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-   -   LuFo Lite - a 1 Transistor SE Class A Headphone Amp (https://www.diyaudio.com/forums/headphone-systems/374760-lufo-lite-1-transistor-se-class-headphone-amp.html)

marconi118 19th July 2021 01:08 PM

Would be interesting to find a commercial choke with 3ohm dcr so to avoid the resistor in series of the MOT...

xrk971 19th July 2021 04:21 PM

Actually you want 2ohms. 1.5ohm resistor plus 0.5ohm MOT. I think 220VAC MOTs are close maybe 2.5ohms? Also, Lundhal chokes made for tube filament heaters might be close to 2ohms also. Adding a resistor is not a bad thing. It’s better to drop that heat outside of the coil.

marconi118 19th July 2021 04:53 PM

Indeed 220v MOT would be nice: 2.5dcr and double inductance. Ideal for 16ohm speaker...
I have one lying around. Wil measure the dcr and report here

lineup 19th July 2021 05:50 PM

2 Attachment(s)
I have set up this amplifier in my Multisim Spice.
I get the same result. THD 0.008 %

The Fourier shows a nice 2nd harmonics.

nautibuoy 19th July 2021 07:19 PM

Quote:

Originally Posted by marconi118 (https://www.diyaudio.com/forums/headphone-systems/374760-lufo-lite-1-transistor-se-class-headphone-amp-post6725949.html#post6725949)
Indeed 220v MOT would be nice: 2.5dcr and double inductance. Ideal for 16ohm speaker...
I have one lying around. Wil measure the dcr and report here

I was also wondering about 240V MOTs - was about to post about it only to find these comments. I await your findings :up:

xrk971 19th July 2021 10:28 PM

At 2.35ohm I was getting only 900mA bias current through the LU1014D. But that would still be plenty for a headphone amp. A 220v MOT is a great candidate for a headphone LuFo Lite.

xrk971 19th July 2021 10:48 PM

Thanks for running that Lineup. Strange when I put your model in my simulation - I think it was the 8ohm case, I got 0.02% vs 0.04% THD. Still nice harmonic profile though.

lineup 20th July 2021 07:37 AM

1 Attachment(s)
I run your model now.
Possibly it gives closer to reality values.

May I ask why you run so much current, 1.72A ?
It is possible to increase the resistor values and get lower current and lower THD.
See image.

xrk971 20th July 2021 11:23 AM

Hi Lineup,
I am running 1.3A in reality and it’s high in order to be able to use as a fleawatt amp for 8ohm speakers. Several people expressed interest in an application as such. For headphone applications there is a lot less power required unless we are talking about the handful of cases such as the HE6 which requires up to 3w at 32ohms. But that will be voltage limited and not current limited.

Thanks for running the sim at lower bias current.

xrk971 20th July 2021 01:10 PM

Superb PCB layout that JPS64 is making for the LuFo Lite.
https://www.diyaudio.com/forums/atta...1&d=1626782758

Schematic here:
https://www.diyaudio.com/forums/atta...9&d=1626782840

Again, it’s more than a headphone amp but also a circa 5w speaker amp.


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