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regal 18th February 2012 12:24 PM

Tubes: parafeed vs singlefeed
I had a transformer winder tell me something that made me think.

He prefers singlefeed opt's for headphones.

He said with single feed you only have 2 reactive devices - the OPT and the voice-coil. While with parafeed you are adding 2 (the choke load and the big parafeed cap) for a total of 4, which in his opinion is bad.

I guess I used to think way this as well, its a good point he reminded me of.

But with depletion mode n-channel mosfets for a CCS load and the relatively nice low cost various large size russian caps available today, the potential to run a transformer with higher inductance for a smaller core size.

I mean the CCS is good for linearity but the load is in parallel with the OPT, so if you start with a high quality shunt B+ are we really gaining anything with the CCS? PSRR that we don't need, and the load is dominated by the cap and transformer.

On the other hand I believe that the high secondary DCR that single feed headphone OPT's bring to the table is a negative. I think more than just damping but also detail loss.

I am really on the fence with this one, do I convert my existing amp to parafeed or just build a seprate parafeed version. (the prefiltered B+ is in a separate enlosure.)

Any opinions on this, or interested in the topic ?

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