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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
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Old 15th January 2021, 04:37 PM   #281
6L6 is offline 6L6  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Nior is positive ground.

EDIT: Also, Nior is going to ignore the PSU input reversal as the on-board PSU filtering ignores input polarity and makes it positive earth.

Last edited by 6L6; 15th January 2021 at 04:47 PM.
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Old 15th January 2021, 04:51 PM   #282
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
6L6 is correct, the design of Noir assumes (requires) its own dedicated SMPS. Some builders have put their Noir PCB into the same chassis as a brick-style SMPS, in which case the external source of power is an AC mains line cord.

The Mean Well EPS-25-24 (link) is one possibility; its size is 3 inches by 2 inches.

And there are lots more to choose from; a preliminary search on DigiKey found 131 candidates to study further: link 2



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Old 15th January 2021, 04:57 PM   #283
muskyhuntr is offline muskyhuntr  United States
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Back to the drawing board!
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Old 25th January 2021, 07:23 PM   #284
avitkauskas is offline avitkauskas  Lithuania
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Hi Mark and others.

I had time to come back to the "problem" of the glowing LED described in the post #275

I measured some voltages and found out that when the power supply is connected, Noir is switched off, and other-audio-gear with the grounded output is connected to the Noir input, I have 2.35 VDC accross the LED, and that makes it glow faintly. The glow does not start immediatelly - it takes some 8-10 sec to start glowing, as some capacitor charges up and then gives the voltage accoss the LED.

I also measured the AC from the negative rail of the power supply and the ground and got ~1.5V.

Yes, this can be solved (or rather hidden) by putting 200R resistor in paralled with the LED - with the resistor in place the LED does not glow. I tried this.

But the most worrying thing is that Noir does not work at all with the other SMPS (Mean Well 24V, 5A - the one that was supplied by the diyAudio store with the ACA) when connected to the other equipment that is grounded. This SMPS starts blinking as if some protection kicks in and pulsates in 2 sec cycles. Therefore I find it not being ok to just stick the resistor and forget it, as it shows that (at least mine) Noir is not usable in some conditions.

I like the sound of Noir very much, so I would like it to be "foolproof". My knowledge is not good enough to understand what is causing the problem and how it could be eliminated for sure rather than just hidden.

Would be glad to try something else if somebody gives some ideas to try.

-Alvydas
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Old 25th January 2021, 09:05 PM   #285
avtech23 is offline avtech23  Australia
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Hi Alvydas, do you have photos of the top and bottom of your assembled PCB you can upload here to make sure nothing is amiss?
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Old 25th January 2021, 10:19 PM   #286
avitkauskas is offline avitkauskas  Lithuania
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Here it is...
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File Type: jpg IMG_2411.jpg (965.7 KB, 46 views)
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Builds: ACA, M2X, F5 by Nelson Pass, Noir by Mark Johnson, Akitika PR-102, GT-102 by Dan Joffe, Overnight Sensations by Paul Carmody
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Old Yesterday, 01:06 PM   #287
mokaonli is offline mokaonli  France
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As promised, I come back with some photos of the project, it was long, and complicated and it's not over.

The general design is not mine, you can find it at "LIEDSON", I still modified the curves, the angles and the size, added aluminum between the sections.
It is controlled by an ARDUINO, which allows me to manage the inputs / outputs with an impulse on the volume button, as well as the management of ON / OFF with the push button at the bottom.
I use a 64-step "KHOZMO" relay attenuator, the supplied remote control has a 5th ON / OFF button, I got its code to control the ON / OFF from the arduino using an IR LED .
I inserted a passive Pre-amp output for my F6, the power supply is composed of an R-CORE transformer and 64 capacitors for a total of 10 000uf.

When I said that it was not finished, it is because I faced difficulties with the wood (fir) which is too fragile, and difficult to machine.
I started on this wood because I wanted to keep the grain along the entire length of the block.
So I am going to redo another block this time in American Walnut, a noble wood, easy to work, I will work it this time on glued edges of 40 to 50mm and the result will be even more beautiful.


Regarding listening, I was able to test it with 3 different power supplies, SMPS and classic with 20,000 and 10,000uf, the classic is beautiful, soft and pleasant.
The 10,000uf version is the one I prefer, it adds a hint of bass, while the 20 000uf version becomes fatigaunte on long listening, more the multiplication of the capacitors, allows to obtain more precise bass, very pleasant.

The negative point, I still have a buzz of present, very light, I only hear it on the ELEGIA, on the ELEAR it disappears, probably due to its low impedance (more sensitive).
In addition I pick up a series of frequencies spaced 40 sec apart, so I am considering a faraday cage, what do you think?
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Old Yesterday, 01:18 PM   #288
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Gorgeous build, mokaloni! You have carved a work of art.
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