[E55l2]

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[Unison845]

Tango X10S Inductance

[Unison845]

GM70 amp, Tango xformer in action X10S/NC20/845 in action, @ full power 30W freq response.

[Unison845]

Tango NC20 Inductance.

[E55l2]

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[Jon L]

Lundahl transformer upgrade for Eleket TU8600R 300B SET.

0609201205_HDR by drjlo2, on Flickr

[Tyson]

Lundahl transformer upgrade for Eleket TU8600R 300B SET.

0609201205_HDR by drjlo2, on Flickr

Oh man I am jealous!

[E55l2]

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[E55l2]

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[FullRangeMan]

Hi E55L2,
Just found this odd 300B SET which use PushPull OPTs and small vintage power transformer that use very thick EI lamination. What do you think?
http://www.glowinthedarkaudio.com/john-hogan-fiprimer-300b.html

[Docere]

https://www.lundahltransformers.com/wp-content/uploads/datasheets/2770B.PDF

This is the datasheet from Lundahl

From the datasheet i read the induction is 45H at 60mA with Ra=3200 Ohm (45H is way to much) Lundahl says B=0.9T at the static current of 60mA.
This means that they need a lot of windings to get the 45H on such a small core and the airgap is just 0,14mm
I doubt this works good* and if it works the saturation comes very soon. If you have a amplifier >50Hz this would probably be ok but i think lots of people like to have FULL range from 20Hz.

* i am pretty sure it sucks

Hi E55L2,

Thanks for the information you are providing here.

Interesting comments regarding the 2770B: 45H where Zp=3K2 Ohm does seem high, though probably not a challenging wind and high-frequency performance may not suffer much? I use a rule of thumb that inductance target >= Zp/100 (at operating current). Or put differently: 10Hy or slightly more per 1KOhm of Zp. In my designs, this generally means ~40Hy per 1KOhm rp. My experience is limited, but this has worked for me in the past: the 4K2 Nano-C cored output transformers in my current SET amplifier are 45Hy at the operating current; they seem to get the balance about right and bandwidth is good.

Edit: removed some content re my next transformer set.

[E55l2]

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[FullRangeMan]

If they use a constant current source to balance the transformer it could work but my god what a total disaster that amp must be. Just save the tubes and the rest is garbage.

I noted each channel have a hum pot to lower the circuit noises 
I would not be surprised if it was done with PCB due cheap parts everywhere.
This site always show interesting amps and FR drivers.

[E55l2]

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[FullRangeMan]

This small 2kilo EI Hashimoto inform Pri inductance 10H.
http://www.tube-amps.net/HP_HC203U.htm

[E55l2]

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[FullRangeMan]

E55L2,
This isolation paper is Tercott or what?

[E55l2]

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[FullRangeMan]

Thanks bro these links are useful
Tercott are some yellow/brown colour specified 130ºC and dielectric.

[E55l2]

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