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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 21st November 2020, 11:18 AM   #261
mokaonli is offline mokaonli  France
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Default My amp Noir

Hello,
I left aside my F6 while waiting for the arrival of the new JFETs, and started building the Black amp, and here it is.

Due to a problem with the blue Alps, which is totally asymmetrical, it will go to after-sales service, I replaced it temporarily with 2 10k.
the amp sounds beautifully on my Focal Elegia headphones, I rediscovered this headphones.

On the other hand, I did not use the SMPS power supply, but a more conventional power supply (toroidal 15v and 20,000uf Nichicon KG capacitor) to power it, I only have 22v in output, I don't think that the affected.

I am waiting for another power supply with 84 capacitors to finalize the assembly. and I reserve a subtle dressing for it, I will post the photos when it is finished.

Thank you so much Mark
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Old 21st November 2020, 12:19 PM   #262
avtech23 is offline avtech23  Australia
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Nice.

It's good practice to elevate the 68 ohm resistors a little from the board so they don't cook it too much.

Will be interested to hear your impressions with the final PSU installed.
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Old 21st November 2020, 08:38 PM   #263
mokaonli is offline mokaonli  France
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I reassure you, they are well raised from the circuit, 5mm to be precise, it is the photo taken from above which crushes the perspective.
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Old 21st November 2020, 10:07 PM   #264
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Wow you used the SMD version of the Current Regulator Diode! Congratulations.
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Old 3rd December 2020, 12:25 AM   #265
daveopen is offline daveopen
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Default Question about my build results

I'm new to electronics and high quality audio. The Noir was a lot of fun to build. The instructions were great and the layout of the board was very nice.
I learned a lot.

So, I'm not sure if I built the Noir correct or not. I was able to bias both channels and the power seems OK. I just received Beyerdynamic DT-990 250 ohm headphones (my first nice pair of headphones.) I'm using a Samsung Galaxy S10e direct input into the Noir, and plugging the phones into the 1/4" output jack.

The volume control works, but I have to turn the volume knob almost all the way up to get the same sound level that I get with just plugging the headphones directly into the Samsung. The Samsung is at about 3/4 volume.

The amp is very quiet, and the sound quality does seem to be enhanced. Don't take this the wrong way, but do you think that I have a problem? Or, is this to be expected, i.e. more about the audio quality than the volume?
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Old 3rd December 2020, 09:45 AM   #266
avitkauskas is offline avitkauskas  Lithuania
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Hi Dave.

Your Noir is just fine. The gain of Noir is just 6dB, that is 2 times in voltage, so don't expect too much of amplification or loundness. But let's see it the other way round: volume control is not about making the sound louder, it's vica versus - it's an attenuator, so actualy volume control is about making the sound level lower. Maximum volume could be regarded as a "normal" position of the volume control - no attenuation. You turn it to the left to make the sound level lower when it is too high for you Therefore, if your normal listening volume is close to the rightmost position of the volume control - it's marvelous, that means you are not "throwing away" much of a signal

One more thing. When sourcing the signal from the phone, put the volume on the phone to maximum. Digital music quality is the best when you do not digitaly attenuate the output level. Then you control the volume on Noir. That should give you max quality.

Concerning the sound quality of Noir, I would say that no amplification device can improve the signal quality - any amplification can only add some distostion, not to make less distortion that it was in the source. Therefore, Noir is not making you phone output signal better per se, but it does make it a bit different. And if you like this difference - that's fantastic! Enjoy it!
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Old 3rd December 2020, 11:15 AM   #267
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
In fact the max-possible-gain of Noir was designed to be low enough that, for most people and most headphones and most signal sources, the comfortable setting of the volume control would be between 50% and 100% of max-clockwise-rotation. That's where the two halves of the Alps Blue Velvet potentiometer exhibit the best tracking.
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Old 3rd December 2020, 12:50 PM   #268
daveopen is offline daveopen
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Great! Thanks Mark and Avit. The learning process continues. Mark, you've created a very nice product. If I can build it without botching anything, then anyone can build it.
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Old 3rd December 2020, 05:38 PM   #269
Mark Johnson is offline Mark Johnson  United States
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Noir, a two transistor headphone amp: class-A, single ended, 150mA bias
Thank you Dave! Noir is aimed at folks just like you, I'm thrilled your build was a success and you enjoy the music it makes. When you show your hand built Noir to friends, remember to say "there are only four transistors inside this box; two for the left channel and two for the right."
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Old 7th December 2020, 11:21 AM   #270
LotsOHiFiFun is offline LotsOHiFiFun
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Default Custom Case

Here is my final build of the Noir with a custom case.

Aluminium angle from the hardware store on front and back, brushed with the green side of sponge scouring pad and then coated with
clear gloss floor varnish. I put the Meanwell power supply inside the case, no reason, I just like it that way and
have experienced no noise. In fact I could detect no background noise in normal use at all. Only had one issue with parts ordering
see photo.
being that I was sent 20k trimmer resistors instead of 200k. I noticed the value on top after soldering and thought this doesn't look right and got out the multimeter.
Sure enough they were 20k. I checked the packet and it was clearly marked containing
200k. Luckily I hadn't powered things up at this stage. The local electronics store had just opened again
after the pandemic rules here were relaxed and they had the right part in stock and with the adjustment screw on the top... rather then
the side... Phew!

Anyway it's all now done and sounds smooth and sweet right through the whole frequency range. Music pace was a surprise, showing me why
some songs sound more atmospheric when played slow and I don't recall ever noticing that before. The amber led is a nice touch
giving a nice old fashioned incandencent glow. I like my Sundara's best with it, but it doesn't seem to be too fussy, Neo 99's and even Mr Speakers
sound good too. As a preamp it's fine, but not as good I feel as the B1 in that role.
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