xrk971 Pocket Class A Headamp GB

[xrk971]

You mean matched IRF610’s? I did not have them matched at present but suppose I could.

 

[stellarelephant]

Yes. If possible, matched pairs of both BF862 and IRF610 would be a big help.

 

[MadHatterRyu]

Hey there
Just confirming but the desktop variant will be a 12V DC in and not a transformer + rectifier right? Because I'm thinking of building one and feeding it with an ifi ipower.

 

[xrk971]

Get one of these units and place inside the amp case between the DC input jack and the amp and you can feed it with anything from 9v to 19v. Adjust for 22v output such that the output from the cap multiplier and after the CRCRC is about 18v into the amp. I have found that a Class 2 rectified 12v 800mA transformer with a 5.5mm barrel jack from GCI is one of the quietest sources to power this with. The 1000mA version works well too.

GCI TechnoLogies 12V 800mA AC to DC Power Supply Adapter Transformer AM-12800 | eBay

DC to DC converter:
250W DC DC Boost Converter Adjustable 10A Step Up Constant Current Power Supply Module Led Driver For Arduino-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

or similar...

These work well too:
400W DC DC Step up Boost Converter Constant Current Power Supply Module LED Driver Step Up Voltage Module-in Inverters & Converters from Home Improvement on Aliexpress.com | Alibaba Group

 

[xrk971]

For those of you waiting for the Pocket Head Amp PCB, my supplies just got restocked and you can place orders on my shop.

 

[pcgab]

X,
are you doing a gb for the new desktop boards? If so, I would definitely like one.

Cheers,
Gable

 

[xrk971]

Hi Pcgab,
Great - I think I will just sell them from my shop - it makes tracking the order and logistics a bit easier. I will put up listing soon.
Thanks,
X

 

[xrk971]

Desktop Amp PCBs are Here

I just got the nice 2mm thick, 2oz copper, gold ENIG finish with blue solder mask today. Very thick boards perforated with JPS64's signature vias for extra low impedance on high current paths and ground planes. Only one issue: the boards are lacking silk screen. We will provide a separate stuffing guide image - it should not be too hard to stuff. My mistake for not catching that the Gerber fileset was missing the silk layer before placing the order.

I will be offering these amp boards for $23 ea on my Etsy shop. Shipping will be by weight and locations as determined on Etsy.

SE Class A Desktop Amp PCB

 

[MadHatterRyu]

If you're selling the desktop kit too, I'm in
Can wait but some of us are looking for matched FETS for the portable version. (we're patient no problem)

 

[yourownbuzz]

Hi X,
Are you still posting them in an envelop? The postage to Aus is fairly steep - I added 2 boards to cart and postage is $27! From memory when you sent the PCA boards postage was a lot less?

 

[xrk971]

Let me check out how they are doing the postage - should be less I agree.

 

[xrk971]

YOB,
Please check shipping now to OZ, should be more reasonable.

 

[xrk971]

I just got the nice 2mm thick, 2oz copper, gold ENIG finish with blue solder mask today. Very thick boards perforated with JPS64's signature vias for extra low impedance on high current paths and ground planes. Only one issue: the boards are lacking silk screen. We will provide a separate stuffing guide image - it should not be too hard to stuff. My mistake for not catching that the Gerber fileset was missing the silk layer before placing the order.

I will be offering these amp boards for $23 ea on my Etsy shop. Shipping will be by weight and locations as determined on Etsy.

SE Class A Desktop Amp PCB

Here are the visual stuffing guides:

3D rendered version of what board should have looked like with silkscreen:

Schematic:
Click on thumbnail below.


I’m still working on the BOM. Will post it shortly, but if you look at the schematic you can get most stuff there. All resistors are 1/4w 1% metal thin film except for power resistors which should be at least 1w. All electrolytic should be minimum 25v but preferably 35v. For best sound quality the output elcos should be 35v to 50v rated. Elna Silmic II or Panasonic FR or Nichicon KA are all good.

 

[yourownbuzz]

the shipping costs still look the same - heres a pic of what im seeing

 

[xrk971]

Sorry about that - I must have not saved the new shipping profile. Please try one more time.

 

[pcgab]

I just got the nice 2mm thick, 2oz copper, gold ENIG finish with blue solder mask today. Very thick boards perforated with JPS64's signature vias for extra low impedance on high current paths and ground planes. Only one issue: the boards are lacking silk screen. We will provide a separate stuffing guide image - it should not be too hard to stuff. My mistake for not catching that the Gerber fileset was missing the silk layer before placing the order.

I will be offering these amp boards for $23 ea on my Etsy shop. Shipping will be by weight and locations as determined on Etsy.

SE Class A Desktop Amp PCB

Awesome! I just ordered a few, looks like a fairly simple build.

Cheers,
Gable

 

[xrk971]

Thanks, Pcgab! It really is a simple amp - with only two transistors per channel you really can’t make it hard. Well there is the extra 5th one for the cap multiplier.

 

[pcgab]

Thanks, Pcgab! It really is a simple amp - with only two transistors per channel you really can’t make it hard. Well there is the extra 5th one for the cap multiplier.

Ha, I think I can handle that. I think I probably have a good bit of the parts on hand, will confirm once you post the bom.

 

[pvs]

I just ordered one of these PCBs for what will be my first DIY audio project, one of my first electronics projects altogether actually.

I began ordering some parts in advance a little bit ago.

It took a surprising amount of digging, but I did manage to find what seem to be good Chinese equivalents of the mechanical components, at a big discount.

10pcs B10K RV097GS Audio Amplifier Sealed Dual Potentiometer 15mm Shaft 8PINS | eBay

20PC 5pin 3.5mm Jack Stereo Headphones Socket nut Panel Mount Chassis PJ325M | eBay

The jacks haven't arrived yet, but the pots have. Make sure you tell the guy to use a little bit of foam else they'll come with bent pins like mine.

I was also able to find the SMD resistors and caps and the JFETs from lcsc.com, also at a steep discount. They haven't arrived yet but I've ordered from them before and they're solid.

For the rest of my BOM, sans the 1uF caps which I also got from eBay, I got gouged by Digikey.

Get one of these units and place inside the amp case between the DC input jack and the amp and you can feed it with anything from 9v to 19v.
DC to DC converter:
250W DC DC Boost Converter Adjustable 10A Step Up Constant Current Power Supply Module Led Driver For Arduino-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

What's the current draw on the PCA? Because I have a bunch of these boost modules already, and they emit audible whining boosting 5V to 12V starting at .2A, and it becomes deafening at .75A. It comes from the coil best as I can tell.

 

[xrk971]

Those Chinese parts can work but the pot and headphone connector are critical to sound quality as bad pots are not linear and can actually add noise and distortion. The genuine ALPs was $3 I think so you are saving if you make more than two. The 3.5mm jacks by Switchcraft are actually machined brass that is nickel plated. They engage well and don’t have scratchy noise. They are $5/pair. Pricey but not in the scheme of things.

I also buy and use inexpensive Chinese parts - mostly on prototype P2P serial number 0 jobs. Then I use higher quality stuff for next builds to get best performance.

Just don’t let the poor mechanical contact ruin your low noise SE Class A sound.

You need about 200mA to work with DC step up. Get ones that don’t whine. That’s not acceptable.