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Designing an Interstage Transformer

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Unfortunatly when I was attaching the bondout wires, I broke one secondary at the margin. It looks like I'll have to strip it and start over.

The good one is fully assembled and looks good with a signal generator (600R output) and 240R load.

I'll Perform some better measurements later.
 

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Unfortunatly when I was attaching the bondout wires, I broke one secondary at the margin. It looks like I'll have to strip it and start over.

Look up edcor. They sell both cores and bobbins at a really reasonable rate. It used to be you had to buy large quantities or salvage. If Edcor actually makes a go of the small scale sale of transformer parts things will get very cool for the small guy.... so support them!

dave
 
I've got EI-100s from Edcor, along with endbells. They didn't have bobbins at the time I ordered them.

That said, these are EI-85 cores and I wasn't able to find a source for just two bobbins.

The bondout wire would be a problem either way. These are 34AWG wires and I probably flexed it too much when I was testing it.

Lesson learned, attach lead out wires and finish taping before messing with measurements.
 
Two transformers are finished. There is a difference in that one has two 200 turn secondaries in parallel, and the other has two 100 turn secondaries in series.

It will be interesting to see what the difference is other than dampening factor (due to DC Resistance of the windings).

They measure within 0.3dB of each other.
 

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Still working on a headhpone amp, progress is slow.

Progress is very slow dut to life intervening on hobbies.

I finally have the terminal boards done for one channel to test the design. Trial layout on the chassis I was hoping to use looks really cramped.

I expect I'll have to go to a larger chassis, probably 12" X 12" and possibly sheet Al top with wood surround.

Mean time, I'm going to wire up one channel on the bench and see how it sounds. Possible tweaks will be evaluated.
 

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My interstage transformers . . .

Eventually I have go them done, but for a different project. This one is going to be used with an EL 84 triode connected driving a quad set of EL84's - single ended. It's a step down, 3:1.
 

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Progress is very slow dut to life intervening on hobbies.

I finally have the terminal boards done for one channel to test the design. Trial layout on the chassis I was hoping to use looks really cramped.

I expect I'll have to go to a larger chassis, probably 12" X 12" and possibly sheet Al top with wood surround.

Mean time, I'm going to wire up one channel on the bench and see how it sounds. Possible tweaks will be evaluated.

Well Monsieur Le G, How did your interstages turn out? Inquiring minds . . . .
 
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