As JLC are almost giving away aluminium PCBs I think I'll adapt the TO247 adaptor board (that X and JPS devised) and do a version with the other LoFo-Lite components on it (that's the components around the LU1014D device, I'll leave the input cap off and obviously the choke and its associated resistor). The PCB will be larger but that may not be a bad thing as it will increase the area of interface with the heatsink. Obviously all the parts will need to be smd types.
Awesome news Jwjarch! It’s a simple circuit and not much to go wrong but things do go wrong. I had the same issue with a bad connection. Once that was fixed, music came out. Maybe what we need is one of those aluminum heatsinked resistors? Or maybe two 4.7ohms 10w in parallel and that should take the temps down. Those cement filled resistors can run hot but are a hand burn danger. As long as they don’t run above their 10w spec you are ok. They turn brown and smell funny when they run above their spec.
The sound is about as organic and natural as one would expect from a 1 transistor amp. At reasonable headphone power levels, the simulations predict quite low distortion circa 0.008% for 15mW into 32ohms.
My headphones are 96dB/mW so that’s plenty loud (108dB).
The sound is about as organic and natural as one would expect from a 1 transistor amp. At reasonable headphone power levels, the simulations predict quite low distortion circa 0.008% for 15mW into 32ohms.
My headphones are 96dB/mW so that’s plenty loud (108dB).
The sound was very clean and detailed as far as I could tell. In true XRK style I played some Metallica over a dual 3fe25-16 Mini-K. Worth building another channel for stereo I would say. I have some beefier resistors that I’ll try out, X. Here’s a photo of my current dead buggery.
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Way to go with playing Metallica on Karlsonators! Btw, try the 0.68mH and 4.7ohm BSC mod on the dual 3FE25-16’s. They round out the sound and give it some true bass.
I am going to wire up my second channel now. I have a lot 12v toroidal trafos and wondering if it’s worth trying that out instead of a SMPS.
I love simple amps. I think 3 of the gold anodized aluminum 8ohm 25w resistors in parallel would be 2.7 ohm load and would be perfect for spreading the heat out.
I am going to wire up my second channel now. I have a lot 12v toroidal trafos and wondering if it’s worth trying that out instead of a SMPS.
I love simple amps. I think 3 of the gold anodized aluminum 8ohm 25w resistors in parallel would be 2.7 ohm load and would be perfect for spreading the heat out.
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Agree on the BSC for the dual 3fe’s. The only problem for me is the extra bass starts to excite some resonance in the foam core cabinets. I probably didn’t use enough glue and or stuffing in some spots. I have also paired them up with a simple crossover and 15” open baffle woofers for the bottom end. Now that’s a great combo that really lets the 3fe’s sing.
I think the toroidal supply would work well. I might still use the CapMx with it. I’ve become a big fan of those on Class A amps. So quiet.
Off to experiment some more with the Lufo Lite. This is fun!
I think the toroidal supply would work well. I might still use the CapMx with it. I’ve become a big fan of those on Class A amps. So quiet.
Off to experiment some more with the Lufo Lite. This is fun!
Thanks Vunce! I finally built an XRK before you! Lol! Just kidding. This is so simple everyone should try it. Thanks for the great design X! Looking forward to getting the second channel done and hooking up to a real preamp.
The gold resistors are doing their job well. Overkill? Maybe... But it sounds fantastic! Running nice and cool. Each resistor is at 23.5C. Heat sink is about 30C.
The gold resistors are doing their job well. Overkill? Maybe... But it sounds fantastic! Running nice and cool. Each resistor is at 23.5C. Heat sink is about 30C.
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I built it in stereo and settled on 1.5ohm 2% 10W resistors for 1.3A bias current. I am only running 8v so the heat is not bad at 75C on the resistors.
Check out how close the bias currents are matched. The voltages on the two DMM’s show 1.948v and 1.945v across 1.5ohm 2% resistors. These are matched JFETs from the GB. The amp has no adjustments so it worked out well.
I connected it to my Khadas Tone Board 1 with ESS Sabre DAC and playing Ultra HD tracks from Amazon Prime. How does it sound? On my Status OB-1’s - totally blown away by how good it is!!! No noise silent background. Deep powerful bass, unending dynamics, clear mids and highs. Super imaging. Zero feedback amps are like that with imaging.
In short, this may be one of the best headphone amps I have ever heard. It is so simple you have to try it!
More details in its own thread in the Headphones Forum here:
https://www.diyaudio.com/forums/hea...istor-se-class-headphone-amp.html#post6725430
Check out how close the bias currents are matched. The voltages on the two DMM’s show 1.948v and 1.945v across 1.5ohm 2% resistors. These are matched JFETs from the GB. The amp has no adjustments so it worked out well.
I connected it to my Khadas Tone Board 1 with ESS Sabre DAC and playing Ultra HD tracks from Amazon Prime. How does it sound? On my Status OB-1’s - totally blown away by how good it is!!! No noise silent background. Deep powerful bass, unending dynamics, clear mids and highs. Super imaging. Zero feedback amps are like that with imaging.
In short, this may be one of the best headphone amps I have ever heard. It is so simple you have to try it!
More details in its own thread in the Headphones Forum here:
https://www.diyaudio.com/forums/hea...istor-se-class-headphone-amp.html#post6725430
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Update on sound of the Lufo Lite. Was just listening, in mono still, with my favorite preamp, The WHAMMY. I also put a BSC on the Mini-K just for kicks. 
This amp is really sounding good. So smooth and detailed. Listened to HD stream from Amazon through a Bluetooth receiver, so not the ultimate in signal to be sure. But I was able to pick out nuance in the music and beautiful tone in instruments. Max volume is limited in this current setup. I’m hoping in stereo in my main system with fairly sensitive speakers I’ll be able to get to satisfying volume. So amazing to be able to get this kind of power from a little power jfet.
This amp is really sounding good. So smooth and detailed. Listened to HD stream from Amazon through a Bluetooth receiver, so not the ultimate in signal to be sure. But I was able to pick out nuance in the music and beautiful tone in instruments. Max volume is limited in this current setup. I’m hoping in stereo in my main system with fairly sensitive speakers I’ll be able to get to satisfying volume. So amazing to be able to get this kind of power from a little power jfet.
Hi Jwjarch,
Wait till you hear it in stereo - the zero feedback amp has amazing imaging. For speaker driving duties remember that 2
19Vpp output is the max a plain LU1014D can do. If you need more swing, it’s easy to add a TO247 N channel MOSFET as a cascode. Then it becomes a regular LuFo (but for lower bias current it is ok to use a single MOSFET).
Also, be sure to try it as a headphone amp. Amazing sound.
I think JPS64 is already working on a PCB for LuFo Lite with built in Cap Mx.
Wait till you hear it in stereo - the zero feedback amp has amazing imaging. For speaker driving duties remember that 2
19Vpp output is the max a plain LU1014D can do. If you need more swing, it’s easy to add a TO247 N channel MOSFET as a cascode. Then it becomes a regular LuFo (but for lower bias current it is ok to use a single MOSFET).
Also, be sure to try it as a headphone amp. Amazing sound.
I think JPS64 is already working on a PCB for LuFo Lite with built in Cap Mx.
Hi Jwjarch,
I think JPS64 is already working on a PCB for LuFo Lite with built in Cap Mx.
I wonder if the option of the simple gain option as per this post
https://www.diyaudio.com/forums/pass-labs/372679-lufo-amp-39w-se-class-28v-rail-58.html#post6721750
might be something to include as an option - keeping to the spirit of LuFo-Lite?
As suspected, JPS64 was already on the prowl making a new LuFo Lite board
It looks wonderful, thank you, JPS64. There are a lot of options on this board such as Fastons, flying leads, or Molex MiniFit connectors for power, speakers, and MOT. There is an option for external heatsink mounted resistor or use the on board “fence post” style triple elevated resistor mount. Having a built in cap multiplier and CRC will give this amp excellent low noise performance and built in slow ramp up to prevent startup speaker pop.
It looks wonderful, thank you, JPS64. There are a lot of options on this board such as Fastons, flying leads, or Molex MiniFit connectors for power, speakers, and MOT. There is an option for external heatsink mounted resistor or use the on board “fence post” style triple elevated resistor mount. Having a built in cap multiplier and CRC will give this amp excellent low noise performance and built in slow ramp up to prevent startup speaker pop.
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Fairly similar amplifier to one I made some 19 years ago.
Choke loaded source follower works great!
--> My first ever Class A amp.
Choke loaded source follower works great!
--> My first ever Class A amp.