PCB group buy advice needed.....
Nov 1, 2008 at 12:58 AM Thread Starter Post #1 of 4

69CamaroSS396

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I am considering organizing a group buy in the near future for the Pete Millett UniAmp. There was a source for this pcb, Euphonia Audio, which is now defunct. I have received email from Mr. Millett stating his approval of said GB. All he asks for is being notified of the GB if it takes place.

What I'm wanting is guidance from fellow DIYers as to what to expect as the organizer of a GB such as this, what pcb manufacturer to use, what kind of pcb do I want to order, i.e., what number of layers, etc.

The Gerber files are available on Mr. Millett's site. How do I go about using those in conjunction with the manufacturer, etc.?

Push-pull KT88 class A amp with "universal" driver PCB
 
Nov 1, 2008 at 2:04 AM Post #2 of 4

Nemo de Monet

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Well, if you're using the Gerber files from the site, some of your decisions are already made for you: it's a two-layer board of fixed, rectangular dimensions, with a single-side silkscreen. I would hazard a guess that board and copper thickness aren't super critical; "normal" is 1.6mm board and 1oz (35um) copper, though I'd prefer 2mm and 2oz/70um for something like this. What *you* use depends on what your chosen fab house can provide, and what you're willing to pay. You probably don't want to bother with gold-plating, fancy soldermask colors, or whatever; green soldermask, white silk-screening, and lead-free HASL plating are what you should be looking for, IMO. (You *can* do whatever you want - I have a set of BrianGT's mini-Aleph boards, which have black soldermask and gold plating, and while they're very nice touches, I feel they're really unnecessary expenses...)

Who you pick to make the boards is really a personal decision; if you're not comfortable using a Chinese business like Golden Phoenix (who do excellent work, incidentally), for example, there are a lot of domestic companies which charge (considerably!) more, but (are said to) deliver higher-quality products. I'd suggest getting quotes from as many outfits as you can, for however many boards you think you're going to need, and then a few. (Most of the time, you're looking at a "setup fee", and a per-board price, which goes down rapidly with quantity. It might set you back, say, $400 for 50 boards, but only $550 for 100 boards...) There are a couple sites that let you play around with online price calculators, to see how different things affect the cost; pcbcart.com is one, and makepcb.com is another.

I'm sure others can provide lots of dos and donts for the actual GB portion of things, but the sourcing of the PCB isn't terribly difficult; it just requires making choices without - necessarily - any "best" answers...
 
Nov 1, 2008 at 2:10 AM Post #3 of 4

tomb

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Attach the Gerber files in an e-mail requesting pricing to "sales@pcbnet.com". (Imagineering) Add information requesting "0.062" FRP, 2 oz. copper."

Pricing will probably go in quantities of 50, 100, 200, etc., although you may be able to get them in increments of 25. You'll need to make some sort of estimate based on how many you think will participate in the Group Buy, but then you can revise the price downward if you get more.

Don't forget to include shipping to you, shipping to the Group Buy purchaser, costs of boxing/envelopes, gas to the Post Office, Paypal fees, etc. when making up your price.
wink.gif


EDIT: Come to think of it, you might want to go quite a bit thicker on that board - 0.125" might be best.
 
Nov 1, 2008 at 1:24 PM Post #4 of 4

69CamaroSS396

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Thanks to both of you for the detailed info. Just what I was hoping for.

As if I don't already have enough projects I've been neglecting, I thought I'd add another or two for this winter. Ha! Ha!

Seriously, I'm no long time "expert", but I love Mr. Millett's very simple, uncomplicated designs. He is so NOT anal in his approach, it seems. His site has so much info, what with all the old manuals, books, etc., he has uploaded. He has layout examples and such things that can be so helpful to someone just starting this type of thing. I'm sure many reading this are already aware, but maybe some newbies are not.

Many things brought me to this particular design, but the ability to roll several different tube types with ease is an added attraction. I'm hoping to use socketed resistors to allow me to optimize each tube type a little better. Switch on the OPT for UL/triode.

Mr. Millett informed me that this pcb is available from a vendor in Italy. If the interest isn't enough to justify a GB, I'll probably try to get one from there, or just do a point to point amp. Not my favorite thing, but I have done a couple with success.

Audiocostruzioni - Il Portale dell'alta fedeltà amatoriale

Thanks again, Greg
 

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