Noir, a two transistor headphone amp: class-A, single ended, 150mA bias

[PjVervoorn]

Ordering a Noir on Black Friday is the right thing to do...
One set with chassis will soon be on its way to Thailand.

 

[batty]

Mine.

Set the bias to 5.1 volts and left it overnight, this morning it reads 5.106 and 5.107.
Gotta be happy with that.

 

[adydula]

Well congrats on your build!!

How does it work "sound" etc....

Alex

 

[Mark Johnson]

Good on ya, batty!

 

[fmmech_24]

mark johnson,..thank you for your work!

This is my Prototype, based on your T2/Noir..

 

[Mark Johnson]

Great job, fmmech_24! You're going to have a lot of fun with your HPA design!

You might want to experiment with different bias voltages and currents than the standard Noir, since your HPA will operate on a lower supply voltage than Noir. Different supply, different optimum bias point.

The IRF510 in your supply smoother, has a fairly large gate-to-source voltage drop. Thus the supply smoother has a fairly large input-to-output voltage drop, perhaps on the order of 4.0 or 4.5 volts.

_

 

[PjVervoorn]

I have ordered the items in the Mouser basket, save 2 items as these weren't in stock.

For the Alps (delivery expected Februari 2020) I chose as temporary replacement:
1688-RK16312A0B85
RK16312A0B85
ALPS Potentiometers
And for the Littelfuse I chose:
650-RXEF050-2
RXEF050-2
Littelfuse Resettable Fuses - PPTC

If there are better alternatives at Mouser, please advise, for other builders.

 

[miep]

Hey fmm. There is a problem in your circuit. You are about to put the 24v to the Output. Also the bleederresistor is in the powersupplyline. Not on ground as it have to be. Dont know if it is a drawing problem or a "real" problem

 

[Mark Johnson]

PjVervoorn: those look like good choices. US and Canada buyers can also buy the ALPS Blue Velvet potentiometers from Parts Express (here is a LINK), maybe they will also sell to customers in Thailand (?). And of course eBay sells lots and lots of Blue Velvet pots, we just don't know whether they are counterfeit or genuine.

 

[PjVervoorn]

Hi Mark,


Thanks. Yes, Thailand it is. I plan to replace the Alps when the Noir is a keeper (comparing to the O2.)
Then I can just add it to another Mouser order and avoid both fakes and shipping costs.

 

[nenad88]

mark johnson,..thank you for your work!

This is my Prototype, based on your T2/Noir..

My MAN I love when gerbers are below 10cm x 10cm

 

[Ben Mah]

Looking at the power supply schematic shown in Post #1, it looks like the polarity of DC output of D2 is reversed. No doubt the pcb is correct as many amps have been successfully built.

 

[Mark Johnson]

Yes you're right, thanks for the catch! The PCB is correct, and so is the schematic in the PCB CAD system, but the "make it pretty for human readers" version of the schematic for documentation, is upside-down. I'll fix it.

 

[batty]

I have just tried out my Noir for the first time, source was a squeezebox touch and phones are AKG Q701, Totally amazed at the SQ of this amp. well done guys.
THANK YOU.

 

[Mark Johnson]

Congratulations, batty! Hope it was a quick fun job to put Noir together, and I'm thrilled you are pleased with the results.

 

[halusha]

The ferrite core is out of stock at Mouser. Any easy replacement?

 

[Mark Johnson]

The ferrite core is out of stock at Mouser. Any easy replacement?

Since you're in the US, the best idea is probably to just buy it from DigiKey (LINK).

Maybe the second best idea is to buy Mouser part number 710-74270035 , keeping in mind that its diameter is much larger than the Laird bead which the Noir PCB is designed to fit. I expect it might be a little tricky to thread a plastic cable tie through the mounting holes on the PCB, encircling and securing such a wide core. But you may prefer this kind of challenge, rather than placing a DigiKey order. Extra long (8" , 200mm) zip ties might be useful here since they allow you to have plenty of "slack" above and below the board, and yet be able to mate the two ends, as you're positioning the coil and gradually tightening the zip tie. Amazon Link

 

[avtech]

I used this one from fair-rite, which had very similar specs to the original (both physically and electrically) and did the job just fine for me:

https://www.newark.com/fair-rite/26...5023002&ddkey=https:en-US/Element14_US/search

They have stock for about 50c US.

 

[Mark Johnson]

In case that link doesn't work, go to the website of Newark / Element14 and search for

2675023002

which is the manufacturer's part number, or

70W1676

which is the Newark part number

That's the replacement which member avtech23 is suggesting.

 

[halusha]

Ordered from DigiKey, thanks!