Aleph-X Official PCB rev Beta & 1.0

[hifiZen]

OK, this is an update on the "unified" PCB design / purchase effort (separate from Carpenter's PCB fab run) from the Aleph-X thread.

Grataku has graciously offered his layout as the starting point for this design, and BrianGT has also offered to help with layout work. Grataku's layout is similar to tvi's (see previous posts in main Aleph-X thread to get an idea of what grataku's boards look like). The design at present includes most of the following features:

- absolute DC offset nulling resistors added (output to diff pair sources ala Ian)
- Local rail decoupling
- options for either Fred's current source, or Grey's (option for R17 to either ground or negative rail)
- footprints for stability capacitors will be included (may not be necessary, but they'll be there in case they're needed)
- maximum symmetry
- back-to-back diff pair for thermal coupling
- optimized grounding scheme
- two transistors on each end of the board (like tvi's layout), all facing up so they can be mounted to a non-flanged heatsink as well as the Conrad Engineering double-flanged MF30 series heatsinks

These were the list of features members have requested so far. If you have anything else you'd like to add to the "wish list" please post or email me soon!

The plan at this point is to start by prototyping (rev. Beta) grataku's design at expresspcb.com. These boards will be available very soon, probably in about a week or so. After the proto boards are fabbed, then we will have some time to build and test while I copy the design into Protel, and do a the Gerber/NCD file generation for the professional fab house. Once rev Beta is tested and refinements are made, rev. 1.0 will go out for the main order.

The large order will probably go to Advanced Circuits for fab. They are a professional fab house, with excellent equipment and tight tolerances. The boards which emerge will be production quality, with the following features:

- Double sided
- extra-heavy 2oz. copper (heavier available, up to 4oz at greater cost)
- plated through-holes
- high quality LPI (photo-printed) solder mask, both sides
- single side silkscreen
- 3 x 4.5 inch dimensions (based on tvi's compact board layout)
- routered edges, not sheared or sawn

These will be top-of-the-line cadillac boards!

Pricing is roughly:
20pcs: $24 each
30pcs: $16 each
40pcs: $12 each
50pcs: $10 each

Shipping costs are additional. The current order count I have is about 26 boards. This number should increase as more people come on board (pun fully intended ). Tentative timeline for delivery of the rev. 1.0 boards is pre- Christmas. We'll see how it goes and take it one step at a time - I hope we can get there sooner.

[Edwin Dorre]

Hi,

Sorry if I look stupid while asking this. But reading 1000 replies on the X-aleph thread to get this answer....

Will this new board support higher biases (multiple mosfet's per stage)? for example a XA100 ?

Edwin

[Taco]

I don't know yet which board I need, this one or the carpenter board. I haven't the other parts yet, so time is not an issue. Also I am not sure what to build the Aleph 30 or the Aleph-X. I think the Aleph-X is better. I looked at the orginal circuit of Grollins, and the complexity of both circuits is of the same order to construct (O(n) ).

Some advice on what board to choose?

[MEnsing]

Edwin,

Why must the pcb support this? You can mount the output devices on a separate output board like an Aleph 2

[HBarske]

- single side silkscreen

Isn't that a bit unusual on a two layer board?

[Fred Dieckmann]

Just the opposite! The silkscreen shows the location, outline, polarity,and refererence designators for stuffing the parts. For parts mounted on only one side of the board it is the standard approach. The only double silkscreens I recall seeing were for mounting SMT parts to both sides of the PCB.

Fred

[Edwin Dorre]

Originally posted by MEnsing
Edwin,

Why must the pcb support this? You can mount the output devices on a separate output board like an Aleph 2

yeah, that's what I meant. Does the board support for more than 1 mosfet for each part (currentsink, current-source). As I like to build a XA100... As you need to have more and/or bigger resistors ...

Edwin

[Eric]

I was wondering about the same thing: scalability. Will the board feature a specific number of mosfets, or will it more like an Aleph design where the input stage and output stage are not part of the same board. In this manner, it seems that, like an Aleph, I could build an amp to suit my specific power needs and heat concerns.

[grataku]

Hi,
To Whoever requested the mother-daugther boards let me clarify how I see this effort, maybe HiFiZen and John would like to add or subtract from what I am saying: we are shooting for an alephX between aleph3 and 5 in terms of power. The times are not mature yet for a universal, high power AlephX. This is not a 'kit' either, it's just a non-profit (people that don't believe that should call Nelson lawyers for more in depth explanation) effort between a group of friends making something beautiful for a reasonable price and having a lot of fun in the process.

What we need to do right now is prototype, that includes testing the layout correctness, Fred CCS, DC offset, turn on-off transient, GROUNDS-trafo flux noises ETC, ETC. Adding outboard wiring and little boards flying all over the place is not going to help at this stage of the game.
If all goes well with prototyping the project may go on to higher powers and bigger and better things, but the foundations need to be solid for that to happen.

We are looking for is at least 10 volunteers willing to jump into prototyping for about $20? dollars a board or less. We have about 3 to 4 at this point, I think. After 15 production boards (to be used as prototypes) may become more convenient than prototypes at least with expresspcb.
Interested parties should send an email to Chad (HiFZen) which is the coordinator.

thank you

[Peter Daniel]

I think it might be a good idea to design one board with 4 output devices (like Grey's version). It should be able to provide around 40-50W which is plenty for bi-amping or tri-amping, or for home theatre purposes. More output devices on a single board will complicate the layout. Now, if somebody wants still to use this board with more power and more output FETs, all he has to do is to use separate output board or p2p technique and use the universal board only for front end without output FETs.