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dsavitsk 19th April 2006 11:08 PM

Quick Output Transformer Question
I am going to use a pair of the Edcor transformers for a headphone amp. My headphones are 32 ohm, and I'll probably put a 32 ohm resistor in parallel. Do I need to do anything different to use the amp as a preamp? That is, will seeing a 10K, or a 50K input impedence cause reflection problems? Will I need to use a different resistor on the secondaries, or would transformers with a 600 ohm tap be a better idea? Thoughts?

leadbelly 19th April 2006 11:21 PM

These would work with a tube that could handle a 2K load:

I'm no guru, but the fact that they are interleaved whereas the $17 ones are not would work to your benefit.

dsavitsk 20th April 2006 01:05 AM

They are certainly cheap enough to try them both, so I may do that. If the tube wants a higher impedence, could I simply add a resistor in series with the headphones?

And, to the original question ... is the 16 ohm output okay as a line stage or will there be frequency problems?

Geek 20th April 2006 02:31 AM

You want the tubes to see a constant load for best fidelity.

Using an Edcor with an 8 ohm secondary, then paralleling a pair of 18 ohm resistors (9 ohms) will provide an excellent load match with 32 ohm phones.

I did some experiments with this on my 6FD7 amp, which has a switched headphone output and XSE15-8-5K's and it seems optimum.

ttan98 20th April 2006 04:36 AM

Hello fellows,

Do you know which company(ies) makes VERY high QUALITY transformers, single ended and Push pull, in the states and international?

Edcor?, Hammond? Sowter? etc

Geek 20th April 2006 07:08 AM

If you mean DC to daylight with zero phase shift ( :D ), I hear Lundahl is a good place to start :)

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