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Old 11-03-10, 08:38 PM
hacker hacker is offline
Delicious and nutritious
Join Date: Jul 2005
Posts: 5,351
For want of a better name: the HackerNAP board

One of the prototypes.

Group Buy is underway!

Working from home all day today has given me the chance to really crank this amp up for extended periods of time. I love it. I think you'll love it. No more messing around, let's start this GB properly!

As usual, it's payment in advance for the PCBs plus postage. Each board is $5 plus P&P at the following cost:

USA: $5
World: $9

That'll cover materials and actual postage costs. Any leftover cents will go to the pfm coffers.

To figure out how much to pay:
  • Take the number of boards you'd like and multiply by $5. Eg. 4 PCBs = $20
  • Add postage for your order. Eg. $9 to the UK + $20 = $29 for 4 boards posted to the UK.
  • Send payment via PayPal.
  • If you can't do a gift, please calculate the PayPal fees yourself (i'm too old and lazy for that!!)
  • Please please please put your REAL NAME and PFM alias somewhere in the payment subject or message. If you don't tell me your name and alias, you'll hold things up.
  • Make sure you provide a postal address!
  • As each pfm member pays, I'll put a check next to your name (not your real name, your pfm alias) on the first page of this thread.
  • Once either (a) everyone has paid, or (b) we get to Friday 30th of April, I'll close the group buy and place the order.
I'll place the order on Monday May 3rd unless everyone pays early, in which case I'll place the order early.


The latest schematic can be downloaded here. Like I said earlier it's a mix of NCC, Acoustica, and PD.


The latest BOM can be downloaded here.

Connection diagram

A diagram of how to wire this thing up to two separate power supplies can be found here. Note: the diagram assumes you're using HackerCAP PSU boards. If you're using anything else, I assume you know enough about what you're doing to not need a diagram.

Some background

My current power amp is made up of a dual-mono configuration consisting of heavily modified NCC clones off eBay, separate front-end and output stage transformers, separate VBEs for the front end, etc etc.

It was a pain in the arse to build and wire up. It also takes up too much space in the case.

I wanted to simplify things and, to that end, came up with a new layout for NAP-style power amp PCBs. They're the same size as Naim NAP boards (5" x 3.5") and borrow from the NCC circuit, the eBay clone circuit, Acoustica mods, and PD's FET-based VBE.

The PCB incorporates:

1. Pretty much the same audio circuit as the NCC200/eBay clones
2. TO-247 output transistors
3. Acoustica-style output transistor decoupling with on-board 470uF caps
3. Magic pixie dust
4. Well-sorted grounding
5. Big spaces for feedback caps (will accommodate MMKs and even 68uF Wima MKS4)
6. Big spaces for input coupling caps
7. Separate power inputs for front-end and output stage supplies
8. On-board FET-based VBE front-end power circuitry ala PigletsDad
9. Each of these amp boards is designed to be used with two of my poweramp rectifier PCBs, one for the front-end one for the output stage. The front-end requires 5 dedicated 0V returns, the output stage requires 4.

Grounding is carefully arranged so that the on-board 0V star is where all of the different 0V points meet, and is therefore the only common point for:

1. Audio 0V
2. Front-end supply 0V
3. Output stage supply 0V

The rest of the 0V points are labelled FE (front-end) or OP (output stage) to make it clear where each 0V return should be wired to.

Here's the board layout as it stands just now. It's pretty much done (although I'm considering a dedicated 0V return for the feedback cap to return to the front-end PSU board's 0V star), I'm just tidying up the BOM:

I was just going to have a handful made for my own personal use but figured I'd throw it out there: anyone else interested in some of these? Clearly they're only really of use to people building NAP-style amps with separate front-end regulation so I imagine there's a limited audience, but we'll see how much interest there is.



They're $5 per PCB plus postage and packing.


HackerCAP (haha, couldn't resist!) interest so far

You need 2 PSU boards per amplifier board. In other words, 4 PSU boards and 2 amplifier boards for a stereo power amp. See this thread for the power amp PSU PCB group buy.

Last edited by hacker; 17-05-10 at 03:13 AM.
Old 11-03-10, 09:11 PM
stackowax stackowax is offline
pfm Member
Join Date: Jul 2003
Posts: 1,626
I'm game.
Old 11-03-10, 10:03 PM
flashgo flashgo is offline
DIY Practitioner
Join Date: Jul 2008
Posts: 1,749
Originally Posted by hacker View Post
anyone else interested in some of these?
Thanks, Carl, I'll take 6 no, maybe 12!
Less is more, more is less
Old 11-03-10, 10:36 PM
flashgo flashgo is offline
DIY Practitioner
Join Date: Jul 2008
Posts: 1,749
Carl, I'm playing around with the 0.47uF Soviet polystyrenes that you pointed me to, and they make for very nice input couplers (with suitable choice of R). Would it be possible to shift the holes for C1 around a bit so that a big round radial cap could be fit?

Also, I'll likely regret this, but I might be willing to organize a GB for components. Of course, if you've got a Mouser shopping list set up, it's probably simpler for folks to just click the "buy this list" button and have Mouser do the work.
Less is more, more is less
Old 11-03-10, 10:45 PM
benzp benzp is offline
pfm Member
Join Date: Feb 2010
Posts: 53
Carl, Count me in.
Old 11-03-10, 11:05 PM
olpplo olpplo is offline
Join Date: Jun 2008
Posts: 67
Please, I'll take 4 board and related smoothing PCB.

Old 12-03-10, 12:22 AM
cromodora cromodora is offline
Join Date: Sep 2004
Posts: 1,182
It will be a first for a NAP type board if you can put the bias transistor on the same heatsink with the output trannies
Old 12-03-10, 12:28 AM
Bemused Bemused is offline
What's this all about then?
Join Date: Sep 2008
Posts: 7,337
Hi Carl, absolulty great work, looks mighty impressive.
I would be pleased to take four.
Old 12-03-10, 12:33 AM
Pete MB&D Pete MB&D is online now
Pete Maddex, the one and only!
Join Date: Jul 2003
Posts: 7,653

I will take a couple or 4 depending on the price, its about time I re-built my 135 clones.

Old 12-03-10, 12:50 AM
sq225917 sq225917 is offline
situation engineer
Join Date: Jun 2006
Posts: 19,296
Jesus I haven't finished my NCC's from Les yet.
Old 12-03-10, 01:17 AM
James Evans James Evans is offline
Bedroom Bodger
Join Date: Aug 2005
Posts: 5,194
Only just sodding bought my NCC boards as well.
Old 12-03-10, 01:21 AM
Uzinusa Uzinusa is offline
Happy Chappy
Join Date: May 2007
Posts: 3,450
Only just built my NCC200 as well...arse! I'm up for 4 though :-0
Old 12-03-10, 01:34 AM
Uzinusa Uzinusa is offline
Happy Chappy
Join Date: May 2007
Posts: 3,450
I feel a group-buy coming on
Old 12-03-10, 02:08 AM
Yank Yank is offline
Bulbous Also Tapered
Join Date: Sep 2009
Posts: 8,911
If we're doing a group buy, sign me up for a pair please.
Old 12-03-10, 02:19 AM
sam_cat sam_cat is online now
Join Date: Jan 2009
Posts: 3,642
Depending on cost I am interested in a pair of boards (maybe even 4).

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