PT Two primary windings vs one for 120V?

General discussion area for tube amps.

Moderators: pompeiisneaks, Colossal

Post Reply
User avatar
David Root
Posts: 3540
Joined: Fri Aug 04, 2006 3:00 pm
Location: Chilliwack BC

PT Two primary windings vs one for 120V?

Post by David Root »

Some 120/240 PTs use two identical primary windings which you connect in parallel for 120V and in series for 240V. Instead of the tapped single winding arrangement.

Is there any potential benefit to buying the two winding PT vs. the standard 120V only PT?

I am trying to remember but somewhere I seem to recall someone saying using the 120/240 two winding primary in parallel for 120V is better than the standard single winding 120V primary.
User avatar
Phil_S
Posts: 6048
Joined: Tue Oct 23, 2007 10:12 pm
Location: Baltimore, MD

Re: PT Two primary windings vs one for 120V?

Post by Phil_S »

If you parallel two windings for 120V, you get 2x the primary VA rating. When you put them in series for 240V you get the same VA rating as the paralleled windings.
User avatar
David Root
Posts: 3540
Joined: Fri Aug 04, 2006 3:00 pm
Location: Chilliwack BC

Re: PT Two primary windings vs one for 120V?

Post by David Root »

OK, that makes sense.

So if there are two versions of the primary available, the single 120V only and the 120/240 arrangement, both versions with the same secondary ratings, and both versions have the same dimensions and weights, then there should be no advantage to buying the 120/240 version for 120V only use?

If that's true I can save $5.00!
Post Reply