Call for small core permalloy parafeed preamp/headphone OPT

Design and use of the various types.
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regal
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Call for small core permalloy parafeed preamp/headphone OPT

Post by regal »

There is a hole in the commercial market with regards to low level (<2V rms out) high ratio small core output transformers.

For a lot of headphones a 0.5Vrms signal will put a whole in your eardrum. Yet we build our tube headphone amps with giant M6 cores that take no advantage of the low level signal w.r.t. the transformer design.

What we need is a parafeed permalloy on a small core so the details are not lost as when using a transformer designed for a 2W 45SET speaker amp.

A good permalloy parafeed 7k:32 on a core half the size we are used to seeing I think would be mindblowing. I mean you could offer an option for a 300 secondary for preamps builders, I bet they would be surprised at the detail they have been missing.

I could be wrong but I think a lot of preamp builders these days don't go above a 2V output, yet what we see on the market are 1W output transformers for preamps when we are dealling with milliwatts.

For headphones, preamps, and DAC's, tubes are linear enough without global NFB to compete with SS, yet the OPT's available are holding back the tube DIYers.
dave slagle
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Post by dave slagle »

people have been using the autoformer volume controls as headphone outs with good results.

dave
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bleeding.gums
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Post by bleeding.gums »

hi dave

i'm also looking for a small transformer for headphones.

you mentioned using the autoformers for headphone duties.

parafeed i assume? how do you work out the impedance?

thx!

bg
broken580
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Post by broken580 »

m way back) Does it need current cancellation or can it be gapped sufficiently to avoid saturation? I have a 12dB HP cross over at 500Hz but I still need 10 - 20H of inductance for a 10K load - going by Table 2 in RDHB4 - ie for min phase shift. I guess thats not possible from previous winds I have done, unless I get a lot more turns on. What
dave slagle
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Post by dave slagle »

It depends on how you want to use it.

Parafeed to an autoformer or series feed to a transformer.

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