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VeightTripleDivision 11th September 2021 11:46 PM

Yes, correct.

xrk971 12th September 2021 12:34 AM

1km roll!!! Thatís enough to make inductors for 10 lifetimes. :)

nautibuoy 20th October 2021 09:50 PM

Hi X I would like to try a LuFo Lite as an HPA for use with my 600ohm BeyerDynamics - can see any problems with that?

xrk971 21st October 2021 06:37 AM

No, unless you need really high SPL levels. As impedance goes up, the amp needs to provide more voltage swing. With a 15v supply, you should easily get up to 20vpp and that should be more than enough for 600ohm Beyers. Assuming we use the 16vpp simulation results, that is 5.6Vrms or 52mW into 600ohms.

Assuming the Beyer’s have 96dB sensitivity at 1mW, 52mW is about 5.5x3dB or 16.5dB. Or 112.5dB SPL - more than loud enough for most music.

I think it’s going to work fine. You need a good preamp capable of 16vpp though.

nautibuoy 21st October 2021 06:43 AM

Thanks X. High SPLs are not conducive to long term appreciation of high quality music so not a requirement. With a 600ohm load the output cap requirements move into plastic film territory too.

xrk971 22nd October 2021 12:34 AM

Yes, 100uF film cap will be flat down to 10Hz (2 octaves above 2.5Hz -3dB point). A couple of 50uF MKP caps can work here. Or two 50uF appliance motor run caps would work too.

xrk971 28th October 2021 12:48 AM

I replaced the power resistor R3 with a 12v 20w halogen light bulb. I increased the rail voltage to 20.0v (used 24v SMPS brick upstream of cap Mx). This ends up with 1.63A bias current and 12.9v at the LU1014D source and 12.0v at the light bulb. About perfect for an amp! Fortuitous situation.

No resistor heatsink needed! Lots more headroom on the amp now.

Doubles as a desk lamp! :)

xrk971 28th October 2021 02:11 AM

1 Attachment(s)
I am testing it out with 50ohm headphones now (OB-1) and it sounds great. Absolutely silent background with music off. Nice and clear, engaging and powerful.

xrk971 28th October 2021 12:41 PM

1 Attachment(s)
I think one can stick the halogen bulb right where X133 is and eliminate the off board resistors. Running with 24v SMPS (or linear supply) gives the correct bias current now. Place the lightbulb here:

xrk971 29th October 2021 07:02 AM

LuFo Lite Manufacturing Data
4 Attachment(s)
As I have determined that LuFo Lite works fine with a proper resistive load or a halogen light bulb (12v 20w), I think the current Gerbers will work as-is.

Here is the manufacturing data including Gerber files for anyone wishing to order their own PCB's. I might have some in my shop at some point in the future as well.

A big thank you to JPS64 for another superb layout.

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