"Millett Hybrid" redux: NuHybrid headphone amp, using the Korg Nutube
Jul 15, 2017 at 1:28 AM Post #122 of 492

trevmex

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Got the upgraded pot and the EARs. Now I'm ready to go!
 
Jul 21, 2017 at 6:01 AM Post #130 of 492

trevmex

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As promised, here are the progress pics!
Photo Jul 20, 11 54 55 PM.jpg Photo Jul 21, 12 20 36 AM.jpg Photo Jul 21, 12 41 19 AM.jpg Photo Jul 21, 1 13 34 AM.jpg Photo Jul 21, 1 42 13 AM.jpg Photo Jul 21, 1 42 28 AM.jpg Photo Jul 21, 1 55 22 AM.jpg Photo Jul 21, 2 43 44 AM.jpg Photo Jul 21, 2 43 34 AM.jpg
And there you go. I don't have the right headphone connector to test it at home, so I'll let everyone know how it sounds tomorrow.

I highlighted hav2uo4's pot ground wire and the EARs. Hope they make it sing!
 

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Jul 26, 2017 at 11:59 AM Post #133 of 492

Evgeni

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Guys, you were right about solving noise issues by grounding the pot: that solved my problem. However I haven't applied this fix permanently (like on the hav2uo4's picture above) yet, I just tested it with a wire. But in the meanwhile I replaced the switching supply with a linear supply I ordered from eBay and that kind of halved the noise.

However I am currently totally noise-free. Here's the "fix". I was mainly using my NuHybrid with my HD-650. However I recently bought Beyerdynamic DT-880 600-ohm and man, that's a combination made in heaven! The Beyers just sound incredible, it's a butter creamy sound. I can't hear them sound this way with any of my other amps. This amp really shines with these headphones. Really, guys, you MUST try this combination, it's probably my best setup ever! And they are absolutely noise free this way which I contribute to high-impedance (and low-sensitivity).

BTW, I tried to change the bias through the trims while listening to music and I can't hear any change whatsoever. It's either the harmonic content change can be noticed only with an oscilloscope and not audible or it's my ears (or I don't know what to listen for). But right now I just followed Pete's advice to set them at 11V.
 
Jul 26, 2017 at 12:16 PM Post #134 of 492

hav2uo4

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I just tried the NuHybrid out with my Grado SR60i phones. Sounds great!!!

Now, I want to put a clear plastic lid on the setup with some slits for air to get in. Can anyone recommend a place to get a plastic lid for the box Pete suggested?
Build looks awesome, nice job. Glad it's working out for you. Not sure about a plastic lid. Data sheet seems to suggest that isolation from the air (no slits) can be better for microphonics (I smacked a fruit fly ~10ft away and it started ringing...haha). But the regulator does get toasty, it probably needs some airflow (I squeezed a heatsink on mine which is somewhat visible on the previous picture I posted).
 
Jul 26, 2017 at 12:24 PM Post #135 of 492

hav2uo4

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Guys, you were right about solving noise issues by grounding the pot: that solved my problem. However I haven't applied this fix permanently (like on the hav2uo4's picture above) yet, I just tested it with a wire. But in the meanwhile I replaced the switching supply with a linear supply I ordered from eBay and that kind of halved the noise.

However I am currently totally noise-free. Here's the "fix". I was mainly using my NuHybrid with my HD-650. However I recently bought Beyerdynamic DT-880 600-ohm and man, that's a combination made in heaven! The Beyers just sound incredible, it's a butter creamy sound. I can't hear them sound this way with any of my other amps. This amp really shines with these headphones. Really, guys, you MUST try this combination, it's probably my best setup ever! And they are absolutely noise free this way which I contribute to high-impedance (and low-sensitivity).

BTW, I tried to change the bias through the trims while listening to music and I can't hear any change whatsoever. It's either the harmonic content change can be noticed only with an oscilloscope and not audible or it's my ears (or I don't know what to listen for). But right now I just followed Pete's advice to set them at 11V.
Interesting PS observations, Evgeni. I got some promising results with another method. I was trouble-shooting some noisy Russian tubes on my project amber amp and found that my noise problems went away when I ran a ground wire from my mains line to the negative out from the switching regulator (be super careful if trying this). Dead silent. Tried it on my nuhybrid with the same results. Crazy quiet! Now my work computer sound card seems to have an unreasonable noise floor! YMMV, but I seem to have some really dirty AC.
 

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