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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 16th November 2019, 04:22 PM   #31
ernesternest is offline ernesternest  Europe
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Good afternoon,

After a few hours of work I could finish my Noir build today. As Mouser does not ship the recommended wallwart to Europe, I ordered a Meanwell with equivalent specs.

Bias es easy to set to 150 mA and so I went on listening after bias had stabilised.

First tunes over my AKG 712pro were not to talk about, yet it became more soud after a while. So I am curious about how it will sound after some forming hours.

I noticed that the psu cap in the amp is just 330 uF. Somehow I feel inner motivation to put a bigger one on its place. Would this benefit the sound in any way?

Cheers

Ernst
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Old 16th November 2019, 06:53 PM   #32
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Ernst, many SMPS wall warts contain short circuit protection circuitry, which falsely triggers if there is "too much" capacitance connected across the supply output pins. For example, the "ACP+" project from Burning Amp 2019, connects about 4000 uF from supply to ground, and this is enough to make the wall wart sputter and belch. They're using 24VDC @ 0.5A. If you experiment with larger and larger amounts of bypass capacitance, it would be wise to unplug the headphones before turning the unit on or off!

On the other hand, why not try it? The worst that can happen is: you'll find out how much capacitance is too much. You'll also find out whether you detect any improvement or degradation in the sound.

_
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Old 16th November 2019, 09:38 PM   #33
ernesternest is offline ernesternest  Europe
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Thanks Mark for your detailed answer! And thanks for this well documented, complete and easy to build project.

I will play a little bit with it. Maybe I will add some crc part.

Cheers

Ernst
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Old 17th November 2019, 02:34 PM   #34
PjVervoorn is offline PjVervoorn  Thailand
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Quote:
Originally Posted by Mark Johnson View Post
PjVervoorn, I haven't tried the modifications you propose, and I don't think anybody else has either.
...
Hi Mark,
Thanks for your response.
I will start with the specified values and see if I want to experiment.
The batteries are 7.9Ah (replacement UPS batteries), that would virtually double the playing time with the same drop.
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Old 18th November 2019, 07:13 PM   #35
ernesternest is offline ernesternest  Europe
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
A few pics of my amp. Even they might all look the same ;-)

Cheers, Ernst Attachment 795908IMG_20191116_195252.jpg
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Old 18th November 2019, 07:21 PM   #36
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Congratulations on a beautiful build, Ernst! I like your idea to rotate the 6.35mm headphone jack, it made your wiring extremely clean and tidy. It also looks like you are using a "DACT stepped attenuator" volume control. Kudos for personalizing your unit!

Mark
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Old 18th November 2019, 08:16 PM   #37
ernesternest is offline ernesternest  Europe
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Mark,

Your kind words make me happy! Yes, this is a DACT type attenuator. I like them as they are more matched channel wise, even I wish they were a bit more logarithmic...
And I use old MKC foils. ZM likes them, so I like them ;-)

Cheers, Ernst
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