated at 2A and the other 2.5A.
Still quite a few options out there, but hard to anticipate what the PS would do near its limits.
The KT66 draws 1.3 A. of heater current, while the 6L6GC draws 900 mA. of heater current. Also, the 6L6GC can safely dissipate a bit more power.
Seems like the 6L6GC is the O/P tube to use. Jim McShane shows a "reissue" black plate TungSol 6L6GC-STR for $21.50/tube. Yum!
With some 'A2 action, 12 WPC is not an unreasonable target.
Post a Followup:
Post a Message!
This post is made possible by the generous support of people like you and our sponsors: