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View Full Version : Hammond 125C for SE use?

gmoon
03-08-2008, 05:35 PM
A little background: I'm currently designing a small amp, power stage is two 6DG6GT's in a parallel SE configuration. My PT (after rectification, filtering) should provide ~170 -180V, about 7 watts of audio power. I'm anticipating a load resistance in the 1500-1800 ohm range.

I'm having a tough time finding a SE OT in that range--most are 2500 ohms or above.

The Hammond 125C (8W) definitely fits my needs. With a 4 ohm speaker, 1500 ohms is a spec'ed setting. Several references: Angela.com, london power, the Hammond catalog, etc. indicate this iron works as both SE and PP.

But the Hammond website that references it's own catalog pages indicates I should look elsewhere for an SE transformer. I suppose I could punt and change the design to PP....
gmoon
03-09-2008, 02:36 PM
To restate the question:

Has anyone used any of "universal" Hammonds: 125C, 125D, 125E as single-ended OTs?
Chuck_Farlee
03-09-2008, 04:39 PM
It used to be that Hammond advertised the 125A-125E series as universal push pull and single ended replacements. This is before they started selling the 125ASE-125GSE which are true single ended output transformers. The 125A-125E OTs are really push pull transformers. After the SE series came out, Hammond dropped SE use from the 125A-125E series.

I've used the 125E in several champ builds and it works okay, but the 125ESE sounds much better.

I would use the 125E if you wanted to try your circuit, it can tolerate more DC in the core.

chuck
gmoon
03-09-2008, 10:23 PM
I've used the 125E in several champ builds and it works okay, but the 125ESE sounds much better.

I would use the 125E if you wanted to try your circuit, it can tolerate more DC in the core.
Thanks, Chuck

Could a 125ESE be used in a 1250 ohm mode? It's unspec'd, but if you follow the connection diagram, it looks as though Black & White would == 1250 ohms with a 4 ohm speaker.

Not spot on, but close. Since the 125ESE is good to 15 watts, 1/2 that wattage as an outa spec load might work?

Taking a second look at the load resistance graph, it doesn't seem at all terrible running one @ 5000 ohms, so 2500 for two might work just fine.... (two 6DG6GT's, that is.)