Running an input transformer backwards for output

K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

I am intrigued with the idea of using an amorphous core input transformer like the LL1676, but wired backwards (for either 2:1 or 4:1 step-down), as a parafeed, preamp output transformer. The parafeed cap would protect the delicate input trans from any DC.

It is my understanding that in parafeed, the primary coil of the output trans (actually what would normally serve as the secondary, since it is wired backwards) would be in parallel with the plate choke or CCS load. Therefore the effective load on the plate would be the parallel combination of both loads.

Here are my questions:

1) Is the effective load contributed by the transformer a fixed number (like Henrys), or is it a calculated result based on the input impedance of the next component in the system and the step ratio of the transformer?

2) Could such an arrangement be used to split phase? Could the two output wires on the transformer be connected to a balanced interconnect and feed a balanced circuit downstream? In a parafeed circuit, don't both sides of the transformer need a grounded leg?

3) I know Kevin and others have used the LL1676 with success. Are there other Lundahl transformers that seem particularly well suited for this purpose? I will likely be trying several DHT tubes (#26, 10Y, 71-A, 2P29L), although I may also play with more conventional fare. These cover a wide variety of Rp, but generally have a low Mu of 9 or less. I would need to know the max signal allowed on whichever transformer I buy (on both the primary and secondary coils).

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

Topic - Running an input transformer backwards for output - Prospect 14:22:07 02/08/19 (5)

RE: Running an input transformer backwards for output - Dave Davenport 09:44:18 02/09/19 (4)

RE: Running an input transformer backwards for output - Prospect 12:32:25 02/09/19 (3)

RE: Running an input transformer backwards for output - KevinC 07:36:19 04/05/19 (0)

RE: Running an input transformer backwards for output - Dave Davenport 13:55:05 02/09/19 (1)

I may have found the answer: It's a reflected load - Prospect 08:59:35 02/11/19 (0)

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.